package org.hl7.fhir.r4.utils;

//import ca.uhn.fhir.model.api.TemporalPrecisionEnum;

import ca.uhn.fhir.model.api.TemporalPrecisionEnum;
import ca.uhn.fhir.util.ElementUtil;
import org.apache.commons.lang3.NotImplementedException;
import org.fhir.ucum.Decimal;
import org.fhir.ucum.Pair;
import org.fhir.ucum.UcumException;
import org.hl7.fhir.exceptions.DefinitionException;
import org.hl7.fhir.exceptions.FHIRException;
import org.hl7.fhir.exceptions.PathEngineException;
import org.hl7.fhir.r4.conformance.ProfileUtilities;
import org.hl7.fhir.r4.context.IWorkerContext;
import org.hl7.fhir.r4.model.*;
import org.hl7.fhir.r4.model.ElementDefinition.TypeRefComponent;
import org.hl7.fhir.r4.model.ExpressionNode.*;
import org.hl7.fhir.r4.model.StructureDefinition.StructureDefinitionKind;
import org.hl7.fhir.r4.model.StructureDefinition.TypeDerivationRule;
import org.hl7.fhir.r4.model.TypeDetails.ProfiledType;
import org.hl7.fhir.r4.utils.FHIRLexer.FHIRLexerException;
import org.hl7.fhir.r4.utils.FHIRPathEngine.IEvaluationContext.FunctionDetails;
import org.hl7.fhir.utilities.Utilities;

import java.math.BigDecimal;
import java.util.*;

/**
 * @author Grahame Grieve
 */
public class FHIRPathEngine {
  private IWorkerContext worker;
  private IEvaluationContext hostServices;
  private StringBuilder log = new StringBuilder();
  private Set<String> primitiveTypes = new HashSet<String>();
  private Map<String, StructureDefinition> allTypes = new HashMap<String, StructureDefinition>();
  /**
   * @param worker - used when validating paths (@check), and used doing value set membership when executing tests (once that's defined)
   */
  public FHIRPathEngine(IWorkerContext worker) {
    super();
    this.worker = worker;
    for (StructureDefinition sd : worker.allStructures()) {
      if (sd.getDerivation() == TypeDerivationRule.SPECIALIZATION && sd.getKind() != StructureDefinitionKind.LOGICAL)
        allTypes.put(sd.getName(), sd);
      if (sd.getDerivation() == TypeDerivationRule.SPECIALIZATION && sd.getKind() == StructureDefinitionKind.PRIMITIVETYPE) {
        primitiveTypes.add(sd.getName());
      }
    }
  }

  private TypeDetails anything(CollectionStatus status) {
    return new TypeDetails(status, allTypes.keySet());
  }

  private ExecutionContext changeThis(ExecutionContext context, Base newThis) {
    return new ExecutionContext(context.appInfo, context.resource, context.context, context.aliases, newThis);
  }

  private ExecutionTypeContext changeThis(ExecutionTypeContext context, TypeDetails newThis) {
    return new ExecutionTypeContext(context.appInfo, context.resource, context.context, newThis);
  }


  // --- 3 methods to override in children -------------------------------------------------------
  // if you don't override, it falls through to the using the base reference implementation 
  // HAPI overrides to these to support extending the base model

  /**
   * check that paths referred to in the ExpressionNode are valid
   * <p>
   * xPathStartsWithValueRef is a hack work around for the fact that FHIR Path sometimes needs a different starting point than the xpath
   * <p>
   * returns a list of the possible types that might be returned by executing the ExpressionNode against a particular context
   *
   * @param context - the logical type against which this path is applied
   * @throws DefinitionException
   * @throws PathEngineException
   * @if the path is not valid
   */
  public TypeDetails check(Object appContext, String resourceType, String context, ExpressionNode expr) throws FHIRLexerException, PathEngineException, DefinitionException {
    // if context is a path that refers to a type, do that conversion now
    TypeDetails types;
    if (context == null) {
      types = null; // this is a special case; the first path reference will have to resolve to something in the context
    } else if (!context.contains(".")) {
      StructureDefinition sd = worker.fetchResource(StructureDefinition.class, context);
      types = new TypeDetails(CollectionStatus.SINGLETON, sd.getUrl());
    } else {
      String ctxt = context.substring(0, context.indexOf('.'));
      if (Utilities.isAbsoluteUrl(resourceType)) {
        ctxt = resourceType.substring(0, resourceType.lastIndexOf("/") + 1) + ctxt;
      }
      StructureDefinition sd = worker.fetchResource(StructureDefinition.class, ctxt);
      if (sd == null)
        throw new PathEngineException("Unknown context " + context);
      ElementDefinitionMatch ed = getElementDefinition(sd, context, true);
      if (ed == null)
        throw new PathEngineException("Unknown context element " + context);
      if (ed.fixedType != null)
        types = new TypeDetails(CollectionStatus.SINGLETON, ed.fixedType);
      else if (ed.getDefinition().getType().isEmpty() || isAbstractType(ed.getDefinition().getType()))
        types = new TypeDetails(CollectionStatus.SINGLETON, ctxt + "#" + context);
      else {
        types = new TypeDetails(CollectionStatus.SINGLETON);
        for (TypeRefComponent t : ed.getDefinition().getType())
          types.addType(t.getCode());
      }
    }

    return executeType(new ExecutionTypeContext(appContext, resourceType, context, types), types, expr, true);
  }

  public TypeDetails check(Object appContext, StructureDefinition sd, String context, ExpressionNode expr) throws FHIRLexerException, PathEngineException, DefinitionException {
    // if context is a path that refers to a type, do that conversion now
    TypeDetails types;
    if (!context.contains(".")) {
      types = new TypeDetails(CollectionStatus.SINGLETON, sd.getUrl());
    } else {
      ElementDefinitionMatch ed = getElementDefinition(sd, context, true);
      if (ed == null)
        throw new PathEngineException("Unknown context element " + context);
      if (ed.fixedType != null)
        types = new TypeDetails(CollectionStatus.SINGLETON, ed.fixedType);
      else if (ed.getDefinition().getType().isEmpty() || isAbstractType(ed.getDefinition().getType()))
        types = new TypeDetails(CollectionStatus.SINGLETON, sd.getUrl() + "#" + context);
      else {
        types = new TypeDetails(CollectionStatus.SINGLETON);
        for (TypeRefComponent t : ed.getDefinition().getType())
          types.addType(t.getCode());
      }
    }

    return executeType(new ExecutionTypeContext(appContext, sd.getUrl(), context, types), types, expr, true);
  }

  public TypeDetails check(Object appContext, StructureDefinition sd, ExpressionNode expr) throws FHIRLexerException, PathEngineException, DefinitionException {
    // if context is a path that refers to a type, do that conversion now
    TypeDetails types = null; // this is a special case; the first path reference will have to resolve to something in the context
    return executeType(new ExecutionTypeContext(appContext, sd == null ? null : sd.getUrl(), null, types), types, expr, true);
  }

  // --- public API -------------------------------------------------------

  public TypeDetails check(Object appContext, String resourceType, String context, String expr) throws FHIRLexerException, PathEngineException, DefinitionException {
    return check(appContext, resourceType, context, parse(expr));
  }

  private void checkContextCoded(TypeDetails focus, String name) throws PathEngineException {
    if (!focus.hasType(worker, "string") && !focus.hasType(worker, "code") && !focus.hasType(worker, "uri") && !focus.hasType(worker, "Coding") && !focus.hasType(worker, "CodeableConcept"))
      throw new PathEngineException("The function '" + name + "'() can only be used on string, code, uri, Coding, CodeableConcept");
  }

  private void checkContextPrimitive(TypeDetails focus, String name, boolean canQty) throws PathEngineException {
    if (canQty) {
      if (!focus.hasType(primitiveTypes) && !focus.hasType("Quantity"))
        throw new PathEngineException("The function '" + name + "'() can only be used on a Quantity or on " + primitiveTypes.toString());
    } else if (!focus.hasType(primitiveTypes))
      throw new PathEngineException("The function '" + name + "'() can only be used on " + primitiveTypes.toString());
  }

  private void checkContextReference(TypeDetails focus, String name) throws PathEngineException {
    if (!focus.hasType(worker, "string") && !focus.hasType(worker, "uri") && !focus.hasType(worker, "Reference") && !focus.hasType(worker, "canonical"))
      throw new PathEngineException("The function '" + name + "'() can only be used on string, uri, canonical, Reference");
  }

  private void checkContextString(TypeDetails focus, String name) throws PathEngineException {
    if (!focus.hasType(worker, "string") && !focus.hasType(worker, "code") && !focus.hasType(worker, "uri") && !focus.hasType(worker, "id"))
      throw new PathEngineException("The function '" + name + "'() can only be used on string, uri, code, id, but found " + focus.describe());
  }

  private void checkOrdered(TypeDetails focus, String name) throws PathEngineException {
    if (focus.getCollectionStatus() == CollectionStatus.UNORDERED)
      throw new PathEngineException("The function '" + name + "'() can only be used on ordered collections");
  }

  private boolean checkParamCount(FHIRLexer lexer, SourceLocation location, ExpressionNode exp, int count) throws FHIRLexerException {
    if (exp.getParameters().size() != count)
      throw lexer.error("The function \"" + exp.getName() + "\" requires " + Integer.toString(count) + " parameters", location.toString());
    return true;
  }

  private boolean checkParamCount(FHIRLexer lexer, SourceLocation location, ExpressionNode exp, int countMin, int countMax) throws FHIRLexerException {
    if (exp.getParameters().size() < countMin || exp.getParameters().size() > countMax)
      throw lexer.error("The function \"" + exp.getName() + "\" requires between " + Integer.toString(countMin) + " and " + Integer.toString(countMax) + " parameters", location.toString());
    return true;
  }

  private void checkParamTypes(String funcName, List<TypeDetails> paramTypes, TypeDetails... typeSet) throws PathEngineException {
    int i = 0;
    for (TypeDetails pt : typeSet) {
      if (i == paramTypes.size())
        return;
      TypeDetails actual = paramTypes.get(i);
      i++;
      for (String a : actual.getTypes()) {
        if (!pt.hasType(worker, a))
          throw new PathEngineException("The parameter type '" + a + "' is not legal for " + funcName + " parameter " + Integer.toString(i) + ". expecting " + pt.toString());
      }
    }
  }

  private boolean checkParameters(FHIRLexer lexer, SourceLocation location, ExpressionNode exp, FunctionDetails details) throws FHIRLexerException {
    switch (exp.getFunction()) {
      case Empty:
        return checkParamCount(lexer, location, exp, 0);
      case Not:
        return checkParamCount(lexer, location, exp, 0);
      case Exists:
        return checkParamCount(lexer, location, exp, 0);
      case SubsetOf:
        return checkParamCount(lexer, location, exp, 1);
      case SupersetOf:
        return checkParamCount(lexer, location, exp, 1);
      case IsDistinct:
        return checkParamCount(lexer, location, exp, 0);
      case Distinct:
        return checkParamCount(lexer, location, exp, 0);
      case Count:
        return checkParamCount(lexer, location, exp, 0);
      case Where:
        return checkParamCount(lexer, location, exp, 1);
      case Select:
        return checkParamCount(lexer, location, exp, 1);
      case All:
        return checkParamCount(lexer, location, exp, 0, 1);
      case Repeat:
        return checkParamCount(lexer, location, exp, 1);
      case Aggregate:
        return checkParamCount(lexer, location, exp, 1, 2);
      case Item:
        return checkParamCount(lexer, location, exp, 1);
      case As:
        return checkParamCount(lexer, location, exp, 1);
      case OfType:
        return checkParamCount(lexer, location, exp, 1);
      case Type:
        return checkParamCount(lexer, location, exp, 0);
      case Is:
        return checkParamCount(lexer, location, exp, 1);
      case Single:
        return checkParamCount(lexer, location, exp, 0);
      case First:
        return checkParamCount(lexer, location, exp, 0);
      case Last:
        return checkParamCount(lexer, location, exp, 0);
      case Tail:
        return checkParamCount(lexer, location, exp, 0);
      case Skip:
        return checkParamCount(lexer, location, exp, 1);
      case Take:
        return checkParamCount(lexer, location, exp, 1);
      case Union:
        return checkParamCount(lexer, location, exp, 1);
      case Combine:
        return checkParamCount(lexer, location, exp, 1);
      case Intersect:
        return checkParamCount(lexer, location, exp, 1);
      case Exclude:
        return checkParamCount(lexer, location, exp, 1);
      case Iif:
        return checkParamCount(lexer, location, exp, 2, 3);
      case Lower:
        return checkParamCount(lexer, location, exp, 0);
      case Upper:
        return checkParamCount(lexer, location, exp, 0);
      case ToChars:
        return checkParamCount(lexer, location, exp, 0);
      case Substring:
        return checkParamCount(lexer, location, exp, 1, 2);
      case StartsWith:
        return checkParamCount(lexer, location, exp, 1);
      case EndsWith:
        return checkParamCount(lexer, location, exp, 1);
      case Matches:
        return checkParamCount(lexer, location, exp, 1);
      case ReplaceMatches:
        return checkParamCount(lexer, location, exp, 2);
      case Contains:
        return checkParamCount(lexer, location, exp, 1);
      case Replace:
        return checkParamCount(lexer, location, exp, 2);
      case Length:
        return checkParamCount(lexer, location, exp, 0);
      case Children:
        return checkParamCount(lexer, location, exp, 0);
      case Descendants:
        return checkParamCount(lexer, location, exp, 0);
      case MemberOf:
        return checkParamCount(lexer, location, exp, 1);
      case Trace:
        return checkParamCount(lexer, location, exp, 1);
      case Today:
        return checkParamCount(lexer, location, exp, 0);
      case Now:
        return checkParamCount(lexer, location, exp, 0);
      case Resolve:
        return checkParamCount(lexer, location, exp, 0);
      case Extension:
        return checkParamCount(lexer, location, exp, 1);
      case HasValue:
        return checkParamCount(lexer, location, exp, 0);
      case Alias:
        return checkParamCount(lexer, location, exp, 1);
      case AliasAs:
        return checkParamCount(lexer, location, exp, 1);
      case HtmlChecks:
        return checkParamCount(lexer, location, exp, 0);
      case ToInteger:
        return checkParamCount(lexer, location, exp, 0);
      case ToDecimal:
        return checkParamCount(lexer, location, exp, 0);
      case ToString:
        return checkParamCount(lexer, location, exp, 0);
      case ToQuantity:
        return checkParamCount(lexer, location, exp, 0);
      case ToBoolean:
        return checkParamCount(lexer, location, exp, 0);
      case ToDateTime:
        return checkParamCount(lexer, location, exp, 0);
      case ToTime:
        return checkParamCount(lexer, location, exp, 0);
      case IsInteger:
        return checkParamCount(lexer, location, exp, 0);
      case IsDecimal:
        return checkParamCount(lexer, location, exp, 0);
      case IsString:
        return checkParamCount(lexer, location, exp, 0);
      case IsQuantity:
        return checkParamCount(lexer, location, exp, 0);
      case IsBoolean:
        return checkParamCount(lexer, location, exp, 0);
      case IsDateTime:
        return checkParamCount(lexer, location, exp, 0);
      case IsTime:
        return checkParamCount(lexer, location, exp, 0);
      case Custom:
        return checkParamCount(lexer, location, exp, details.getMinParameters(), details.getMaxParameters());
    }
    return false;
  }

  private TypeDetails childTypes(TypeDetails focus, String mask) throws PathEngineException, DefinitionException {
    TypeDetails result = new TypeDetails(CollectionStatus.UNORDERED);
    for (String f : focus.getTypes())
      getChildTypesByName(f, mask, result);
    return result;
  }

  private int compareDateTimeElements(Base theL, Base theR, boolean theEquivalenceTest) {
    String dateLeftString = theL.primitiveValue();
    DateTimeType dateLeft = new DateTimeType(dateLeftString);

    String dateRightString = theR.primitiveValue();
    DateTimeType dateRight = new DateTimeType(dateRightString);

    if (theEquivalenceTest) {
      TemporalPrecisionEnum lowestPrecision = dateLeft.getPrecision().ordinal() < dateRight.getPrecision().ordinal() ? dateLeft.getPrecision() : dateRight.getPrecision();
      dateLeft.setPrecision(lowestPrecision);
      dateRight.setPrecision(lowestPrecision);
    }

    if (dateLeft.getPrecision().ordinal() > TemporalPrecisionEnum.DAY.ordinal()) {
      dateLeft.setTimeZoneZulu(true);
    }
    if (dateRight.getPrecision().ordinal() > TemporalPrecisionEnum.DAY.ordinal()) {
      dateRight.setTimeZoneZulu(true);
    }

    dateLeftString = dateLeft.getValueAsString();
    dateRightString = dateRight.getValueAsString();

    return dateLeftString.compareTo(dateRightString);
  }

  /**
   * worker routine for converting a set of objects to a boolean representation (for invariants)
   *
   * @param items - result from @evaluate
   * @return
   */
  public boolean convertToBoolean(List<Base> items) {
    if (items == null)
      return false;
    else if (items.size() == 1 && items.get(0) instanceof BooleanType)
      return ((BooleanType) items.get(0)).getValue();
    else if (items.size() == 1 && items.get(0).isBooleanPrimitive()) // element model
      return Boolean.valueOf(items.get(0).primitiveValue());
    else
      return items.size() > 0;
  }

  /**
   * worker routine for converting a set of objects to a string representation
   *
   * @param items - result from @evaluate
   * @return
   */
  public String convertToString(List<Base> items) {
    StringBuilder b = new StringBuilder();
    boolean first = true;
    for (Base item : items) {
      if (first)
        first = false;
      else
        b.append(',');

      b.append(convertToString(item));
    }
    return b.toString();
  }

  private String convertToString(Base item) {
    if (item.isPrimitive())
      return item.primitiveValue();
    else if (item instanceof Quantity) {
      Quantity q = (Quantity) item;
      if (q.getSystem().equals("http://unitsofmeasure.org")) {
        String u = "'" + q.getCode() + "'";
        boolean plural = !q.getValue().toPlainString().equals("1");
        if ("a".equals(q.getCode()))
          u = plural ? "years" : "year";
        else if ("mo".equals(q.getCode()))
          u = plural ? "months" : "month";
        else if ("wk".equals(q.getCode()))
          u = plural ? "weeks" : "week";
        else if ("d".equals(q.getCode()))
          u = plural ? "days" : "day";
        else if ("h".equals(q.getCode()))
          u = plural ? "hours" : "hour";
        else if ("min".equals(q.getCode()))
          u = plural ? "minutes" : "minute";
        else if ("s".equals(q.getCode()))
          u = plural ? "seconds" : "seconds";
        else if ("ms".equals(q.getCode()))
          u = plural ? "milliseconds" : "milliseconds";
        return q.getValue().toPlainString() + " " + u;
      } else
        return item.toString();
    } else
      return item.toString();
  }

  private boolean doContains(List<Base> list, Base item) {
    for (Base test : list)
      if (doEquals(test, item))
        return true;
    return false;
  }

  private boolean doEquals(Base left, Base right) {
    if (left instanceof Quantity && right instanceof Quantity)
      return qtyEqual((Quantity) left, (Quantity) right);
    else if (left.isPrimitive() && right.isPrimitive())
      return Base.equals(left.primitiveValue(), right.primitiveValue());
    else
      return Base.compareDeep(left, right, false);
  }

  private boolean doEquivalent(Base left, Base right) throws PathEngineException {
    if (left instanceof Quantity && right instanceof Quantity)
      return qtyEquivalent((Quantity) left, (Quantity) right);
    if (left.hasType("integer") && right.hasType("integer"))
      return doEquals(left, right);
    if (left.hasType("boolean") && right.hasType("boolean"))
      return doEquals(left, right);
    if (left.hasType("integer", "decimal", "unsignedInt", "positiveInt") && right.hasType("integer", "decimal", "unsignedInt", "positiveInt"))
      return Utilities.equivalentNumber(left.primitiveValue(), right.primitiveValue());
    if (left.hasType("date", "dateTime", "time", "instant") && right.hasType("date", "dateTime", "time", "instant"))
      return compareDateTimeElements(left, right, true) == 0;
    if (left.hasType("string", "id", "code", "uri") && right.hasType("string", "id", "code", "uri"))
      return Utilities.equivalent(convertToString(left), convertToString(right));

    throw new PathEngineException(String.format("Unable to determine equivalence between %s and %s", left.fhirType(), right.fhirType()));
  }

  /**
   * evaluate a path and return the matching elements
   *
   * @param base           - the object against which the path is being evaluated
   * @param ExpressionNode - the parsed ExpressionNode statement to use
   * @return
   * @throws FHIRException
   * @
   */
  public List<Base> evaluate(Base base, ExpressionNode ExpressionNode) throws FHIRException {
    List<Base> list = new ArrayList<Base>();
    if (base != null)
      list.add(base);
    log = new StringBuilder();
    return execute(new ExecutionContext(null, base != null && base.isResource() ? base : null, base, null, base), list, ExpressionNode, true);
  }

  /**
   * evaluate a path and return the matching elements
   *
   * @param base - the object against which the path is being evaluated
   * @param path - the FHIR Path statement to use
   * @return
   * @throws FHIRException
   * @
   */
  public List<Base> evaluate(Base base, String path) throws FHIRException {
    ExpressionNode exp = parse(path);
    List<Base> list = new ArrayList<Base>();
    if (base != null)
      list.add(base);
    log = new StringBuilder();
    return execute(new ExecutionContext(null, base.isResource() ? base : null, base, null, base), list, exp, true);
  }

  /**
   * evaluate a path and return the matching elements
   *
   * @param base           - the object against which the path is being evaluated
   * @param ExpressionNode - the parsed ExpressionNode statement to use
   * @return
   * @throws FHIRException
   * @
   */
  public List<Base> evaluate(Object appContext, Resource resource, Base base, ExpressionNode ExpressionNode) throws FHIRException {
    List<Base> list = new ArrayList<Base>();
    if (base != null)
      list.add(base);
    log = new StringBuilder();
    return execute(new ExecutionContext(appContext, resource, base, null, base), list, ExpressionNode, true);
  }

  /**
   * evaluate a path and return the matching elements
   *
   * @param base           - the object against which the path is being evaluated
   * @param ExpressionNode - the parsed ExpressionNode statement to use
   * @return
   * @throws FHIRException
   * @
   */
  public List<Base> evaluate(Object appContext, Base resource, Base base, ExpressionNode ExpressionNode) throws FHIRException {
    List<Base> list = new ArrayList<Base>();
    if (base != null)
      list.add(base);
    log = new StringBuilder();
    return execute(new ExecutionContext(appContext, resource, base, null, base), list, ExpressionNode, true);
  }

  /**
   * evaluate a path and return the matching elements
   *
   * @param base - the object against which the path is being evaluated
   * @param path - the FHIR Path statement to use
   * @return
   * @throws FHIRException
   * @
   */
  public List<Base> evaluate(Object appContext, Resource resource, Base base, String path) throws FHIRException {
    ExpressionNode exp = parse(path);
    List<Base> list = new ArrayList<Base>();
    if (base != null)
      list.add(base);
    log = new StringBuilder();
    return execute(new ExecutionContext(appContext, resource, base, null, base), list, exp, true);
  }

  /**
   * given an element definition in a profile, what element contains the differentiating fixed
   * for the element, given the differentiating expresssion. The expression is only allowed to
   * use a subset of FHIRPath
   *
   * @param profile
   * @param element
   * @return
   * @throws PathEngineException
   * @throws DefinitionException
   */
  public ElementDefinition evaluateDefinition(ExpressionNode expr, StructureDefinition profile, ElementDefinition element) throws DefinitionException {
    StructureDefinition sd = profile;
    ElementDefinition focus = null;

    if (expr.getKind() == Kind.Name) {
      List<ElementDefinition> childDefinitions;
      childDefinitions = ProfileUtilities.getChildMap(sd, element);
      // if that's empty, get the children of the type
      if (childDefinitions.isEmpty()) {
        sd = fetchStructureByType(element);
        if (sd == null)
          throw new DefinitionException("Problem with use of resolve() - profile '" + element.getType().get(0).getProfile() + "' on " + element.getId() + " could not be resolved");
        childDefinitions = ProfileUtilities.getChildMap(sd, sd.getSnapshot().getElementFirstRep());
      }
      for (ElementDefinition t : childDefinitions) {
        if (tailMatches(t, expr.getName())) {
          focus = t;
          break;
        }
      }
    } else if (expr.getKind() == Kind.Function) {
      if ("resolve".equals(expr.getName())) {
        if (!element.hasType())
          throw new DefinitionException("illegal use of resolve() in discriminator - no type on element " + element.getId());
        if (element.getType().size() > 1)
          throw new DefinitionException("illegal use of resolve() in discriminator - Multiple possible types on " + element.getId());
        if (!element.getType().get(0).hasTarget())
          throw new DefinitionException("illegal use of resolve() in discriminator - type on " + element.getId() + " is not Reference (" + element.getType().get(0).getCode() + ")");
        if (element.getType().get(0).getTargetProfile().size() > 1)
          throw new DefinitionException("illegal use of resolve() in discriminator - Multiple possible target type profiles on " + element.getId());
        sd = worker.fetchResource(StructureDefinition.class, element.getType().get(0).getTargetProfile().get(0).getValue());
        if (sd == null)
          throw new DefinitionException("Problem with use of resolve() - profile '" + element.getType().get(0).getTargetProfile() + "' on " + element.getId() + " could not be resolved");
        focus = sd.getSnapshot().getElementFirstRep();
      } else if ("extension".equals(expr.getName())) {
        String targetUrl = expr.getParameters().get(0).getConstant().primitiveValue();
//        targetUrl = targetUrl.substring(1,targetUrl.length()-1);
        List<ElementDefinition> childDefinitions = ProfileUtilities.getChildMap(sd, element);
        for (ElementDefinition t : childDefinitions) {
          if (t.getPath().endsWith(".extension") && t.hasSliceName()) {
            sd = worker.fetchResource(StructureDefinition.class, t.getType().get(0).getProfile().get(0).getValue());
            while (sd != null && !sd.getBaseDefinition().equals("http://hl7.org/fhir/StructureDefinition/Extension"))
              sd = worker.fetchResource(StructureDefinition.class, sd.getBaseDefinition());
            if (sd.getUrl().equals(targetUrl)) {
              focus = t;
              break;
            }
          }
        }
      } else
        throw new DefinitionException("illegal function name " + expr.getName() + "() in discriminator");
    } else if (expr.getKind() == Kind.Group) {
      throw new DefinitionException("illegal expression syntax in discriminator (group)");
    } else if (expr.getKind() == Kind.Constant) {
      throw new DefinitionException("illegal expression syntax in discriminator (const)");
    }

    if (focus == null)
      throw new DefinitionException("Unable to resolve discriminator");
    else if (expr.getInner() == null)
      return focus;
    else
      return evaluateDefinition(expr.getInner(), sd, focus);
  }

  private List<Base> evaluateFunction(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    switch (exp.getFunction()) {
      case Empty:
        return funcEmpty(context, focus, exp);
      case Not:
        return funcNot(context, focus, exp);
      case Exists:
        return funcExists(context, focus, exp);
      case SubsetOf:
        return funcSubsetOf(context, focus, exp);
      case SupersetOf:
        return funcSupersetOf(context, focus, exp);
      case IsDistinct:
        return funcIsDistinct(context, focus, exp);
      case Distinct:
        return funcDistinct(context, focus, exp);
      case Count:
        return funcCount(context, focus, exp);
      case Where:
        return funcWhere(context, focus, exp);
      case Select:
        return funcSelect(context, focus, exp);
      case All:
        return funcAll(context, focus, exp);
      case Repeat:
        return funcRepeat(context, focus, exp);
      case Aggregate:
        return funcAggregate(context, focus, exp);
      case Item:
        return funcItem(context, focus, exp);
      case As:
        return funcAs(context, focus, exp);
      case OfType:
        return funcAs(context, focus, exp);
      case Type:
        return funcType(context, focus, exp);
      case Is:
        return funcIs(context, focus, exp);
      case Single:
        return funcSingle(context, focus, exp);
      case First:
        return funcFirst(context, focus, exp);
      case Last:
        return funcLast(context, focus, exp);
      case Tail:
        return funcTail(context, focus, exp);
      case Skip:
        return funcSkip(context, focus, exp);
      case Take:
        return funcTake(context, focus, exp);
      case Union:
        return funcUnion(context, focus, exp);
      case Combine:
        return funcCombine(context, focus, exp);
      case Intersect:
        return funcIntersect(context, focus, exp);
      case Exclude:
        return funcExclude(context, focus, exp);
      case Iif:
        return funcIif(context, focus, exp);
      case Lower:
        return funcLower(context, focus, exp);
      case Upper:
        return funcUpper(context, focus, exp);
      case ToChars:
        return funcToChars(context, focus, exp);
      case Substring:
        return funcSubstring(context, focus, exp);
      case StartsWith:
        return funcStartsWith(context, focus, exp);
      case EndsWith:
        return funcEndsWith(context, focus, exp);
      case Matches:
        return funcMatches(context, focus, exp);
      case ReplaceMatches:
        return funcReplaceMatches(context, focus, exp);
      case Contains:
        return funcContains(context, focus, exp);
      case Replace:
        return funcReplace(context, focus, exp);
      case Length:
        return funcLength(context, focus, exp);
      case Children:
        return funcChildren(context, focus, exp);
      case Descendants:
        return funcDescendants(context, focus, exp);
      case MemberOf:
        return funcMemberOf(context, focus, exp);
      case Trace:
        return funcTrace(context, focus, exp);
      case Today:
        return funcToday(context, focus, exp);
      case Now:
        return funcNow(context, focus, exp);
      case Resolve:
        return funcResolve(context, focus, exp);
      case Extension:
        return funcExtension(context, focus, exp);
      case HasValue:
        return funcHasValue(context, focus, exp);
      case AliasAs:
        return funcAliasAs(context, focus, exp);
      case Alias:
        return funcAlias(context, focus, exp);
      case HtmlChecks:
        return funcHtmlChecks(context, focus, exp);
      case ToInteger:
        return funcToInteger(context, focus, exp);
      case ToDecimal:
        return funcToDecimal(context, focus, exp);
      case ToString:
        return funcToString(context, focus, exp);
      case ToBoolean:
        return funcToBoolean(context, focus, exp);
      case ToQuantity:
        return funcToQuantity(context, focus, exp);
      case ToDateTime:
        return funcToDateTime(context, focus, exp);
      case ToTime:
        return funcToTime(context, focus, exp);
      case IsInteger:
        return funcIsInteger(context, focus, exp);
      case IsDecimal:
        return funcIsDecimal(context, focus, exp);
      case IsString:
        return funcIsString(context, focus, exp);
      case IsBoolean:
        return funcIsBoolean(context, focus, exp);
      case IsQuantity:
        return funcIsQuantity(context, focus, exp);
      case IsDateTime:
        return funcIsDateTime(context, focus, exp);
      case IsTime:
        return funcIsTime(context, focus, exp);
      case Custom: {
        List<List<Base>> params = new ArrayList<List<Base>>();
        for (ExpressionNode p : exp.getParameters())
          params.add(execute(context, focus, p, true));
        return hostServices.executeFunction(context.appInfo, exp.getName(), params);
      }
      default:
        throw new Error("not Implemented yet");
    }
  }

  @SuppressWarnings("unchecked")
  private TypeDetails evaluateFunctionType(ExecutionTypeContext context, TypeDetails focus, ExpressionNode exp) throws PathEngineException, DefinitionException {
    List<TypeDetails> paramTypes = new ArrayList<TypeDetails>();
    if (exp.getFunction() == Function.Is || exp.getFunction() == Function.As)
      paramTypes.add(new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
    else
      for (ExpressionNode expr : exp.getParameters()) {
        if (exp.getFunction() == Function.Where || exp.getFunction() == Function.Select || exp.getFunction() == Function.Repeat || exp.getFunction() == Function.Aggregate)
          paramTypes.add(executeType(changeThis(context, focus), focus, expr, true));
        else
          paramTypes.add(executeType(context, focus, expr, true));
      }
    switch (exp.getFunction()) {
      case Empty:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Not:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Exists:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case SubsetOf: {
        checkParamTypes(exp.getFunction().toCode(), paramTypes, focus);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case SupersetOf: {
        checkParamTypes(exp.getFunction().toCode(), paramTypes, focus);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case IsDistinct:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Distinct:
        return focus;
      case Count:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer);
      case Where:
        return focus;
      case Select:
        return anything(focus.getCollectionStatus());
      case All:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Repeat:
        return anything(focus.getCollectionStatus());
      case Aggregate:
        return anything(focus.getCollectionStatus());
      case Item: {
        checkOrdered(focus, "item");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer));
        return focus;
      }
      case As: {
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, exp.getParameters().get(0).getName());
      }
      case OfType: {
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, exp.getParameters().get(0).getName());
      }
      case Type: {
        boolean s = false;
        boolean c = false;
        for (ProfiledType pt : focus.getProfiledTypes()) {
          s = s || pt.isSystemType();
          c = c || !pt.isSystemType();
        }
        if (s && c)
          return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_SimpleTypeInfo, TypeDetails.FP_ClassInfo);
        else if (s)
          return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_SimpleTypeInfo);
        else
          return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_ClassInfo);
      }
      case Is: {
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case Single:
        return focus.toSingleton();
      case First: {
        checkOrdered(focus, "first");
        return focus.toSingleton();
      }
      case Last: {
        checkOrdered(focus, "last");
        return focus.toSingleton();
      }
      case Tail: {
        checkOrdered(focus, "tail");
        return focus;
      }
      case Skip: {
        checkOrdered(focus, "skip");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer));
        return focus;
      }
      case Take: {
        checkOrdered(focus, "take");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer));
        return focus;
      }
      case Union: {
        return focus.union(paramTypes.get(0));
      }
      case Combine: {
        return focus.union(paramTypes.get(0));
      }
      case Intersect: {
        return focus.intersect(paramTypes.get(0));
      }
      case Exclude: {
        return focus;
      }
      case Iif: {
        TypeDetails types = new TypeDetails(null);
        types.update(paramTypes.get(0));
        if (paramTypes.size() > 1)
          types.update(paramTypes.get(1));
        return types;
      }
      case Lower: {
        checkContextString(focus, "lower");
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
      }
      case Upper: {
        checkContextString(focus, "upper");
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
      }
      case ToChars: {
        checkContextString(focus, "toChars");
        return new TypeDetails(CollectionStatus.ORDERED, TypeDetails.FP_String);
      }
      case Substring: {
        checkContextString(focus, "subString");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer), new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
      }
      case StartsWith: {
        checkContextString(focus, "startsWith");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case EndsWith: {
        checkContextString(focus, "endsWith");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case Matches: {
        checkContextString(focus, "matches");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case ReplaceMatches: {
        checkContextString(focus, "replaceMatches");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, "string"), new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
      }
      case Contains: {
        checkContextString(focus, "contains");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case Replace: {
        checkContextString(focus, "replace");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, "string"), new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
      }
      case Length: {
        checkContextPrimitive(focus, "length", false);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer);
      }
      case Children:
        return childTypes(focus, "*");
      case Descendants:
        return childTypes(focus, "**");
      case MemberOf: {
        checkContextCoded(focus, "memberOf");
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case Trace: {
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return focus;
      }
      case Today:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_DateTime);
      case Now:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_DateTime);
      case Resolve: {
        checkContextReference(focus, "resolve");
        return new TypeDetails(CollectionStatus.SINGLETON, "DomainResource");
      }
      case Extension: {
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return new TypeDetails(CollectionStatus.SINGLETON, "Extension");
      }
      case HasValue:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case HtmlChecks:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Alias:
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return anything(CollectionStatus.SINGLETON);
      case AliasAs:
        checkParamTypes(exp.getFunction().toCode(), paramTypes, new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String));
        return focus;
      case ToInteger: {
        checkContextPrimitive(focus, "toInteger", true);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer);
      }
      case ToDecimal: {
        checkContextPrimitive(focus, "toDecimal", true);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Decimal);
      }
      case ToString: {
        checkContextPrimitive(focus, "toString", true);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
      }
      case ToQuantity: {
        checkContextPrimitive(focus, "toQuantity", true);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Quantity);
      }
      case ToBoolean: {
        checkContextPrimitive(focus, "toBoolean", false);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case ToDateTime: {
        checkContextPrimitive(focus, "toBoolean", false);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_DateTime);
      }
      case ToTime: {
        checkContextPrimitive(focus, "toBoolean", false);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Time);
      }
      case IsString:
      case IsQuantity: {
        checkContextPrimitive(focus, exp.getFunction().toCode(), true);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case IsInteger:
      case IsDecimal:
      case IsDateTime:
      case IsTime:
      case IsBoolean: {
        checkContextPrimitive(focus, exp.getFunction().toCode(), false);
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      }
      case Custom: {
        return hostServices.checkFunction(context.appInfo, exp.getName(), paramTypes);
      }
      default:
        break;
    }
    throw new Error("not Implemented yet");
  }

  /**
   * evaluate a path and return true or false (e.g. for an invariant)
   *
   * @param base - the object against which the path is being evaluated
   * @param path - the FHIR Path statement to use
   * @return
   * @throws FHIRException
   * @
   */
  public boolean evaluateToBoolean(Resource resource, Base base, String path) throws FHIRException {
    return convertToBoolean(evaluate(null, resource, base, path));
  }

  /**
   * evaluate a path and return true or false (e.g. for an invariant)
   *
   * @param base - the object against which the path is being evaluated
   * @return
   * @throws FHIRException
   * @
   */
  public boolean evaluateToBoolean(Resource resource, Base base, ExpressionNode node) throws FHIRException {
    return convertToBoolean(evaluate(null, resource, base, node));
  }

  /**
   * evaluate a path and return true or false (e.g. for an invariant)
   *
   * @param appInfo - application context
   * @param base    - the object against which the path is being evaluated
   * @return
   * @throws FHIRException
   * @
   */
  public boolean evaluateToBoolean(Object appInfo, Base resource, Base base, ExpressionNode node) throws FHIRException {
    return convertToBoolean(evaluate(appInfo, resource, base, node));
  }

  /**
   * evaluate a path and return true or false (e.g. for an invariant)
   *
   * @param base - the object against which the path is being evaluated
   * @return
   * @throws FHIRException
   * @
   */
  public boolean evaluateToBoolean(Base resource, Base base, ExpressionNode node) throws FHIRException {
    return convertToBoolean(evaluate(null, resource, base, node));
  }

  //  procedure CheckParamCount(c : integer);
  //  begin
  //    if exp.Parameters.Count <> c then
  //      raise lexer.error('The function "'+exp.name+'" requires '+inttostr(c)+' parameters', offset);
  //  end;

  /**
   * evaluate a path and a string containing the outcome (for display)
   *
   * @param base - the object against which the path is being evaluated
   * @param path - the FHIR Path statement to use
   * @return
   * @throws FHIRException
   * @
   */
  public String evaluateToString(Base base, String path) throws FHIRException {
    return convertToString(evaluate(base, path));
  }

  public String evaluateToString(Object appInfo, Base resource, Base base, ExpressionNode node) throws FHIRException {
    return convertToString(evaluate(appInfo, resource, base, node));
  }

  private List<Base> execute(ExecutionContext context, List<Base> focus, ExpressionNode exp, boolean atEntry) throws FHIRException {
//    System.out.println("Evaluate {'"+exp.toString()+"'} on "+focus.toString());
    List<Base> work = new ArrayList<Base>();
    switch (exp.getKind()) {
      case Name:
        if (atEntry && exp.getName().equals("$this"))
          work.add(context.getThisItem());
        else if (atEntry && exp.getName().equals("$total"))
          work.addAll(context.getTotal());
        else
          for (Base item : focus) {
            List<Base> outcome = execute(context, item, exp, atEntry);
            for (Base base : outcome)
              if (base != null)
                work.add(base);
          }
        break;
      case Function:
        List<Base> work2 = evaluateFunction(context, focus, exp);
        work.addAll(work2);
        break;
      case Constant:
        Base b = resolveConstant(context, exp.getConstant());
        if (b != null)
          work.add(b);
        break;
      case Group:
        work2 = execute(context, focus, exp.getGroup(), atEntry);
        work.addAll(work2);
    }

    if (exp.getInner() != null)
      work = execute(context, work, exp.getInner(), false);

    if (exp.isProximal() && exp.getOperation() != null) {
      ExpressionNode next = exp.getOpNext();
      ExpressionNode last = exp;
      while (next != null) {
        List<Base> work2 = preOperate(work, last.getOperation());
        if (work2 != null)
          work = work2;
        else if (last.getOperation() == Operation.Is || last.getOperation() == Operation.As) {
          work2 = executeTypeName(context, focus, next, false);
          work = operate(work, last.getOperation(), work2);
        } else {
          work2 = execute(context, focus, next, true);
          work = operate(work, last.getOperation(), work2);
//          System.out.println("Result of {'"+last.toString()+" "+last.getOperation().toCode()+" "+next.toString()+"'}: "+focus.toString());
        }
        last = next;
        next = next.getOpNext();
      }
    }
//    System.out.println("Result of {'"+exp.toString()+"'}: "+work.toString());
    return work;
  }

  private List<Base> execute(ExecutionContext context, Base item, ExpressionNode exp, boolean atEntry) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    if (atEntry && Character.isUpperCase(exp.getName().charAt(0))) {// special case for start up
      if (item.isResource() && item.fhirType().equals(exp.getName()))
        result.add(item);
    } else
      getChildrenByName(item, exp.getName(), result);
    if (result.size() == 0 && atEntry && context.appInfo != null) {
      // well, we didn't get a match on the name - we'll see if the name matches a constant known by the context.
      // (if the name does match, and the user wants to get the constant value, they'll have to try harder...
      Base temp = hostServices.resolveConstant(context.appInfo, exp.getName());
      if (temp != null) {
        result.add(temp);
      }
    }
    return result;
  }

  private TypeDetails executeContextType(ExecutionTypeContext context, String name) throws PathEngineException, DefinitionException {
    if (hostServices == null)
      throw new PathEngineException("Unable to resolve context reference since no host services are provided");
    return hostServices.resolveConstantType(context.appInfo, name);
  }

  private TypeDetails executeType(ExecutionTypeContext context, TypeDetails focus, ExpressionNode exp, boolean atEntry) throws PathEngineException, DefinitionException {
    TypeDetails result = new TypeDetails(null);
    switch (exp.getKind()) {
      case Name:
        if (atEntry && exp.getName().equals("$this"))
          result.update(context.getThisItem());
        else if (atEntry && exp.getName().equals("$total"))
          result.update(anything(CollectionStatus.UNORDERED));
        else if (atEntry && focus == null)
          result.update(executeContextType(context, exp.getName()));
        else {
          for (String s : focus.getTypes()) {
            result.update(executeType(s, exp, atEntry));
          }
          if (result.hasNoTypes())
            throw new PathEngineException("The name " + exp.getName() + " is not valid for any of the possible types: " + focus.describe());
        }
        break;
      case Function:
        result.update(evaluateFunctionType(context, focus, exp));
        break;
      case Constant:
        result.update(resolveConstantType(context, exp.getConstant()));
        break;
      case Group:
        result.update(executeType(context, focus, exp.getGroup(), atEntry));
    }
    exp.setTypes(result);

    if (exp.getInner() != null) {
      result = executeType(context, result, exp.getInner(), false);
    }

    if (exp.isProximal() && exp.getOperation() != null) {
      ExpressionNode next = exp.getOpNext();
      ExpressionNode last = exp;
      while (next != null) {
        TypeDetails work;
        if (last.getOperation() == Operation.Is || last.getOperation() == Operation.As)
          work = executeTypeName(context, focus, next, atEntry);
        else
          work = executeType(context, focus, next, atEntry);
        result = operateTypes(result, last.getOperation(), work);
        last = next;
        next = next.getOpNext();
      }
      exp.setOpTypes(result);
    }
    return result;
  }

  private TypeDetails executeType(String type, ExpressionNode exp, boolean atEntry) throws PathEngineException, DefinitionException {
    if (atEntry && Character.isUpperCase(exp.getName().charAt(0)) && hashTail(type).equals(exp.getName())) // special case for start up
      return new TypeDetails(CollectionStatus.SINGLETON, type);
    TypeDetails result = new TypeDetails(null);
    getChildTypesByName(type, exp.getName(), result);
    return result;
  }

  private List<Base> executeTypeName(ExecutionContext context, List<Base> focus, ExpressionNode next, boolean atEntry) {
    List<Base> result = new ArrayList<Base>();
    result.add(new StringType(next.getName()));
    return result;
  }

  private TypeDetails executeTypeName(ExecutionTypeContext context, TypeDetails focus, ExpressionNode exp, boolean atEntry) throws PathEngineException, DefinitionException {
    return new TypeDetails(CollectionStatus.SINGLETON, exp.getName());
  }

  private StructureDefinition fetchStructureByType(ElementDefinition ed) throws DefinitionException {
    if (ed.getType().size() == 0)
      throw new DefinitionException("Error in discriminator at " + ed.getId() + ": no children, no type");
    if (ed.getType().size() > 1)
      throw new DefinitionException("Error in discriminator at " + ed.getId() + ": no children, multiple types");
    if (ed.getType().get(0).getProfile().size() > 1)
      throw new DefinitionException("Error in discriminator at " + ed.getId() + ": no children, multiple type profiles");
    if (ed.hasSlicing())
      throw new DefinitionException("Error in discriminator at " + ed.getId() + ": slicing found");
    if (ed.getType().get(0).hasProfile())
      return worker.fetchResource(StructureDefinition.class, ed.getType().get(0).getProfile().get(0).getValue());
    else
      return worker.fetchResource(StructureDefinition.class, ProfileUtilities.sdNs(ed.getType().get(0).getCode()));
  }

  public String forLog() {
    if (log.length() > 0)
      return " (" + log.toString() + ")";
    else
      return "";
  }

  private List<Base> funcAggregate(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> total = new ArrayList<Base>();
    if (exp.parameterCount() > 1)
      total = execute(context, focus, exp.getParameters().get(1), false);

    List<Base> pc = new ArrayList<Base>();
    for (Base item : focus) {
      ExecutionContext c = changeThis(context, item);
      c.total = total;
      total = execute(c, pc, exp.getParameters().get(0), true);
    }
    return total;
  }

  private List<Base> funcAlias(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> nl = execute(context, focus, exp.getParameters().get(0), true);
    String name = nl.get(0).primitiveValue();
    List<Base> res = new ArrayList<Base>();
    Base b = context.getAlias(name);
    if (b != null)
      res.add(b);
    return res;
  }

  private List<Base> funcAliasAs(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> nl = execute(context, focus, exp.getParameters().get(0), true);
    String name = nl.get(0).primitiveValue();
    context.addAlias(name, focus);
    return focus;
  }

  private List<Base> funcAll(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    if (exp.getParameters().size() == 1) {
      List<Base> result = new ArrayList<Base>();
      List<Base> pc = new ArrayList<Base>();
      boolean all = true;
      for (Base item : focus) {
        pc.clear();
        pc.add(item);
        if (!convertToBoolean(execute(changeThis(context, item), pc, exp.getParameters().get(0), true))) {
          all = false;
          break;
        }
      }
      result.add(new BooleanType(all).noExtensions());
      return result;
    } else {// (exp.getParameters().size() == 0) {
      List<Base> result = new ArrayList<Base>();
      boolean all = true;
      for (Base item : focus) {
        boolean v = false;
        if (item instanceof BooleanType) {
          v = ((BooleanType) item).booleanValue();
        } else
          v = item != null;
        if (!v) {
          all = false;
          break;
        }
      }
      result.add(new BooleanType(all).noExtensions());
      return result;
    }
  }

  private List<Base> funcAs(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    String tn = exp.getParameters().get(0).getName();
    for (Base b : focus)
      if (b.hasType(tn))
        result.add(b);
    return result;
  }

  private List<Base> funcChildren(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    for (Base b : focus)
      getChildrenByName(b, "*", result);
    return result;
  }

  private List<Base> funcCombine(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    for (Base item : focus) {
      result.add(item);
    }
    for (Base item : execute(context, focus, exp.getParameters().get(0), true)) {
      result.add(item);
    }
    return result;
  }

  private List<Base> funcContains(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    String sw = convertToString(execute(context, focus, exp.getParameters().get(0), true));

    if (focus.size() == 1 && !Utilities.noString(sw)) {
      String st = convertToString(focus.get(0));
      if (Utilities.noString(st))
        result.add(new BooleanType(false).noExtensions());
      else
        result.add(new BooleanType(st.contains(sw)).noExtensions());
    } else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcCount(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    result.add(new IntegerType(focus.size()).noExtensions());
    return result;
  }

  private List<Base> funcDescendants(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    List<Base> current = new ArrayList<Base>();
    current.addAll(focus);
    List<Base> added = new ArrayList<Base>();
    boolean more = true;
    while (more) {
      added.clear();
      for (Base item : current) {
        getChildrenByName(item, "*", added);
      }
      more = !added.isEmpty();
      result.addAll(added);
      current.clear();
      current.addAll(added);
    }
    return result;
  }

  private List<Base> funcDistinct(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    if (focus.size() <= 1)
      return focus;

    List<Base> result = new ArrayList<Base>();
    for (int i = 0; i < focus.size(); i++) {
      boolean found = false;
      for (int j = i + 1; j < focus.size(); j++) {
        if (doEquals(focus.get(j), focus.get(i))) {
          found = true;
          break;
        }
      }
      if (!found)
        result.add(focus.get(i));
    }
    return result;
  }

  private List<Base> funcEmpty(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    result.add(new BooleanType(ElementUtil.isEmpty(focus)).noExtensions());
    return result;
  }

  private List<Base> funcEndsWith(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    String sw = convertToString(execute(context, focus, exp.getParameters().get(0), true));

    if (focus.size() == 1 && !Utilities.noString(sw))
      result.add(new BooleanType(convertToString(focus.get(0)).endsWith(sw)).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcExclude(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    List<Base> other = execute(context, focus, exp.getParameters().get(0), true);

    for (Base item : focus) {
      if (!doContains(result, item) && !doContains(other, item))
        result.add(item);
    }
    return result;
  }

  private List<Base> funcExists(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    result.add(new BooleanType(!ElementUtil.isEmpty(focus)).noExtensions());
    return result;
  }

  private List<Base> funcExtension(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    List<Base> nl = execute(context, focus, exp.getParameters().get(0), true);
    String url = nl.get(0).primitiveValue();

    for (Base item : focus) {
      List<Base> ext = new ArrayList<Base>();
      getChildrenByName(item, "extension", ext);
      getChildrenByName(item, "modifierExtension", ext);
      for (Base ex : ext) {
        List<Base> vl = new ArrayList<Base>();
        getChildrenByName(ex, "url", vl);
        if (convertToString(vl).equals(url))
          result.add(ex);
      }
    }
    return result;
  }

  private List<Base> funcFirst(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() > 0)
      result.add(focus.get(0));
    return result;
  }

  private List<Base> funcHasValue(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() == 1) {
      String s = convertToString(focus.get(0));
      result.add(new BooleanType(!Utilities.noString(s)).noExtensions());
    }
    return result;
  }

  private List<Base> funcHtmlChecks(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    // todo: actually check the HTML
    return makeBoolean(true);
  }

  private List<Base> funcIif(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> n1 = execute(context, focus, exp.getParameters().get(0), true);
    Boolean v = convertToBoolean(n1);

    if (v)
      return execute(context, focus, exp.getParameters().get(1), true);
    else if (exp.getParameters().size() < 3)
      return new ArrayList<Base>();
    else
      return execute(context, focus, exp.getParameters().get(2), true);
  }

  private List<Base> funcIntersect(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    List<Base> other = execute(context, focus, exp.getParameters().get(0), true);

    for (Base item : focus) {
      if (!doContains(result, item) && doContains(other, item))
        result.add(item);
    }
    return result;
  }

  private List<Base> funcIs(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws PathEngineException {
    if (focus.size() == 0 || focus.size() > 1)
      return makeBoolean(false);
    String ns = null;
    String n = null;

    ExpressionNode texp = exp.getParameters().get(0);
    if (texp.getKind() != Kind.Name)
      throw new PathEngineException("Unsupported Expression type for Parameter on Is");
    if (texp.getInner() != null) {
      if (texp.getInner().getKind() != Kind.Name)
        throw new PathEngineException("Unsupported Expression type for Parameter on Is");
      ns = texp.getName();
      n = texp.getInner().getName();
    } else if (Utilities.existsInList(texp.getName(), "Boolean", "Integer", "Decimal", "String", "DateTime", "Time", "SimpleTypeInfo", "ClassInfo")) {
      ns = "System";
      n = texp.getName();
    } else {
      ns = "FHIR";
      n = texp.getName();
    }
    if (ns.equals("System")) {
      if (!(focus.get(0) instanceof Element) || ((Element) focus.get(0)).isDisallowExtensions())
        return makeBoolean(n.equals(Utilities.capitalize(focus.get(0).fhirType())));
      else
        return makeBoolean(false);
    } else if (ns.equals("FHIR")) {
      return makeBoolean(n.equals(focus.get(0).fhirType()));
    } else {
      return makeBoolean(false);
    }
  }

  private List<Base> funcIsBoolean(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() != 1)
      result.add(new BooleanType(false).noExtensions());
    else if (focus.get(0) instanceof IntegerType && ((IntegerType) focus.get(0)).getValue() >= 0)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof BooleanType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof StringType)
      result.add(new BooleanType(Utilities.existsInList(convertToString(focus.get(0)), "true", "false")).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcIsDateTime(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() != 1)
      result.add(new BooleanType(false).noExtensions());
    else if (focus.get(0) instanceof DateTimeType || focus.get(0) instanceof DateType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof StringType)
      result.add(new BooleanType((convertToString(focus.get(0)).matches
        ("([0-9]([0-9]([0-9][1-9]|[1-9]0)|[1-9]00)|[1-9]000)(-(0[1-9]|1[0-2])(-(0[1-9]|[1-2][0-9]|3[0-1])(T([01][0-9]|2[0-3]):[0-5][0-9]:([0-5][0-9]|60)(\\.[0-9]+)?(Z|(\\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?)?)?)?"))).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcIsDecimal(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() != 1)
      result.add(new BooleanType(false).noExtensions());
    else if (focus.get(0) instanceof IntegerType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof BooleanType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof DecimalType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof StringType)
      result.add(new BooleanType(Utilities.isDecimal(convertToString(focus.get(0)))).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcIsDistinct(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    if (focus.size() <= 1)
      return makeBoolean(true);

    boolean distinct = true;
    for (int i = 0; i < focus.size(); i++) {
      for (int j = i + 1; j < focus.size(); j++) {
        if (doEquals(focus.get(j), focus.get(i))) {
          distinct = false;
          break;
        }
      }
    }
    return makeBoolean(distinct);
  }

  private List<Base> funcIsInteger(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() != 1)
      result.add(new BooleanType(false).noExtensions());
    else if (focus.get(0) instanceof IntegerType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof BooleanType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof StringType)
      result.add(new BooleanType(Utilities.isInteger(convertToString(focus.get(0)))).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcIsQuantity(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() != 1)
      result.add(new BooleanType(false).noExtensions());
    else if (focus.get(0) instanceof IntegerType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof DecimalType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof Quantity)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof StringType) {
      Quantity q = parseQuantityString(focus.get(0).primitiveValue());
      result.add(new BooleanType(q != null).noExtensions());
    } else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcIsString(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() != 1)
      result.add(new BooleanType(false).noExtensions());
    else if (!(focus.get(0) instanceof DateTimeType) && !(focus.get(0) instanceof TimeType))
      result.add(new BooleanType(true).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcIsTime(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() != 1)
      result.add(new BooleanType(false).noExtensions());
    else if (focus.get(0) instanceof TimeType)
      result.add(new BooleanType(true).noExtensions());
    else if (focus.get(0) instanceof StringType)
      result.add(new BooleanType((convertToString(focus.get(0)).matches
        ("T([01][0-9]|2[0-3]):[0-5][0-9]:([0-5][0-9]|60)(\\.[0-9]+)?(Z|(\\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?"))).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcItem(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    String s = convertToString(execute(context, focus, exp.getParameters().get(0), true));
    if (Utilities.isInteger(s) && Integer.parseInt(s) < focus.size())
      result.add(focus.get(Integer.parseInt(s)));
    return result;
  }

  private List<Base> funcLast(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() > 0)
      result.add(focus.get(focus.size() - 1));
    return result;
  }

  private List<Base> funcLength(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() == 1) {
      String s = convertToString(focus.get(0));
      result.add(new IntegerType(s.length()).noExtensions());
    }
    return result;
  }

  private List<Base> funcLower(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() == 1) {
      String s = convertToString(focus.get(0));
      if (!Utilities.noString(s))
        result.add(new StringType(s.toLowerCase()).noExtensions());
    }
    return result;
  }

  private List<Base> funcMatches(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    String sw = convertToString(execute(context, focus, exp.getParameters().get(0), true));

    if (focus.size() == 1 && !Utilities.noString(sw)) {
      String st = convertToString(focus.get(0));
      if (Utilities.noString(st))
        result.add(new BooleanType(false).noExtensions());
      else
        result.add(new BooleanType(st.matches(sw)).noExtensions());
    } else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcMemberOf(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    throw new Error("not Implemented yet");
  }

  private List<Base> funcNot(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    return makeBoolean(!convertToBoolean(focus));
  }

  private List<Base> funcNow(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    result.add(DateTimeType.now());
    return result;
  }

  private List<Base> funcRepeat(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    List<Base> current = new ArrayList<Base>();
    current.addAll(focus);
    List<Base> added = new ArrayList<Base>();
    boolean more = true;
    while (more) {
      added.clear();
      List<Base> pc = new ArrayList<Base>();
      for (Base item : current) {
        pc.clear();
        pc.add(item);
        added.addAll(execute(changeThis(context, item), pc, exp.getParameters().get(0), false));
      }
      more = !added.isEmpty();
      result.addAll(added);
      current.clear();
      current.addAll(added);
    }
    return result;
  }

  private List<Base> funcReplace(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException, PathEngineException {
    List<Base> result = new ArrayList<Base>();

    if (focus.size() == 1) {
      String f = convertToString(focus.get(0));

      if (!Utilities.noString(f)) {

        if (exp.getParameters().size() != 2) {

          String t = convertToString(execute(context, focus, exp.getParameters().get(0), true));
          String r = convertToString(execute(context, focus, exp.getParameters().get(1), true));

          String n = f.replace(t, r);
          result.add(new StringType(n));
        } else {
          throw new PathEngineException(String.format("funcReplace() : checking for 2 arguments (pattern, substitution) but found %d items", exp.getParameters().size()));
        }
      } else {
        throw new PathEngineException(String.format("funcReplace() : checking for 1 string item but found empty item"));
      }
    } else {
      throw new PathEngineException(String.format("funcReplace() : checking for 1 string item but found %d items", focus.size()));
    }
    return result;
  }

  private List<Base> funcReplaceMatches(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    String sw = convertToString(execute(context, focus, exp.getParameters().get(0), true));

    if (focus.size() == 1 && !Utilities.noString(sw))
      result.add(new BooleanType(convertToString(focus.get(0)).contains(sw)).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcResolve(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    for (Base item : focus) {
      String s = convertToString(item);
      if (item.fhirType().equals("Reference")) {
        Property p = item.getChildByName("reference");
        if (p != null && p.hasValues())
          s = convertToString(p.getValues().get(0));
        else
          s = null; // a reference without any valid actual reference (just identifier or display, but we can't resolve it)
      }
      if (item.fhirType().equals("canonical")) {
        s = item.primitiveValue();
      }
      if (s != null) {
        Base res = null;
        if (s.startsWith("#")) {
          Property p = context.resource.getChildByName("contained");
          for (Base c : p.getValues()) {
            if (s.equals(c.getIdBase())) {
              res = c;
              break;
            }
          }
        } else if (hostServices != null) {
          res = hostServices.resolveReference(context.appInfo, s);
        }
        if (res != null)
          result.add(res);
      }
    }

    return result;
  }

  private List<Base> funcSelect(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    List<Base> pc = new ArrayList<Base>();
    for (Base item : focus) {
      pc.clear();
      pc.add(item);
      result.addAll(execute(changeThis(context, item), pc, exp.getParameters().get(0), true));
    }
    return result;
  }

  private List<Base> funcSingle(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws PathEngineException {
    if (focus.size() == 1)
      return focus;
    throw new PathEngineException(String.format("Single() : checking for 1 item but found %d items", focus.size()));
  }

  private List<Base> funcSkip(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> n1 = execute(context, focus, exp.getParameters().get(0), true);
    int i1 = Integer.parseInt(n1.get(0).primitiveValue());

    List<Base> result = new ArrayList<Base>();
    for (int i = i1; i < focus.size(); i++)
      result.add(focus.get(i));
    return result;
  }

  private List<Base> funcStartsWith(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    String sw = convertToString(execute(context, focus, exp.getParameters().get(0), true));

    if (focus.size() == 1 && !Utilities.noString(sw))
      result.add(new BooleanType(convertToString(focus.get(0)).startsWith(sw)).noExtensions());
    else
      result.add(new BooleanType(false).noExtensions());
    return result;
  }

  private List<Base> funcSubsetOf(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> target = execute(context, focus, exp.getParameters().get(0), true);

    boolean valid = true;
    for (Base item : focus) {
      boolean found = false;
      for (Base t : target) {
        if (Base.compareDeep(item, t, false)) {
          found = true;
          break;
        }
      }
      if (!found) {
        valid = false;
        break;
      }
    }
    List<Base> result = new ArrayList<Base>();
    result.add(new BooleanType(valid).noExtensions());
    return result;
  }

  private List<Base> funcSubstring(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    List<Base> n1 = execute(context, focus, exp.getParameters().get(0), true);
    int i1 = Integer.parseInt(n1.get(0).primitiveValue());
    int i2 = -1;
    if (exp.parameterCount() == 2) {
      List<Base> n2 = execute(context, focus, exp.getParameters().get(1), true);
      i2 = Integer.parseInt(n2.get(0).primitiveValue());
    }

    if (focus.size() == 1) {
      String sw = convertToString(focus.get(0));
      String s;
      if (i1 < 0 || i1 >= sw.length())
        return new ArrayList<Base>();
      if (exp.parameterCount() == 2)
        s = sw.substring(i1, Math.min(sw.length(), i1 + i2));
      else
        s = sw.substring(i1);
      if (!Utilities.noString(s))
        result.add(new StringType(s).noExtensions());
    }
    return result;
  }

  private List<Base> funcSupersetOf(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> target = execute(context, focus, exp.getParameters().get(0), true);

    boolean valid = true;
    for (Base item : target) {
      boolean found = false;
      for (Base t : focus) {
        if (Base.compareDeep(item, t, false)) {
          found = true;
          break;
        }
      }
      if (!found) {
        valid = false;
        break;
      }
    }
    List<Base> result = new ArrayList<Base>();
    result.add(new BooleanType(valid).noExtensions());
    return result;
  }

  private List<Base> funcTail(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    for (int i = 1; i < focus.size(); i++)
      result.add(focus.get(i));
    return result;
  }

  private List<Base> funcTake(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> n1 = execute(context, focus, exp.getParameters().get(0), true);
    int i1 = Integer.parseInt(n1.get(0).primitiveValue());

    List<Base> result = new ArrayList<Base>();
    for (int i = 0; i < Math.min(focus.size(), i1); i++)
      result.add(focus.get(i));
    return result;
  }

  private List<Base> funcToBoolean(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() == 1) {
      if (focus.get(0) instanceof BooleanType)
        result.add(focus.get(0));
      else if (focus.get(0) instanceof IntegerType)
        result.add(new BooleanType(!focus.get(0).primitiveValue().equals("0")).noExtensions());
      else if (focus.get(0) instanceof StringType) {
        if ("true".equals(focus.get(0).primitiveValue()))
          result.add(new BooleanType(true).noExtensions());
        else if ("false".equals(focus.get(0).primitiveValue()))
          result.add(new BooleanType(false).noExtensions());
      }
    }
    return result;
  }

  private List<Base> funcToChars(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() == 1) {
      String s = convertToString(focus.get(0));
      for (char c : s.toCharArray())
        result.add(new StringType(String.valueOf(c)).noExtensions());
    }
    return result;
  }

  //    private boolean isPrimitiveType(String s) {
  //            return s.equals("boolean") || s.equals("integer") || s.equals("decimal") || s.equals("base64Binary") || s.equals("instant") || s.equals("string") || s.equals("uri") || s.equals("date") || s.equals("dateTime") || s.equals("time") || s.equals("code") || s.equals("oid") || s.equals("id") || s.equals("unsignedInt") || s.equals("positiveInt") || s.equals("markdown");
  //    }

  private List<Base> funcToDateTime(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
//  List<Base> result = new ArrayList<Base>();
//  result.add(new BooleanType(convertToBoolean(focus)));
//  return result;
    throw new NotImplementedException("funcToDateTime is not implemented");
  }

  private List<Base> funcToDecimal(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    String s = convertToString(focus);
    List<Base> result = new ArrayList<Base>();
    if (Utilities.isDecimal(s))
      result.add(new DecimalType(s).noExtensions());
    if ("true".equals(s))
      result.add(new DecimalType(1).noExtensions());
    if ("false".equals(s))
      result.add(new DecimalType(0).noExtensions());
    return result;
  }

  private List<Base> funcToInteger(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    String s = convertToString(focus);
    List<Base> result = new ArrayList<Base>();
    if (Utilities.isInteger(s))
      result.add(new IntegerType(s).noExtensions());
    else if ("true".equals(s))
      result.add(new IntegerType(1).noExtensions());
    else if ("false".equals(s))
      result.add(new IntegerType(0).noExtensions());
    return result;
  }

  private List<Base> funcToQuantity(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() == 1) {
      if (focus.get(0) instanceof Quantity)
        result.add(focus.get(0));
      else if (focus.get(0) instanceof StringType) {
        Quantity q = parseQuantityString(focus.get(0).primitiveValue());
        if (q != null)
          result.add(q.noExtensions());
      } else if (focus.get(0) instanceof IntegerType) {
        result.add(new Quantity().setValue(new BigDecimal(focus.get(0).primitiveValue())).setSystem("http://unitsofmeasure.org").setCode("1").noExtensions());
      } else if (focus.get(0) instanceof DecimalType) {
        result.add(new Quantity().setValue(new BigDecimal(focus.get(0).primitiveValue())).setSystem("http://unitsofmeasure.org").setCode("1").noExtensions());
      }
    }
    return result;
  }

  private List<Base> funcToString(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    result.add(new StringType(convertToString(focus)).noExtensions());
    return result;
  }

  private List<Base> funcToTime(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
//  List<Base> result = new ArrayList<Base>();
//  result.add(new BooleanType(convertToBoolean(focus)));
//  return result;
    throw new NotImplementedException("funcToTime is not implemented");
  }

  private List<Base> funcToday(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    result.add(new DateType(new Date(), TemporalPrecisionEnum.DAY));
    return result;
  }

  private List<Base> funcTrace(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> nl = execute(context, focus, exp.getParameters().get(0), true);
    String name = nl.get(0).primitiveValue();

    log(name, focus);
    return focus;
  }

  private List<Base> funcType(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
    List<Base> result = new ArrayList<Base>();
    for (Base item : focus)
      result.add(new ClassTypeInfo(item));
    return result;
  }

  private List<Base> funcUnion(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    for (Base item : focus) {
      if (!doContains(result, item))
        result.add(item);
    }
    for (Base item : execute(context, focus, exp.getParameters().get(0), true)) {
      if (!doContains(result, item))
        result.add(item);
    }
    return result;
  }

  private List<Base> funcUpper(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    if (focus.size() == 1) {
      String s = convertToString(focus.get(0));
      if (!Utilities.noString(s))
        result.add(new StringType(s.toUpperCase()).noExtensions());
    }
    return result;
  }

  private List<Base> funcWhere(ExecutionContext context, List<Base> focus, ExpressionNode exp) throws FHIRException {
    List<Base> result = new ArrayList<Base>();
    List<Base> pc = new ArrayList<Base>();
    for (Base item : focus) {
      pc.clear();
      pc.add(item);
      if (convertToBoolean(execute(changeThis(context, item), pc, exp.getParameters().get(0), true)))
        result.add(item);
    }
    return result;
  }

  private ExpressionNode gatherPrecedence(FHIRLexer lexer, ExpressionNode start, EnumSet<Operation> ops) {
    //    work : boolean;
    //    focus, node, group : ExpressionNode;

    assert (start.isProximal());

    // is there anything to do?
    boolean work = false;
    ExpressionNode focus = start.getOpNext();
    if (ops.contains(start.getOperation())) {
      while (focus != null && focus.getOperation() != null) {
        work = work || !ops.contains(focus.getOperation());
        focus = focus.getOpNext();
      }
    } else {
      while (focus != null && focus.getOperation() != null) {
        work = work || ops.contains(focus.getOperation());
        focus = focus.getOpNext();
      }
    }
    if (!work)
      return start;

    // entry point: tricky
    ExpressionNode group;
    if (ops.contains(start.getOperation())) {
      group = newGroup(lexer, start);
      group.setProximal(true);
      focus = start;
      start = group;
    } else {
      ExpressionNode node = start;

      focus = node.getOpNext();
      while (!ops.contains(focus.getOperation())) {
        node = focus;
        focus = focus.getOpNext();
      }
      group = newGroup(lexer, focus);
      node.setOpNext(group);
    }

    // now, at this point:
    //   group is the group we are adding to, it already has a .group property filled out.
    //   focus points at the group.group
    do {
      // run until we find the end of the sequence
      while (ops.contains(focus.getOperation()))
        focus = focus.getOpNext();
      if (focus.getOperation() != null) {
        group.setOperation(focus.getOperation());
        group.setOpNext(focus.getOpNext());
        focus.setOperation(null);
        focus.setOpNext(null);
        // now look for another sequence, and start it
        ExpressionNode node = group;
        focus = group.getOpNext();
        if (focus != null) {
          while (focus != null && !ops.contains(focus.getOperation())) {
            node = focus;
            focus = focus.getOpNext();
          }
          if (focus != null) { // && (focus.Operation in Ops) - must be true
            group = newGroup(lexer, focus);
            node.setOpNext(group);
          }
        }
      }
    }
    while (focus != null && focus.getOperation() != null);
    return start;
  }

  private void getChildTypesByName(String type, String name, TypeDetails result) throws PathEngineException, DefinitionException {
    if (Utilities.noString(type))
      throw new PathEngineException("No type provided in BuildToolPathEvaluator.getChildTypesByName");
    if (type.equals("http://hl7.org/fhir/StructureDefinition/xhtml"))
      return;
    if (type.equals(TypeDetails.FP_SimpleTypeInfo)) {
      getSimpleTypeChildTypesByName(name, result);
    } else if (type.equals(TypeDetails.FP_ClassInfo)) {
      getClassInfoChildTypesByName(name, result);
    } else {
      String url = null;
      if (type.contains("#")) {
        url = type.substring(0, type.indexOf("#"));
      } else {
        url = type;
      }
      String tail = "";
      StructureDefinition sd = worker.fetchResource(StructureDefinition.class, url);
      if (sd == null)
        throw new DefinitionException("Unknown type " + type); // this really is an error, because we can only get to here if the internal infrastrucgture is wrong
      List<StructureDefinition> sdl = new ArrayList<StructureDefinition>();
      ElementDefinitionMatch m = null;
      if (type.contains("#"))
        m = getElementDefinition(sd, type.substring(type.indexOf("#") + 1), false);
      if (m != null && hasDataType(m.definition)) {
        if (m.fixedType != null) {
          StructureDefinition dt = worker.fetchResource(StructureDefinition.class, ProfileUtilities.sdNs(m.fixedType));
          if (dt == null)
            throw new DefinitionException("unknown data type " + m.fixedType);
          sdl.add(dt);
        } else
          for (TypeRefComponent t : m.definition.getType()) {
            StructureDefinition dt = worker.fetchResource(StructureDefinition.class, ProfileUtilities.sdNs(t.getCode()));
            if (dt == null)
              throw new DefinitionException("unknown data type " + t.getCode());
            sdl.add(dt);
          }
      } else {
        sdl.add(sd);
        if (type.contains("#")) {
          tail = type.substring(type.indexOf("#") + 1);
          tail = tail.substring(tail.indexOf("."));
        }
      }

      for (StructureDefinition sdi : sdl) {
        String path = sdi.getSnapshot().getElement().get(0).getPath() + tail + ".";
        if (name.equals("**")) {
          assert (result.getCollectionStatus() == CollectionStatus.UNORDERED);
          for (ElementDefinition ed : sdi.getSnapshot().getElement()) {
            if (ed.getPath().startsWith(path))
              for (TypeRefComponent t : ed.getType()) {
                if (t.hasCode() && t.getCodeElement().hasValue()) {
                  String tn = null;
                  if (t.getCode().equals("Element") || t.getCode().equals("BackboneElement"))
                    tn = sdi.getType() + "#" + ed.getPath();
                  else
                    tn = t.getCode();
                  if (t.getCode().equals("Resource")) {
                    for (String rn : worker.getResourceNames()) {
                      if (!result.hasType(worker, rn)) {
                        getChildTypesByName(result.addType(rn), "**", result);
                      }
                    }
                  } else if (!result.hasType(worker, tn)) {
                    getChildTypesByName(result.addType(tn), "**", result);
                  }
                }
              }
          }
        } else if (name.equals("*")) {
          assert (result.getCollectionStatus() == CollectionStatus.UNORDERED);
          for (ElementDefinition ed : sdi.getSnapshot().getElement()) {
            if (ed.getPath().startsWith(path) && !ed.getPath().substring(path.length()).contains("."))
              for (TypeRefComponent t : ed.getType()) {
                if (t.getCode().equals("Element") || t.getCode().equals("BackboneElement"))
                  result.addType(sdi.getType() + "#" + ed.getPath());
                else if (t.getCode().equals("Resource"))
                  result.addTypes(worker.getResourceNames());
                else
                  result.addType(t.getCode());
              }
          }
        } else {
          path = sdi.getSnapshot().getElement().get(0).getPath() + tail + "." + name;

          ElementDefinitionMatch ed = getElementDefinition(sdi, path, false);
          if (ed != null) {
            if (!Utilities.noString(ed.getFixedType()))
              result.addType(ed.getFixedType());
            else
              for (TypeRefComponent t : ed.getDefinition().getType()) {
                if (Utilities.noString(t.getCode()))
                  break; // throw new PathEngineException("Illegal reference to primitive value attribute @ "+path);

                ProfiledType pt = null;
                if (t.getCode().equals("Element") || t.getCode().equals("BackboneElement"))
                  pt = new ProfiledType(sdi.getUrl() + "#" + path);
                else if (t.getCode().equals("Resource"))
                  result.addTypes(worker.getResourceNames());
                else
                  pt = new ProfiledType(t.getCode());
                if (pt != null) {
                  if (t.hasProfile())
                    pt.addProfiles(t.getProfile());
                  if (ed.getDefinition().hasBinding())
                    pt.addBinding(ed.getDefinition().getBinding());
                  result.addType(pt);
                }
              }
          }
        }
      }
    }
  }

  /**
   * Given an item, return all the children that conform to the pattern described in name
   * <p>
   * Possible patterns:
   * - a simple name (which may be the base of a name with [] e.g. value[x])
   * - a name with a type replacement e.g. valueCodeableConcept
   * - * which means all children
   * - ** which means all descendants
   *
   * @param item
   * @param name
   * @param result
   * @throws FHIRException
   */
  protected void getChildrenByName(Base item, String name, List<Base> result) throws FHIRException {
    Base[] list = item.listChildrenByName(name, false);
    if (list != null)
      for (Base v : list)
        if (v != null)
          result.add(v);
  }

  private void getClassInfoChildTypesByName(String name, TypeDetails result) {
    if (name.equals("namespace"))
      result.addType(TypeDetails.FP_String);
    if (name.equals("name"))
      result.addType(TypeDetails.FP_String);
  }

  private ElementDefinitionMatch getElementDefinition(StructureDefinition sd, String path, boolean allowTypedName) throws PathEngineException {
    for (ElementDefinition ed : sd.getSnapshot().getElement()) {
      if (ed.getPath().equals(path)) {
        if (ed.hasContentReference()) {
          return getElementDefinitionById(sd, ed.getContentReference());
        } else
          return new ElementDefinitionMatch(ed, null);
      }
      if (ed.getPath().endsWith("[x]") && path.startsWith(ed.getPath().substring(0, ed.getPath().length() - 3)) && path.length() == ed.getPath().length() - 3)
        return new ElementDefinitionMatch(ed, null);
      if (allowTypedName && ed.getPath().endsWith("[x]") && path.startsWith(ed.getPath().substring(0, ed.getPath().length() - 3)) && path.length() > ed.getPath().length() - 3) {
        String s = Utilities.uncapitalize(path.substring(ed.getPath().length() - 3));
        if (primitiveTypes.contains(s))
          return new ElementDefinitionMatch(ed, s);
        else
          return new ElementDefinitionMatch(ed, path.substring(ed.getPath().length() - 3));
      }
      if (ed.getPath().contains(".") && path.startsWith(ed.getPath() + ".") && (ed.getType().size() > 0) && !isAbstractType(ed.getType())) {
        // now we walk into the type.
        if (ed.getType().size() > 1)  // if there's more than one type, the test above would fail this
          throw new PathEngineException("Internal typing issue....");
        StructureDefinition nsd = worker.fetchResource(StructureDefinition.class, ProfileUtilities.sdNs(ed.getType().get(0).getCode()));
        if (nsd == null)
          throw new PathEngineException("Unknown type " + ed.getType().get(0).getCode());
        return getElementDefinition(nsd, nsd.getId() + path.substring(ed.getPath().length()), allowTypedName);
      }
      if (ed.hasContentReference() && path.startsWith(ed.getPath() + ".")) {
        ElementDefinitionMatch m = getElementDefinitionById(sd, ed.getContentReference());
        return getElementDefinition(sd, m.definition.getPath() + path.substring(ed.getPath().length()), allowTypedName);
      }
    }
    return null;
  }

  private ElementDefinitionMatch getElementDefinitionById(StructureDefinition sd, String ref) {
    for (ElementDefinition ed : sd.getSnapshot().getElement()) {
      if (ref.equals("#" + ed.getId()))
        return new ElementDefinitionMatch(ed, null);
    }
    return null;
  }

  public IEvaluationContext getHostServices() {
    return hostServices;
  }

  public void setHostServices(IEvaluationContext constantResolver) {
    this.hostServices = constantResolver;
  }

  private void getSimpleTypeChildTypesByName(String name, TypeDetails result) {
    if (name.equals("namespace"))
      result.addType(TypeDetails.FP_String);
    if (name.equals("name"))
      result.addType(TypeDetails.FP_String);
  }

  private boolean hasDataType(ElementDefinition ed) {
    return ed.hasType() && !(ed.getType().get(0).getCode().equals("Element") || ed.getType().get(0).getCode().equals("BackboneElement"));
  }

  public boolean hasLog() {
    return log != null && log.length() > 0;
  }

  private boolean hasType(ElementDefinition ed, String s) {
    for (TypeRefComponent t : ed.getType())
      if (s.equalsIgnoreCase(t.getCode()))
        return true;
    return false;
  }

  private String hashTail(String type) {
    return type.contains("#") ? "" : type.substring(type.lastIndexOf("/") + 1);
  }

  private boolean isAbstractType(List<TypeRefComponent> list) {
    return list.size() != 1 ? true : Utilities.existsInList(list.get(0).getCode(), "Element", "BackboneElement", "Resource", "DomainResource");
  }

  private boolean isBoolean(List<Base> list, boolean b) {
    return list.size() == 1 && list.get(0) instanceof BooleanType && ((BooleanType) list.get(0)).booleanValue() == b;
  }

  private void log(String name, List<Base> contents) {
    if (hostServices == null || !hostServices.log(name, contents)) {
      if (log.length() > 0)
        log.append("; ");
      log.append(name);
      log.append(": ");
      boolean first = true;
      for (Base b : contents) {
        if (first)
          first = false;
        else
          log.append(",");
        log.append(convertToString(b));
      }
    }
  }

  private List<Base> makeBoolean(boolean b) {
    List<Base> res = new ArrayList<Base>();
    res.add(new BooleanType(b).noExtensions());
    return res;
  }

  private ExpressionNode newGroup(FHIRLexer lexer, ExpressionNode next) {
    ExpressionNode result = new ExpressionNode(lexer.nextId());
    result.setKind(Kind.Group);
    result.setGroup(next);
    result.getGroup().setProximal(true);
    return result;
  }

  private List<Base> opAnd(List<Base> left, List<Base> right) {
    if (left.isEmpty() && right.isEmpty())
      return new ArrayList<Base>();
    else if (isBoolean(left, false) || isBoolean(right, false))
      return makeBoolean(false);
    else if (left.isEmpty() || right.isEmpty())
      return new ArrayList<Base>();
    else if (convertToBoolean(left) && convertToBoolean(right))
      return makeBoolean(true);
    else
      return makeBoolean(false);
  }

  private List<Base> opAs(List<Base> left, List<Base> right) {
    List<Base> result = new ArrayList<Base>();
    if (left.size() != 1 || right.size() != 1)
      return result;
    else {
      String tn = convertToString(right);
      if (tn.equals(left.get(0).fhirType()))
        result.add(left.get(0));
    }
    return result;
  }

  private List<Base> opConcatenate(List<Base> left, List<Base> right) {
    List<Base> result = new ArrayList<Base>();
    result.add(new StringType(convertToString(left) + convertToString((right))));
    return result;
  }

  private List<Base> opContains(List<Base> left, List<Base> right) {
    boolean ans = true;
    for (Base r : right) {
      boolean f = false;
      for (Base l : left)
        if (doEquals(l, r)) {
          f = true;
          break;
        }
      if (!f) {
        ans = false;
        break;
      }
    }
    return makeBoolean(ans);
  }

  private List<Base> opDiv(List<Base> left, List<Base> right) throws PathEngineException {
    if (left.size() == 0)
      throw new PathEngineException("Error performing div: left operand has no value");
    if (left.size() > 1)
      throw new PathEngineException("Error performing div: left operand has more than one value");
    if (!left.get(0).isPrimitive() && !(left.get(0) instanceof Quantity))
      throw new PathEngineException(String.format("Error performing div: left operand has the wrong type (%s)", left.get(0).fhirType()));
    if (right.size() == 0)
      throw new PathEngineException("Error performing div: right operand has no value");
    if (right.size() > 1)
      throw new PathEngineException("Error performing div: right operand has more than one value");
    if (!right.get(0).isPrimitive() && !(right.get(0) instanceof Quantity))
      throw new PathEngineException(String.format("Error performing div: right operand has the wrong type (%s)", right.get(0).fhirType()));

    List<Base> result = new ArrayList<Base>();
    Base l = left.get(0);
    Base r = right.get(0);

    if (l.hasType("integer") && r.hasType("integer"))
      result.add(new IntegerType(Integer.parseInt(l.primitiveValue()) / Integer.parseInt(r.primitiveValue())));
    else if (l.hasType("decimal", "integer") && r.hasType("decimal", "integer")) {
      Decimal d1;
      try {
        d1 = new Decimal(l.primitiveValue());
        Decimal d2 = new Decimal(r.primitiveValue());
        result.add(new IntegerType(d1.divInt(d2).asDecimal()));
      } catch (UcumException e) {
        throw new PathEngineException(e);
      }
    } else
      throw new PathEngineException(String.format("Error performing div: left and right operand have incompatible or illegal types (%s, %s)", left.get(0).fhirType(), right.get(0).fhirType()));
    return result;
  }

  private List<Base> opDivideBy(List<Base> left, List<Base> right) throws PathEngineException {
    if (left.size() == 0)
      throw new PathEngineException("Error performing /: left operand has no value");
    if (left.size() > 1)
      throw new PathEngineException("Error performing /: left operand has more than one value");
    if (!left.get(0).isPrimitive() && !(left.get(0) instanceof Quantity))
      throw new PathEngineException(String.format("Error performing -: left operand has the wrong type (%s)", left.get(0).fhirType()));
    if (right.size() == 0)
      throw new PathEngineException("Error performing /: right operand has no value");
    if (right.size() > 1)
      throw new PathEngineException("Error performing /: right operand has more than one value");
    if (!right.get(0).isPrimitive() && !(right.get(0) instanceof Quantity))
      throw new PathEngineException(String.format("Error performing /: right operand has the wrong type (%s)", right.get(0).fhirType()));

    List<Base> result = new ArrayList<Base>();
    Base l = left.get(0);
    Base r = right.get(0);

    if (l.hasType("integer", "decimal", "unsignedInt", "positiveInt") && r.hasType("integer", "decimal", "unsignedInt", "positiveInt")) {
      Decimal d1;
      try {
        d1 = new Decimal(l.primitiveValue());
        Decimal d2 = new Decimal(r.primitiveValue());
        result.add(new DecimalType(d1.divide(d2).asDecimal()));
      } catch (UcumException e) {
        throw new PathEngineException(e);
      }
    } else if (l instanceof Quantity && r instanceof Quantity && worker.getUcumService() != null) {
      Pair pl = qtyToPair((Quantity) l);
      Pair pr = qtyToPair((Quantity) r);
      Pair p;
      try {
        p = worker.getUcumService().multiply(pl, pr);
        result.add(pairToQty(p));
      } catch (UcumException e) {
        throw new PathEngineException(e.getMessage(), e);
      }
    } else
      throw new PathEngineException(String.format("Error performing /: left and right operand have incompatible or illegal types (%s, %s)", left.get(0).fhirType(), right.get(0).fhirType()));
    return result;
  }

  private List<Base> opEquals(List<Base> left, List<Base> right) {
    if (left.size() != right.size())
      return makeBoolean(false);

    boolean res = true;
    for (int i = 0; i < left.size(); i++) {
      if (!doEquals(left.get(i), right.get(i))) {
        res = false;
        break;
      }
    }
    return makeBoolean(res);
  }

  private List<Base> opEquivalent(List<Base> left, List<Base> right) throws PathEngineException {
    if (left.size() != right.size())
      return makeBoolean(false);

    boolean res = true;
    for (int i = 0; i < left.size(); i++) {
      boolean found = false;
      for (int j = 0; j < right.size(); j++) {
        if (doEquivalent(left.get(i), right.get(j))) {
          found = true;
          break;
        }
      }
      if (!found) {
        res = false;
        break;
      }
    }
    return makeBoolean(res);
  }

  private List<Base> opGreater(List<Base> left, List<Base> right) throws FHIRException {
    if (left.size() == 1 && right.size() == 1 && left.get(0).isPrimitive() && right.get(0).isPrimitive()) {
      Base l = left.get(0);
      Base r = right.get(0);
      if (l.hasType("string") && r.hasType("string"))
        return makeBoolean(l.primitiveValue().compareTo(r.primitiveValue()) > 0);
      else if ((l.hasType("integer", "decimal", "unsignedInt", "positiveInt")) && (r.hasType("integer", "decimal", "unsignedInt", "positiveInt")))
        return makeBoolean(new Double(l.primitiveValue()) > new Double(r.primitiveValue()));
      else if ((l.hasType("date", "dateTime", "instant")) && (r.hasType("date", "dateTime", "instant")))
        return makeBoolean(compareDateTimeElements(l, r, false) > 0);
      else if ((l.hasType("time")) && (r.hasType("time")))
        return makeBoolean(l.primitiveValue().compareTo(r.primitiveValue()) > 0);
    } else if (left.size() == 1 && right.size() == 1 && left.get(0).fhirType().equals("Quantity") && right.get(0).fhirType().equals("Quantity")) {
      List<Base> lUnit = left.get(0).listChildrenByName("unit");
      List<Base> rUnit = right.get(0).listChildrenByName("unit");
      if (Base.compareDeep(lUnit, rUnit, true)) {
        return opGreater(left.get(0).listChildrenByName("value"), right.get(0).listChildrenByName("value"));
      } else {
        if (worker.getUcumService() == null)
          return makeBoolean(false);
        else {
          List<Base> dl = new ArrayList<Base>();
          dl.add(qtyToCanonical((Quantity) left.get(0)));
          List<Base> dr = new ArrayList<Base>();
          dr.add(qtyToCanonical((Quantity) right.get(0)));
          return opGreater(dl, dr);
        }
      }
    }
    return new ArrayList<Base>();
  }

  private List<Base> opGreaterOrEqual(List<Base> left, List<Base> right) throws FHIRException {
    if (left.size() == 1 && right.size() == 1 && left.get(0).isPrimitive() && right.get(0).isPrimitive()) {
      Base l = left.get(0);
      Base r = right.get(0);
      if (l.hasType("string") && r.hasType("string"))
        return makeBoolean(l.primitiveValue().compareTo(r.primitiveValue()) >= 0);
      else if ((l.hasType("integer", "decimal", "unsignedInt", "positiveInt")) && (r.hasType("integer", "decimal", "unsignedInt", "positiveInt")))
        return makeBoolean(new Double(l.primitiveValue()) >= new Double(r.primitiveValue()));
      else if ((l.hasType("date", "dateTime", "instant")) && (r.hasType("date", "dateTime", "instant")))
        return makeBoolean(compareDateTimeElements(l, r, false) >= 0);
      else if ((l.hasType("time")) && (r.hasType("time")))
        return makeBoolean(l.primitiveValue().compareTo(r.primitiveValue()) >= 0);
    } else if (left.size() == 1 && right.size() == 1 && left.get(0).fhirType().equals("Quantity") && right.get(0).fhirType().equals("Quantity")) {
      List<Base> lUnit = left.get(0).listChildrenByName("unit");
      List<Base> rUnit = right.get(0).listChildrenByName("unit");
      if (Base.compareDeep(lUnit, rUnit, true)) {
        return opGreaterOrEqual(left.get(0).listChildrenByName("value"), right.get(0).listChildrenByName("value"));
      } else {
        if (worker.getUcumService() == null)
          return makeBoolean(false);
        else {
          List<Base> dl = new ArrayList<Base>();
          dl.add(qtyToCanonical((Quantity) left.get(0)));
          List<Base> dr = new ArrayList<Base>();
          dr.add(qtyToCanonical((Quantity) right.get(0)));
          return opGreaterOrEqual(dl, dr);
        }
      }
    }
    return new ArrayList<Base>();
  }

  private List<Base> opImplies(List<Base> left, List<Base> right) {
    if (!convertToBoolean(left))
      return makeBoolean(true);
    else if (right.size() == 0)
      return new ArrayList<Base>();
    else
      return makeBoolean(convertToBoolean(right));
  }

  private List<Base> opIn(List<Base> left, List<Base> right) throws FHIRException {
    boolean ans = true;
    for (Base l : left) {
      boolean f = false;
      for (Base r : right)
        if (doEquals(l, r)) {
          f = true;
          break;
        }
      if (!f) {
        ans = false;
        break;
      }
    }
    return makeBoolean(ans);
  }

  private List<Base> opIs(List<Base> left, List<Base> right) {
    List<Base> result = new ArrayList<Base>();
    if (left.size() != 1 || right.size() != 1)
      result.add(new BooleanType(false).noExtensions());
    else {
      String tn = convertToString(right);
      if (left.get(0) instanceof org.hl7.fhir.r4.elementmodel.Element)
        result.add(new BooleanType(left.get(0).hasType(tn)).noExtensions());
      else if ((left.get(0) instanceof Element) || ((Element) left.get(0)).isDisallowExtensions())
        result.add(new BooleanType(Utilities.capitalize(left.get(0).fhirType()).equals(tn)).noExtensions());
      else
        result.add(new BooleanType(left.get(0).hasType(tn)).noExtensions());
    }
    return result;
  }

  private List<Base> opLessOrEqual(List<Base> left, List<Base> right) throws FHIRException {
    if (left.size() == 1 && right.size() == 1 && left.get(0).isPrimitive() && right.get(0).isPrimitive()) {
      Base l = left.get(0);
      Base r = right.get(0);
      if (l.hasType("string") && r.hasType("string"))
        return makeBoolean(l.primitiveValue().compareTo(r.primitiveValue()) <= 0);
      else if ((l.hasType("integer", "decimal", "unsignedInt", "positiveInt")) && (r.hasType("integer", "decimal", "unsignedInt", "positiveInt")))
        return makeBoolean(new Double(l.primitiveValue()) <= new Double(r.primitiveValue()));
      else if ((l.hasType("date", "dateTime", "instant")) && (r.hasType("date", "dateTime", "instant")))
        return makeBoolean(compareDateTimeElements(l, r, false) <= 0);
      else if ((l.hasType("time")) && (r.hasType("time")))
        return makeBoolean(l.primitiveValue().compareTo(r.primitiveValue()) <= 0);
    } else if (left.size() == 1 && right.size() == 1 && left.get(0).fhirType().equals("Quantity") && right.get(0).fhirType().equals("Quantity")) {
      List<Base> lUnits = left.get(0).listChildrenByName("unit");
      String lunit = lUnits.size() == 1 ? lUnits.get(0).primitiveValue() : null;
      List<Base> rUnits = right.get(0).listChildrenByName("unit");
      String runit = rUnits.size() == 1 ? rUnits.get(0).primitiveValue() : null;
      if ((lunit == null && runit == null) || lunit.equals(runit)) {
        return opLessOrEqual(left.get(0).listChildrenByName("value"), right.get(0).listChildrenByName("value"));
      } else {
        if (worker.getUcumService() == null)
          return makeBoolean(false);
        else {
          List<Base> dl = new ArrayList<Base>();
          dl.add(qtyToCanonical((Quantity) left.get(0)));
          List<Base> dr = new ArrayList<Base>();
          dr.add(qtyToCanonical((Quantity) right.get(0)));
          return opLessOrEqual(dl, dr);
        }
      }
    }
    return new ArrayList<Base>();
  }

  private List<Base> opLessThen(List<Base> left, List<Base> right) throws FHIRException {
    if (left.size() == 1 && right.size() == 1 && left.get(0).isPrimitive() && right.get(0).isPrimitive()) {
      Base l = left.get(0);
      Base r = right.get(0);
      if (l.hasType("string") && r.hasType("string"))
        return makeBoolean(l.primitiveValue().compareTo(r.primitiveValue()) < 0);
      else if ((l.hasType("integer") || l.hasType("decimal")) && (r.hasType("integer") || r.hasType("decimal")))
        return makeBoolean(new Double(l.primitiveValue()) < new Double(r.primitiveValue()));
      else if ((l.hasType("date", "dateTime", "instant")) && (r.hasType("date", "dateTime", "instant")))
        return makeBoolean(compareDateTimeElements(l, r, false) < 0);
      else if ((l.hasType("time")) && (r.hasType("time")))
        return makeBoolean(l.primitiveValue().compareTo(r.primitiveValue()) < 0);
    } else if (left.size() == 1 && right.size() == 1 && left.get(0).fhirType().equals("Quantity") && right.get(0).fhirType().equals("Quantity")) {
      List<Base> lUnit = left.get(0).listChildrenByName("code");
      List<Base> rUnit = right.get(0).listChildrenByName("code");
      if (Base.compareDeep(lUnit, rUnit, true)) {
        return opLessThen(left.get(0).listChildrenByName("value"), right.get(0).listChildrenByName("value"));
      } else {
        if (worker.getUcumService() == null)
          return makeBoolean(false);
        else {
          List<Base> dl = new ArrayList<Base>();
          dl.add(qtyToCanonical((Quantity) left.get(0)));
          List<Base> dr = new ArrayList<Base>();
          dr.add(qtyToCanonical((Quantity) right.get(0)));
          return opLessThen(dl, dr);
        }
      }
    }
    return new ArrayList<Base>();
  }

  private List<Base> opMemberOf(List<Base> left, List<Base> right) throws FHIRException {
    boolean ans = false;
    ValueSet vs = worker.fetchResource(ValueSet.class, right.get(0).primitiveValue());
    if (vs != null) {
      for (Base l : left) {
        if (l.fhirType().equals("code")) {
          if (worker.validateCode(l.castToCoding(l), vs).isOk())
            ans = true;
        } else if (l.fhirType().equals("Coding")) {
          if (worker.validateCode(l.castToCoding(l), vs).isOk())
            ans = true;
        } else if (l.fhirType().equals("CodeableConcept")) {
          if (worker.validateCode(l.castToCodeableConcept(l), vs).isOk())
            ans = true;
        }
      }
    }
    return makeBoolean(ans);
  }

  private List<Base> opMinus(List<Base> left, List<Base> right) throws PathEngineException {
    if (left.size() == 0)
      throw new PathEngineException("Error performing -: left operand has no value");
    if (left.size() > 1)
      throw new PathEngineException("Error performing -: left operand has more than one value");
    if (!left.get(0).isPrimitive())
      throw new PathEngineException(String.format("Error performing -: left operand has the wrong type (%s)", left.get(0).fhirType()));
    if (right.size() == 0)
      throw new PathEngineException("Error performing -: right operand has no value");
    if (right.size() > 1)
      throw new PathEngineException("Error performing -: right operand has more than one value");
    if (!right.get(0).isPrimitive())
      throw new PathEngineException(String.format("Error performing -: right operand has the wrong type (%s)", right.get(0).fhirType()));

    List<Base> result = new ArrayList<Base>();
    Base l = left.get(0);
    Base r = right.get(0);

    if (l.hasType("integer") && r.hasType("integer"))
      result.add(new IntegerType(Integer.parseInt(l.primitiveValue()) - Integer.parseInt(r.primitiveValue())));
    else if (l.hasType("decimal", "integer") && r.hasType("decimal", "integer"))
      result.add(new DecimalType(new BigDecimal(l.primitiveValue()).subtract(new BigDecimal(r.primitiveValue()))));
    else
      throw new PathEngineException(String.format("Error performing -: left and right operand have incompatible or illegal types (%s, %s)", left.get(0).fhirType(), right.get(0).fhirType()));
    return result;
  }

  private List<Base> opMod(List<Base> left, List<Base> right) throws PathEngineException {
    if (left.size() == 0)
      throw new PathEngineException("Error performing mod: left operand has no value");
    if (left.size() > 1)
      throw new PathEngineException("Error performing mod: left operand has more than one value");
    if (!left.get(0).isPrimitive())
      throw new PathEngineException(String.format("Error performing mod: left operand has the wrong type (%s)", left.get(0).fhirType()));
    if (right.size() == 0)
      throw new PathEngineException("Error performing mod: right operand has no value");
    if (right.size() > 1)
      throw new PathEngineException("Error performing mod: right operand has more than one value");
    if (!right.get(0).isPrimitive())
      throw new PathEngineException(String.format("Error performing mod: right operand has the wrong type (%s)", right.get(0).fhirType()));

    List<Base> result = new ArrayList<Base>();
    Base l = left.get(0);
    Base r = right.get(0);

    if (l.hasType("integer") && r.hasType("integer"))
      result.add(new IntegerType(Integer.parseInt(l.primitiveValue()) % Integer.parseInt(r.primitiveValue())));
    else if (l.hasType("decimal", "integer") && r.hasType("decimal", "integer")) {
      Decimal d1;
      try {
        d1 = new Decimal(l.primitiveValue());
        Decimal d2 = new Decimal(r.primitiveValue());
        result.add(new DecimalType(d1.modulo(d2).asDecimal()));
      } catch (UcumException e) {
        throw new PathEngineException(e);
      }
    } else
      throw new PathEngineException(String.format("Error performing mod: left and right operand have incompatible or illegal types (%s, %s)", left.get(0).fhirType(), right.get(0).fhirType()));
    return result;
  }

  private List<Base> opNotEquals(List<Base> left, List<Base> right) {
    if (left.size() != right.size())
      return makeBoolean(true);

    boolean res = true;
    for (int i = 0; i < left.size(); i++) {
      if (!doEquals(left.get(i), right.get(i))) {
        res = false;
        break;
      }
    }
    return makeBoolean(!res);
  }

  private List<Base> opNotEquivalent(List<Base> left, List<Base> right) throws PathEngineException {
    if (left.size() != right.size())
      return makeBoolean(true);

    boolean res = true;
    for (int i = 0; i < left.size(); i++) {
      boolean found = false;
      for (int j = 0; j < right.size(); j++) {
        if (doEquivalent(left.get(i), right.get(j))) {
          found = true;
          break;
        }
      }
      if (!found) {
        res = false;
        break;
      }
    }
    return makeBoolean(!res);
  }

  private List<Base> opOr(List<Base> left, List<Base> right) {
    if (left.isEmpty() && right.isEmpty())
      return new ArrayList<Base>();
    else if (convertToBoolean(left) || convertToBoolean(right))
      return makeBoolean(true);
    else if (left.isEmpty() || right.isEmpty())
      return new ArrayList<Base>();
    else
      return makeBoolean(false);
  }

  private List<Base> opPlus(List<Base> left, List<Base> right) throws PathEngineException {
    if (left.size() == 0)
      throw new PathEngineException("Error performing +: left operand has no value");
    if (left.size() > 1)
      throw new PathEngineException("Error performing +: left operand has more than one value");
    if (!left.get(0).isPrimitive())
      throw new PathEngineException(String.format("Error performing +: left operand has the wrong type (%s)", left.get(0).fhirType()));
    if (right.size() == 0)
      throw new PathEngineException("Error performing +: right operand has no value");
    if (right.size() > 1)
      throw new PathEngineException("Error performing +: right operand has more than one value");
    if (!right.get(0).isPrimitive())
      throw new PathEngineException(String.format("Error performing +: right operand has the wrong type (%s)", right.get(0).fhirType()));

    List<Base> result = new ArrayList<Base>();
    Base l = left.get(0);
    Base r = right.get(0);
    if (l.hasType("string", "id", "code", "uri") && r.hasType("string", "id", "code", "uri"))
      result.add(new StringType(l.primitiveValue() + r.primitiveValue()));
    else if (l.hasType("integer") && r.hasType("integer"))
      result.add(new IntegerType(Integer.parseInt(l.primitiveValue()) + Integer.parseInt(r.primitiveValue())));
    else if (l.hasType("decimal", "integer") && r.hasType("decimal", "integer"))
      result.add(new DecimalType(new BigDecimal(l.primitiveValue()).add(new BigDecimal(r.primitiveValue()))));
    else
      throw new PathEngineException(String.format("Error performing +: left and right operand have incompatible or illegal types (%s, %s)", left.get(0).fhirType(), right.get(0).fhirType()));
    return result;
  }

  private List<Base> opTimes(List<Base> left, List<Base> right) throws PathEngineException {
    if (left.size() == 0)
      throw new PathEngineException("Error performing *: left operand has no value");
    if (left.size() > 1)
      throw new PathEngineException("Error performing *: left operand has more than one value");
    if (!left.get(0).isPrimitive() && !(left.get(0) instanceof Quantity))
      throw new PathEngineException(String.format("Error performing +: left operand has the wrong type (%s)", left.get(0).fhirType()));
    if (right.size() == 0)
      throw new PathEngineException("Error performing *: right operand has no value");
    if (right.size() > 1)
      throw new PathEngineException("Error performing *: right operand has more than one value");
    if (!right.get(0).isPrimitive() && !(right.get(0) instanceof Quantity))
      throw new PathEngineException(String.format("Error performing *: right operand has the wrong type (%s)", right.get(0).fhirType()));

    List<Base> result = new ArrayList<Base>();
    Base l = left.get(0);
    Base r = right.get(0);

    if (l.hasType("integer") && r.hasType("integer"))
      result.add(new IntegerType(Integer.parseInt(l.primitiveValue()) * Integer.parseInt(r.primitiveValue())));
    else if (l.hasType("decimal", "integer") && r.hasType("decimal", "integer"))
      result.add(new DecimalType(new BigDecimal(l.primitiveValue()).multiply(new BigDecimal(r.primitiveValue()))));
    else if (l instanceof Quantity && r instanceof Quantity && worker.getUcumService() != null) {
      Pair pl = qtyToPair((Quantity) l);
      Pair pr = qtyToPair((Quantity) r);
      Pair p;
      try {
        p = worker.getUcumService().multiply(pl, pr);
        result.add(pairToQty(p));
      } catch (UcumException e) {
        throw new PathEngineException(e.getMessage(), e);
      }
    } else
      throw new PathEngineException(String.format("Error performing *: left and right operand have incompatible or illegal types (%s, %s)", left.get(0).fhirType(), right.get(0).fhirType()));
    return result;
  }

  private List<Base> opUnion(List<Base> left, List<Base> right) {
    List<Base> result = new ArrayList<Base>();
    for (Base item : left) {
      if (!doContains(result, item))
        result.add(item);
    }
    for (Base item : right) {
      if (!doContains(result, item))
        result.add(item);
    }
    return result;
  }

  private List<Base> opXor(List<Base> left, List<Base> right) {
    if (left.isEmpty() || right.isEmpty())
      return new ArrayList<Base>();
    else
      return makeBoolean(convertToBoolean(left) ^ convertToBoolean(right));
  }

  private List<Base> operate(List<Base> left, Operation operation, List<Base> right) throws FHIRException {
    switch (operation) {
      case Equals:
        return opEquals(left, right);
      case Equivalent:
        return opEquivalent(left, right);
      case NotEquals:
        return opNotEquals(left, right);
      case NotEquivalent:
        return opNotEquivalent(left, right);
      case LessThen:
        return opLessThen(left, right);
      case Greater:
        return opGreater(left, right);
      case LessOrEqual:
        return opLessOrEqual(left, right);
      case GreaterOrEqual:
        return opGreaterOrEqual(left, right);
      case Union:
        return opUnion(left, right);
      case In:
        return opIn(left, right);
      case MemberOf:
        return opMemberOf(left, right);
      case Contains:
        return opContains(left, right);
      case Or:
        return opOr(left, right);
      case And:
        return opAnd(left, right);
      case Xor:
        return opXor(left, right);
      case Implies:
        return opImplies(left, right);
      case Plus:
        return opPlus(left, right);
      case Times:
        return opTimes(left, right);
      case Minus:
        return opMinus(left, right);
      case Concatenate:
        return opConcatenate(left, right);
      case DivideBy:
        return opDivideBy(left, right);
      case Div:
        return opDiv(left, right);
      case Mod:
        return opMod(left, right);
      case Is:
        return opIs(left, right);
      case As:
        return opAs(left, right);
      default:
        throw new Error("Not Done Yet: " + operation.toCode());
    }
  }

  private TypeDetails operateTypes(TypeDetails left, Operation operation, TypeDetails right) {
    switch (operation) {
      case Equals:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Equivalent:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case NotEquals:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case NotEquivalent:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case LessThen:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Greater:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case LessOrEqual:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case GreaterOrEqual:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Is:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case As:
        return new TypeDetails(CollectionStatus.SINGLETON, right.getTypes());
      case Union:
        return left.union(right);
      case Or:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case And:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Xor:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Implies:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Times:
        TypeDetails result = new TypeDetails(CollectionStatus.SINGLETON);
        if (left.hasType(worker, "integer") && right.hasType(worker, "integer"))
          result.addType(TypeDetails.FP_Integer);
        else if (left.hasType(worker, "integer", "decimal") && right.hasType(worker, "integer", "decimal"))
          result.addType(TypeDetails.FP_Decimal);
        return result;
      case DivideBy:
        result = new TypeDetails(CollectionStatus.SINGLETON);
        if (left.hasType(worker, "integer") && right.hasType(worker, "integer"))
          result.addType(TypeDetails.FP_Decimal);
        else if (left.hasType(worker, "integer", "decimal") && right.hasType(worker, "integer", "decimal"))
          result.addType(TypeDetails.FP_Decimal);
        return result;
      case Concatenate:
        result = new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
        return result;
      case Plus:
        result = new TypeDetails(CollectionStatus.SINGLETON);
        if (left.hasType(worker, "integer") && right.hasType(worker, "integer"))
          result.addType(TypeDetails.FP_Integer);
        else if (left.hasType(worker, "integer", "decimal") && right.hasType(worker, "integer", "decimal"))
          result.addType(TypeDetails.FP_Decimal);
        else if (left.hasType(worker, "string", "id", "code", "uri") && right.hasType(worker, "string", "id", "code", "uri"))
          result.addType(TypeDetails.FP_String);
        return result;
      case Minus:
        result = new TypeDetails(CollectionStatus.SINGLETON);
        if (left.hasType(worker, "integer") && right.hasType(worker, "integer"))
          result.addType(TypeDetails.FP_Integer);
        else if (left.hasType(worker, "integer", "decimal") && right.hasType(worker, "integer", "decimal"))
          result.addType(TypeDetails.FP_Decimal);
        return result;
      case Div:
      case Mod:
        result = new TypeDetails(CollectionStatus.SINGLETON);
        if (left.hasType(worker, "integer") && right.hasType(worker, "integer"))
          result.addType(TypeDetails.FP_Integer);
        else if (left.hasType(worker, "integer", "decimal") && right.hasType(worker, "integer", "decimal"))
          result.addType(TypeDetails.FP_Decimal);
        return result;
      case In:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case MemberOf:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      case Contains:
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
      default:
        return null;
    }
  }

  private ExpressionNode organisePrecedence(FHIRLexer lexer, ExpressionNode node) {
    node = gatherPrecedence(lexer, node, EnumSet.of(Operation.Times, Operation.DivideBy, Operation.Div, Operation.Mod));
    node = gatherPrecedence(lexer, node, EnumSet.of(Operation.Plus, Operation.Minus, Operation.Concatenate));
    node = gatherPrecedence(lexer, node, EnumSet.of(Operation.Union));
    node = gatherPrecedence(lexer, node, EnumSet.of(Operation.LessThen, Operation.Greater, Operation.LessOrEqual, Operation.GreaterOrEqual));
    node = gatherPrecedence(lexer, node, EnumSet.of(Operation.Is));
    node = gatherPrecedence(lexer, node, EnumSet.of(Operation.Equals, Operation.Equivalent, Operation.NotEquals, Operation.NotEquivalent));
    node = gatherPrecedence(lexer, node, EnumSet.of(Operation.And));
    node = gatherPrecedence(lexer, node, EnumSet.of(Operation.Xor, Operation.Or));
    // last: implies
    return node;
  }

  private Base pairToQty(Pair p) {
    return new Quantity().setValue(new BigDecimal(p.getValue().toString())).setSystem("http://unitsofmeasure.org").setCode(p.getCode()).noExtensions();
  }

  /**
   * Parse a path for later use using execute
   *
   * @param path
   * @return
   * @throws PathEngineException
   * @throws Exception
   */
  public ExpressionNode parse(String path) throws FHIRLexerException {
    FHIRLexer lexer = new FHIRLexer(path);
    if (lexer.done())
      throw lexer.error("Path cannot be empty");
    ExpressionNode result = parseExpression(lexer, true);
    if (!lexer.done())
      throw lexer.error("Premature ExpressionNode termination at unexpected token \"" + lexer.getCurrent() + "\"");
    result.check();
    return result;
  }

  /**
   * Parse a path that is part of some other syntax
   *
   * @return
   * @throws PathEngineException
   * @throws Exception
   */
  public ExpressionNode parse(FHIRLexer lexer) throws FHIRLexerException {
    ExpressionNode result = parseExpression(lexer, true);
    result.check();
    return result;
  }

  private ExpressionNode parseExpression(FHIRLexer lexer, boolean proximal) throws FHIRLexerException {
    ExpressionNode result = new ExpressionNode(lexer.nextId());
    SourceLocation c = lexer.getCurrentStartLocation();
    result.setStart(lexer.getCurrentLocation());
    // special:
    if (lexer.getCurrent().equals("-")) {
      lexer.take();
      lexer.setCurrent("-" + lexer.getCurrent());
    }
    if (lexer.getCurrent().equals("+")) {
      lexer.take();
      lexer.setCurrent("+" + lexer.getCurrent());
    }
    if (lexer.isConstant(false)) {
      boolean isString = lexer.isStringConstant();
      result.setConstant(processConstant(lexer));
      result.setKind(Kind.Constant);
      if (!isString && !lexer.done() && (result.getConstant() instanceof IntegerType || result.getConstant() instanceof DecimalType) && (lexer.isStringConstant() || lexer.hasToken("year", "years", "month", "months", "week", "weeks", "day", "days", "hour", "hours", "minute", "minutes", "second", "seconds", "millisecond", "milliseconds"))) {
        // it's a quantity
        String ucum = null;
        if (lexer.hasToken("year", "years", "month", "months", "week", "weeks", "day", "days", "hour", "hours", "minute", "minutes", "second", "seconds", "millisecond", "milliseconds")) {
          String s = lexer.take();
          if (s.equals("year") || s.equals("years"))
            ucum = "a";
          else if (s.equals("month") || s.equals("months"))
            ucum = "mo";
          else if (s.equals("week") || s.equals("weeks"))
            ucum = "wk";
          else if (s.equals("day") || s.equals("days"))
            ucum = "d";
          else if (s.equals("hour") || s.equals("hours"))
            ucum = "h";
          else if (s.equals("minute") || s.equals("minutes"))
            ucum = "min";
          else if (s.equals("second") || s.equals("seconds"))
            ucum = "s";
          else // (s.equals("millisecond") || s.equals("milliseconds"))
            ucum = "ms";
        } else
          ucum = lexer.readConstant("units");
        result.setConstant(new Quantity().setValue(new BigDecimal(result.getConstant().primitiveValue())).setSystem("http://unitsofmeasure.org").setCode(ucum));
      }
      result.setEnd(lexer.getCurrentLocation());
    } else if ("(".equals(lexer.getCurrent())) {
      lexer.next();
      result.setKind(Kind.Group);
      result.setGroup(parseExpression(lexer, true));
      if (!")".equals(lexer.getCurrent()))
        throw lexer.error("Found " + lexer.getCurrent() + " expecting a \")\"");
      result.setEnd(lexer.getCurrentLocation());
      lexer.next();
    } else {
      if (!lexer.isToken() && !lexer.getCurrent().startsWith("\""))
        throw lexer.error("Found " + lexer.getCurrent() + " expecting a token name");
      if (lexer.getCurrent().startsWith("\""))
        result.setName(lexer.readConstant("Path Name"));
      else
        result.setName(lexer.take());
      result.setEnd(lexer.getCurrentLocation());
      if (!result.checkName())
        throw lexer.error("Found " + result.getName() + " expecting a valid token name");
      if ("(".equals(lexer.getCurrent())) {
        Function f = Function.fromCode(result.getName());
        FunctionDetails details = null;
        if (f == null) {
          if (hostServices != null)
            details = hostServices.resolveFunction(result.getName());
          if (details == null)
            throw lexer.error("The name " + result.getName() + " is not a valid function name");
          f = Function.Custom;
        }
        result.setKind(Kind.Function);
        result.setFunction(f);
        lexer.next();
        while (!")".equals(lexer.getCurrent())) {
          result.getParameters().add(parseExpression(lexer, true));
          if (",".equals(lexer.getCurrent()))
            lexer.next();
          else if (!")".equals(lexer.getCurrent()))
            throw lexer.error("The token " + lexer.getCurrent() + " is not expected here - either a \",\" or a \")\" expected");
        }
        result.setEnd(lexer.getCurrentLocation());
        lexer.next();
        checkParameters(lexer, c, result, details);
      } else
        result.setKind(Kind.Name);
    }
    ExpressionNode focus = result;
    if ("[".equals(lexer.getCurrent())) {
      lexer.next();
      ExpressionNode item = new ExpressionNode(lexer.nextId());
      item.setKind(Kind.Function);
      item.setFunction(ExpressionNode.Function.Item);
      item.getParameters().add(parseExpression(lexer, true));
      if (!lexer.getCurrent().equals("]"))
        throw lexer.error("The token " + lexer.getCurrent() + " is not expected here - a \"]\" expected");
      lexer.next();
      result.setInner(item);
      focus = item;
    }
    if (".".equals(lexer.getCurrent())) {
      lexer.next();
      focus.setInner(parseExpression(lexer, false));
    }
    result.setProximal(proximal);
    if (proximal) {
      while (lexer.isOp()) {
        focus.setOperation(ExpressionNode.Operation.fromCode(lexer.getCurrent()));
        focus.setOpStart(lexer.getCurrentStartLocation());
        focus.setOpEnd(lexer.getCurrentLocation());
        lexer.next();
        focus.setOpNext(parseExpression(lexer, false));
        focus = focus.getOpNext();
      }
      result = organisePrecedence(lexer, result);
    }
    return result;
  }

  public Quantity parseQuantityString(String s) {
    if (s == null)
      return null;
    s = s.trim();
    if (s.contains(" ")) {
      String v = s.substring(0, s.indexOf(" ")).trim();
      s = s.substring(s.indexOf(" ")).trim();
      if (!Utilities.isDecimal(v))
        return null;
      if (s.startsWith("'") && s.endsWith("'"))
        return Quantity.fromUcum(v, s.substring(1, s.length() - 1));
      if (s.equals("year") || s.equals("years"))
        return Quantity.fromUcum(v, "a");
      else if (s.equals("month") || s.equals("months"))
        return Quantity.fromUcum(v, "mo");
      else if (s.equals("week") || s.equals("weeks"))
        return Quantity.fromUcum(v, "wk");
      else if (s.equals("day") || s.equals("days"))
        return Quantity.fromUcum(v, "d");
      else if (s.equals("hour") || s.equals("hours"))
        return Quantity.fromUcum(v, "h");
      else if (s.equals("minute") || s.equals("minutes"))
        return Quantity.fromUcum(v, "min");
      else if (s.equals("second") || s.equals("seconds"))
        return Quantity.fromUcum(v, "s");
      else if (s.equals("millisecond") || s.equals("milliseconds"))
        return Quantity.fromUcum(v, "ms");
      else
        return null;
    } else {
      if (Utilities.isDecimal(s))
        return new Quantity().setValue(new BigDecimal(s)).setSystem("http://unitsofmeasure.org").setCode("1");
      else
        return null;
    }
  }

  private List<Base> preOperate(List<Base> left, Operation operation) {
    switch (operation) {
      case And:
        return isBoolean(left, false) ? makeBoolean(false) : null;
      case Or:
        return isBoolean(left, true) ? makeBoolean(true) : null;
      case Implies:
        return convertToBoolean(left) ? null : makeBoolean(true);
      default:
        return null;
    }
  }

  private Base processConstant(FHIRLexer lexer) throws FHIRLexerException {
    if (lexer.isStringConstant()) {
      return new StringType(processConstantString(lexer.take(), lexer)).noExtensions();
    } else if (Utilities.isInteger(lexer.getCurrent())) {
      return new IntegerType(lexer.take()).noExtensions();
    } else if (Utilities.isDecimal(lexer.getCurrent())) {
      return new DecimalType(lexer.take()).noExtensions();
    } else if (Utilities.existsInList(lexer.getCurrent(), "true", "false")) {
      return new BooleanType(lexer.take()).noExtensions();
    } else if (lexer.getCurrent().equals("{}")) {
      lexer.take();
      return null;
    } else if (lexer.getCurrent().startsWith("%") || lexer.getCurrent().startsWith("@")) {
      return new FHIRConstant(lexer.take());
    } else
      throw lexer.error("Invalid Constant " + lexer.getCurrent());
  }

  private String processConstantString(String s, FHIRLexer lexer) throws FHIRLexerException {
    StringBuilder b = new StringBuilder();
    int i = 1;
    while (i < s.length() - 1) {
      char ch = s.charAt(i);
      if (ch == '\\') {
        i++;
        switch (s.charAt(i)) {
          case 't':
            b.append('\t');
            break;
          case 'r':
            b.append('\r');
            break;
          case 'n':
            b.append('\n');
            break;
          case 'f':
            b.append('\f');
            break;
          case '\'':
            b.append('\'');
            break;
          case '"':
            b.append('"');
            break;
          case '\\':
            b.append('\\');
            break;
          case '/':
            b.append('/');
            break;
          case 'u':
            i++;
            int uc = Integer.parseInt(s.substring(i, i + 4), 16);
            b.append((char) uc);
            i = i + 3;
            break;
          default:
            throw lexer.error("Unknown character escape \\" + s.charAt(i));
        }
        i++;
      } else {
        b.append(ch);
        i++;
      }
    }
    return b.toString();
  }

  private Base processDateConstant(Object appInfo, String value) throws PathEngineException {
    if (value.startsWith("T"))
      return new TimeType(value.substring(1)).noExtensions();
    String v = value;
    if (v.length() > 10) {
      int i = v.substring(10).indexOf("-");
      if (i == -1)
        i = v.substring(10).indexOf("+");
      if (i == -1)
        i = v.substring(10).indexOf("Z");
      v = i == -1 ? value : v.substring(0, 10 + i);
    }
    if (v.length() > 10)
      return new DateTimeType(value).noExtensions();
    else
      return new DateType(value).noExtensions();
  }

  private boolean qtyEqual(Quantity left, Quantity right) {
    if (worker.getUcumService() != null) {
      DecimalType dl = qtyToCanonical(left);
      DecimalType dr = qtyToCanonical(right);
      if (dl != null && dr != null)
        return doEquals(dl, dr);
    }
    return left.equals(right);
  }

  private boolean qtyEquivalent(Quantity left, Quantity right) throws PathEngineException {
    if (worker.getUcumService() != null) {
      DecimalType dl = qtyToCanonical(left);
      DecimalType dr = qtyToCanonical(right);
      if (dl != null && dr != null)
        return doEquivalent(dl, dr);
    }
    return left.equals(right);
  }

  private DecimalType qtyToCanonical(Quantity q) {
    if (!"http://unitsofmeasure.org".equals(q.getSystem()))
      return null;
    try {
      Pair p = new Pair(new Decimal(q.getValue().toPlainString()), q.getCode());
      Pair c = worker.getUcumService().getCanonicalForm(p);
      return new DecimalType(c.getValue().asDecimal());
    } catch (UcumException e) {
      return null;
    }
  }

  private Pair qtyToPair(Quantity q) {
    if (!"http://unitsofmeasure.org".equals(q.getSystem()))
      return null;
    try {
      return new Pair(new Decimal(q.getValue().toPlainString()), q.getCode());
    } catch (UcumException e) {
      return null;
    }
  }

  private Base resolveConstant(ExecutionContext context, Base constant) throws PathEngineException {
    if (!(constant instanceof FHIRConstant))
      return constant;
    FHIRConstant c = (FHIRConstant) constant;
    if (c.getValue().startsWith("%")) {
      return resolveConstant(context, c.getValue());
    } else if (c.getValue().startsWith("@")) {
      return processDateConstant(context.appInfo, c.getValue().substring(1));
    } else
      throw new PathEngineException("Invaild FHIR Constant " + c.getValue());
  }

  private Base resolveConstant(ExecutionContext context, String s) throws PathEngineException {
    if (s.equals("%sct"))
      return new StringType("http://snomed.info/sct").noExtensions();
    else if (s.equals("%loinc"))
      return new StringType("http://loinc.org").noExtensions();
    else if (s.equals("%ucum"))
      return new StringType("http://unitsofmeasure.org").noExtensions();
    else if (s.equals("%resource")) {
      if (context.resource == null)
        throw new PathEngineException("Cannot use %resource in this context");
      return context.resource;
    } else if (s.equals("%context")) {
      return context.context;
    } else if (s.equals("%us-zip"))
      return new StringType("[0-9]{5}(-[0-9]{4}){0,1}").noExtensions();
    else if (s.startsWith("%\"vs-"))
      return new StringType("http://hl7.org/fhir/ValueSet/" + s.substring(5, s.length() - 1) + "").noExtensions();
    else if (s.startsWith("%\"cs-"))
      return new StringType("http://hl7.org/fhir/" + s.substring(5, s.length() - 1) + "").noExtensions();
    else if (s.startsWith("%\"ext-"))
      return new StringType("http://hl7.org/fhir/StructureDefinition/" + s.substring(6, s.length() - 1)).noExtensions();
    else if (hostServices == null)
      throw new PathEngineException("Unknown fixed constant '" + s + "'");
    else
      return hostServices.resolveConstant(context.appInfo, s.substring(1));
  }

  private TypeDetails resolveConstantType(ExecutionTypeContext context, Base constant) throws PathEngineException {
    if (constant instanceof BooleanType)
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Boolean);
    else if (constant instanceof IntegerType)
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Integer);
    else if (constant instanceof DecimalType)
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Decimal);
    else if (constant instanceof Quantity)
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Quantity);
    else if (constant instanceof FHIRConstant)
      return resolveConstantType(context, ((FHIRConstant) constant).getValue());
    else
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
  }

  private TypeDetails resolveConstantType(ExecutionTypeContext context, String s) throws PathEngineException {
    if (s.startsWith("@")) {
      if (s.startsWith("@T"))
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_Time);
      else
        return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_DateTime);
    } else if (s.equals("%sct"))
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
    else if (s.equals("%loinc"))
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
    else if (s.equals("%ucum"))
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
    else if (s.equals("%resource")) {
      if (context.resource == null)
        throw new PathEngineException("%resource cannot be used in this context");
      return new TypeDetails(CollectionStatus.SINGLETON, context.resource);
    } else if (s.equals("%context")) {
      return new TypeDetails(CollectionStatus.SINGLETON, context.context);
    } else if (s.equals("%map-codes"))
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
    else if (s.equals("%us-zip"))
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
    else if (s.startsWith("%\"vs-"))
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
    else if (s.startsWith("%\"cs-"))
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
    else if (s.startsWith("%\"ext-"))
      return new TypeDetails(CollectionStatus.SINGLETON, TypeDetails.FP_String);
    else if (hostServices == null)
      throw new PathEngineException("Unknown fixed constant type for '" + s + "'");
    else
      return hostServices.resolveConstantType(context.appInfo, s);
  }

  private String tailDot(String path) {
    return path.substring(path.lastIndexOf(".") + 1);
  }

  private boolean tailMatches(ElementDefinition t, String d) {
    String tail = tailDot(t.getPath());
    if (d.contains("["))
      return tail.startsWith(d.substring(0, d.indexOf('[')));
    else if (tail.equals(d))
      return true;
    else if (t.getType().size() == 1 && t.getPath().toUpperCase().endsWith(t.getType().get(0).getCode().toUpperCase()))
      return tail.startsWith(d);

    return false;
  }

  public String takeLog() {
    if (!hasLog())
      return "";
    String s = log.toString();
    log = new StringBuilder();
    return s;
  }


  // if the fhir path expressions are allowed to use constants beyond those defined in the specification
  // the application can implement them by providing a constant resolver
  public interface IEvaluationContext {
    /**
     * Check the function parameters, and throw an error if they are incorrect, or return the type for the function
     *
     * @param functionName
     * @param parameters
     * @return
     */
    public TypeDetails checkFunction(Object appContext, String functionName, List<TypeDetails> parameters) throws PathEngineException;

    /**
     * @param appContext
     * @param functionName
     * @param parameters
     * @return
     */
    public List<Base> executeFunction(Object appContext, String functionName, List<List<Base>> parameters);

    /**
     * when the .log() function is called
     *
     * @param argument
     * @param focus
     * @return
     */
    public boolean log(String argument, List<Base> focus);

    /**
     * A constant reference - e.g. a reference to a name that must be resolved in context.
     * The % will be removed from the constant name before this is invoked.
     * <p>
     * This will also be called if the host invokes the FluentPath engine with a context of null
     *
     * @param appContext - content passed into the fluent path engine
     * @param name       - name reference to resolve
     * @return the value of the reference (or null, if it's not valid, though can throw an exception if desired)
     */
    public Base resolveConstant(Object appContext, String name) throws PathEngineException;

    // extensibility for functions

    public TypeDetails resolveConstantType(Object appContext, String name) throws PathEngineException;

    /**
     * @param functionName
     * @return null if the function is not known
     */
    public FunctionDetails resolveFunction(String functionName);

    /**
     * Implementation of resolve() function. Passed a string, return matching resource, if one is known - else null
     *
     * @param url
     * @return
     * @throws FHIRException
     */
    public Base resolveReference(Object appContext, String url) throws FHIRException;

    public class FunctionDetails {
      private String description;
      private int minParameters;
      private int maxParameters;

      public FunctionDetails(String description, int minParameters, int maxParameters) {
        super();
        this.description = description;
        this.minParameters = minParameters;
        this.maxParameters = maxParameters;
      }

      public String getDescription() {
        return description;
      }

      public int getMaxParameters() {
        return maxParameters;
      }

      public int getMinParameters() {
        return minParameters;
      }

    }

  }

  private class FHIRConstant extends Base {

    private static final long serialVersionUID = -8933773658248269439L;
    private String value;

    public FHIRConstant(String value) {
      this.value = value;
    }

    @Override
    public String fhirType() {
      return "%constant";
    }

    @Override
    public String getIdBase() {
      return null;
    }

    @Override
    public void setIdBase(String value) {
    }

    public String getValue() {
      return value;
    }

    @Override
    protected void listChildren(List<Property> result) {
    }
  }

  private class ClassTypeInfo extends Base {
    private static final long serialVersionUID = 4909223114071029317L;
    private Base instance;

    public ClassTypeInfo(Base instance) {
      super();
      this.instance = instance;
    }

    @Override
    public String fhirType() {
      return "ClassInfo";
    }

    @Override
    public String getIdBase() {
      return null;
    }

    @Override
    public void setIdBase(String value) {
    }

    private String getName() {
      if ((instance instanceof Resource))
        return instance.fhirType();
      else if (!(instance instanceof Element) || ((Element) instance).isDisallowExtensions())
        return Utilities.capitalize(instance.fhirType());
      else
        return instance.fhirType();
    }

    private String getNamespace() {
      if ((instance instanceof Resource))
        return "FHIR";
      else if (!(instance instanceof Element) || ((Element) instance).isDisallowExtensions())
        return "System";
      else
        return "FHIR";
    }

    public Base[] getProperty(int hash, String name, boolean checkValid) throws FHIRException {
      if (name.equals("name"))
        return new Base[] {new StringType(getName())};
      else if (name.equals("namespace"))
        return new Base[] {new StringType(getNamespace())};
      else
        return super.getProperty(hash, name, checkValid);
    }

    @Override
    protected void listChildren(List<Property> result) {
    }
  }

  private class ExecutionContext {
    private Object appInfo;
    private Base resource;
    private Base context;
    private Base thisItem;
    private List<Base> total;
    private Map<String, Base> aliases;

    public ExecutionContext(Object appInfo, Base resource, Base context, Map<String, Base> aliases, Base thisItem) {
      this.appInfo = appInfo;
      this.context = context;
      this.resource = resource;
      this.aliases = aliases;
      this.thisItem = thisItem;
    }

    public void addAlias(String name, List<Base> focus) throws FHIRException {
      if (aliases == null)
        aliases = new HashMap<String, Base>();
      else
        aliases = new HashMap<String, Base>(aliases); // clone it, since it's going to change
      if (focus.size() > 1)
        throw new FHIRException("Attempt to alias a collection, not a singleton");
      aliases.put(name, focus.size() == 0 ? null : focus.get(0));
    }

    public Base getAlias(String name) {
      return aliases == null ? null : aliases.get(name);
    }

    public Base getResource() {
      return resource;
    }

    public Base getThisItem() {
      return thisItem;
    }

    public List<Base> getTotal() {
      return total;
    }
  }

  private class ExecutionTypeContext {
    private Object appInfo;
    private String resource;
    private String context;
    private TypeDetails thisItem;
    private TypeDetails total;


    public ExecutionTypeContext(Object appInfo, String resource, String context, TypeDetails thisItem) {
      super();
      this.appInfo = appInfo;
      this.resource = resource;
      this.context = context;
      this.thisItem = thisItem;

    }

    public String getResource() {
      return resource;
    }

    public TypeDetails getThisItem() {
      return thisItem;
    }


  }

  public class ElementDefinitionMatch {
    private ElementDefinition definition;
    private String fixedType;

    public ElementDefinitionMatch(ElementDefinition definition, String fixedType) {
      super();
      this.definition = definition;
      this.fixedType = fixedType;
    }

    public ElementDefinition getDefinition() {
      return definition;
    }

    public String getFixedType() {
      return fixedType;
    }

  }

}