package org.hl7.fhir.r5.utils;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.*;

/*
  Copyright (c) 2011+, HL7, Inc.
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without modification, 
  are permitted provided that the following conditions are met:
    
   * Redistributions of source code must retain the above copyright notice, this 
     list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above copyright notice, 
     this list of conditions and the following disclaimer in the documentation 
     and/or other materials provided with the distribution.
   * Neither the name of HL7 nor the names of its contributors may be used to 
     endorse or promote products derived from this software without specific 
     prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
  POSSIBILITY OF SUCH DAMAGE.
  
 */



import org.hl7.fhir.exceptions.FHIRException;
import org.hl7.fhir.instance.model.api.IBaseResource;
import org.hl7.fhir.r5.context.IWorkerContext;
import org.hl7.fhir.r5.model.*;
import org.hl7.fhir.r5.model.Bundle.BundleEntryComponent;
import org.hl7.fhir.r5.model.Bundle.BundleLinkComponent;
import org.hl7.fhir.r5.model.Bundle.LinkRelationTypes;
import org.hl7.fhir.utilities.Utilities;
import org.hl7.fhir.utilities.graphql.Argument;
import org.hl7.fhir.utilities.graphql.Argument.ArgumentListStatus;
import org.hl7.fhir.utilities.graphql.Directive;
import org.hl7.fhir.utilities.graphql.EGraphEngine;
import org.hl7.fhir.utilities.graphql.EGraphQLException;
import org.hl7.fhir.utilities.graphql.Field;
import org.hl7.fhir.utilities.graphql.Fragment;
import org.hl7.fhir.utilities.graphql.GraphQLResponse;
import org.hl7.fhir.utilities.graphql.IGraphQLEngine;
import org.hl7.fhir.utilities.graphql.IGraphQLStorageServices;
import org.hl7.fhir.utilities.graphql.IGraphQLStorageServices.ReferenceResolution;
import org.hl7.fhir.utilities.graphql.NameValue;
import org.hl7.fhir.utilities.graphql.NumberValue;
import org.hl7.fhir.utilities.graphql.ObjectValue;
import org.hl7.fhir.utilities.graphql.Operation;
import org.hl7.fhir.utilities.graphql.Operation.OperationType;
import org.hl7.fhir.utilities.graphql.Package;
import org.hl7.fhir.utilities.graphql.Selection;
import org.hl7.fhir.utilities.graphql.StringValue;
import org.hl7.fhir.utilities.graphql.Value;
import org.hl7.fhir.utilities.graphql.Variable;
import org.hl7.fhir.utilities.graphql.VariableValue;

public class GraphQLEngine implements IGraphQLEngine {
  
  public static class SearchEdge extends Base {

    private BundleEntryComponent be;
    private String type;
    
    SearchEdge(String type, BundleEntryComponent be) {
      this.type = type;
      this.be = be;
    }
    @Override
    public String fhirType() {
      return type;
    }

    @Override
    protected void listChildren(List<Property> result) {
      throw new Error("Not Implemented");
    }

    @Override
    public String getIdBase() {
      throw new Error("Not Implemented");
    }

    @Override
    public void setIdBase(String value) {
      throw new Error("Not Implemented");
    }

    @Override
    public Property getNamedProperty(int _hash, String _name, boolean _checkValid) throws FHIRException {
      switch (_hash) {
      case 3357091:    /*mode*/     return new Property(_name, "string",   "n/a", 0, 1, be.getSearch().hasMode() ? be.getSearch().getModeElement() : null);
      case 109264530:  /*score*/    return new Property(_name, "string",   "n/a", 0, 1, be.getSearch().hasScore() ? be.getSearch().getScoreElement() : null);
      case -341064690: /*resource*/ return new Property(_name, "resource",  "n/a", 0, 1, be.hasResource() ? be.getResource() : null);
      default: return super.getNamedProperty(_hash, _name, _checkValid);
      }
    }
  }

  public static class SearchWrapper extends Base {

    private Bundle bnd;
    private String type;
    private Map<String, String> map;

    SearchWrapper(String type, Bundle bnd) throws FHIRException {
      this.type = type;
      this.bnd = bnd;
      for (BundleLinkComponent bl : bnd.getLink()) 
        if (bl.getRelation().equals(LinkRelationTypes.SELF))
          map = parseURL(bl.getUrl());
    }

    @Override
    public String fhirType() {
      return type;
    }

    @Override
    protected void listChildren(List<Property> result) {
      throw new Error("Not Implemented");
    }

    @Override
    public String getIdBase() {
      throw new Error("Not Implemented");
    }

    @Override
    public void setIdBase(String value) {
      throw new Error("Not Implemented");
    }

    @Override
    public Property getNamedProperty(int _hash, String _name, boolean _checkValid) throws FHIRException {
      switch (_hash) {
      case 97440432:   /*first*/     return new Property(_name, "string",  "n/a", 0, 1, extractLink(_name));
      case -1273775369: /*previous*/  return new Property(_name, "string",  "n/a", 0, 1, extractLink(_name));
      case 3377907:    /*next*/      return new Property(_name, "string",  "n/a", 0, 1, extractLink(_name));
      case 3314326:    /*last*/      return new Property(_name, "string",  "n/a", 0, 1, extractLink(_name));
      case 94851343:   /*count*/     return new Property(_name, "integer", "n/a", 0, 1, bnd.getTotalElement());
      case -1019779949:/*offset*/    return new Property(_name, "integer", "n/a", 0, 1, extractParam("search-offset"));
      case 860381968:  /*pagesize*/  return new Property(_name, "integer", "n/a", 0, 1, extractParam("_count"));
      case 96356950:  /*edges*/      return new Property(_name, "edge",    "n/a", 0, Integer.MAX_VALUE, getEdges());
      default: return super.getNamedProperty(_hash, _name, _checkValid);
      }
    }

    private List<Base> getEdges() {
      List<Base> list = new ArrayList<>();
      for (BundleEntryComponent be : bnd.getEntry())
        list.add(new SearchEdge(type.substring(0, type.length() - 10) + "Edge", be));
      return list;
    }

    private Base extractParam(String name) throws FHIRException {
      return map != null ? new IntegerType(map.get(name)) : null;
    }

    private Map<String, String> parseURL(String url) throws FHIRException {
      try {
        Map<String, String> map = new HashMap<String, String>();
        String[] pairs = url.split("&");
        for (String pair : pairs) {
          int idx = pair.indexOf("=");
          String key;
          key = idx > 0 ? URLDecoder.decode(pair.substring(0, idx), "UTF-8") : pair;
          String value = idx > 0 && pair.length() > idx + 1 ? URLDecoder.decode(pair.substring(idx + 1), "UTF-8") : null;
          map.put(key, value);
        }
        return map;
      } catch (UnsupportedEncodingException e) {
        throw new FHIRException(e);
      }
    }

    private Base extractLink(String _name) throws FHIRException {
      for (BundleLinkComponent bl : bnd.getLink()) {
        if (bl.getRelation().toCode().equals(_name)) {
          Map<String, String> map = parseURL(bl.getUrl());
          return new StringType(map.get("search-id")+':'+map.get("search-offset"));
        }
      }
      return null;
    }

  }
  
  private IWorkerContext context;
  
  public GraphQLEngine(IWorkerContext context) {
    super();
    this.context = context;
  }

  /**
   *  for the host to pass context into and get back on the reference resolution interface
   */
  private Object appInfo;

  /**
   *  the focus resource - if (there instanceof one. if (there isn"t,) there instanceof no focus
   */
  private Resource focus;

  /**
   * The package that describes the graphQL to be executed, operation name, and variables
   */
  private Package graphQL;

  /**
   * where the output from executing the query instanceof going to go
   */
  private GraphQLResponse output;

  /** 
   * Application provided reference resolution services 
   */
  private IGraphQLStorageServices services;

  // internal stuff 
  private Map<String, Argument> workingVariables = new HashMap<String, Argument>();

  private FHIRPathEngine fpe;

  private ExpressionNode magicExpression;

  @Override
  public void execute() throws EGraphEngine, EGraphQLException, FHIRException {
    if (graphQL == null)
      throw new EGraphEngine("Unable to process graphql - graphql document missing");
    fpe = new FHIRPathEngine(this.context);
    magicExpression = new ExpressionNode(0);

    output = new GraphQLResponse();

    Operation op = null;
    // todo: initial conditions
    if (!Utilities.noString(graphQL.getOperationName())) {
      op = graphQL.getDocument().operation(graphQL.getOperationName());
      if (op == null)
        throw new EGraphEngine("Unable to find operation \""+graphQL.getOperationName()+"\"");
    } else if ((graphQL.getDocument().getOperations().size() == 1))
      op = graphQL.getDocument().getOperations().get(0);
    else
      throw new EGraphQLException("No operation name provided, so expected to find a single operation");

    if (op.getOperationType() == OperationType.qglotMutation)
      throw new EGraphQLException("Mutation operations are not supported (yet)");

    checkNoDirectives(op.getDirectives());
    processVariables(op);
    if (focus == null)
      processSearch(output, op.getSelectionSet(), false, "");
    else
      processObject(focus, focus, output, op.getSelectionSet(), false, "");
  }

  private boolean checkBooleanDirective(Directive dir) throws EGraphQLException {
    if (dir.getArguments().size() != 1)
      throw new EGraphQLException("Unable to process @"+dir.getName()+": expected a single argument \"if\"");
    if (!dir.getArguments().get(0).getName().equals("if"))
      throw new EGraphQLException("Unable to process @"+dir.getName()+": expected a single argument \"if\"");
    List<Value> vl = resolveValues(dir.getArguments().get(0), 1);
    return vl.get(0).toString().equals("true");
  }

  private boolean checkDirectives(List<Directive> directives) throws EGraphQLException {
    Directive skip = null;
    Directive include = null;
    for (Directive dir : directives) {
      if (dir.getName().equals("skip")) {
        if ((skip == null))
          skip = dir;
        else
          throw new EGraphQLException("Duplicate @skip directives");
      } else if (dir.getName().equals("include")) {
        if ((include == null))
          include = dir;
        else
          throw new EGraphQLException("Duplicate @include directives");
      }
      else if (!Utilities.existsInList(dir.getName(), "flatten", "first", "singleton", "slice"))
        throw new EGraphQLException("Directive \""+dir.getName()+"\" instanceof not recognised");
    }
    if ((skip != null && include != null))
      throw new EGraphQLException("Cannot mix @skip and @include directives");
    if (skip != null)
      return !checkBooleanDirective(skip);
    else if (include != null)
      return checkBooleanDirective(include);
    else
      return true;
  }

  private void checkNoDirectives(List<Directive> directives) {

  }

  private boolean targetTypeOk(List<Argument> arguments, IBaseResource dest) throws EGraphQLException {
    List<String> list = new ArrayList<String>();
    for (Argument arg : arguments) {
      if ((arg.getName().equals("type"))) {
        List<Value> vl = resolveValues(arg);
        for (Value v : vl)
          list.add(v.toString());
      }
    }
    if (list.size() == 0)
      return true;
    else
      return list.indexOf(dest.fhirType()) > -1;
  }

  private boolean hasExtensions(Base obj) {
    if (obj instanceof BackboneElement)
      return ((BackboneElement) obj).getExtension().size() > 0 || ((BackboneElement) obj).getModifierExtension().size() > 0;
      else if (obj instanceof DomainResource)
        return ((DomainResource)obj).getExtension().size() > 0 || ((DomainResource)obj).getModifierExtension().size() > 0;
        else if (obj instanceof Element)
          return ((Element)obj).getExtension().size() > 0;
          else
            return false;
  }

  private boolean passesExtensionMode(Base obj, boolean extensionMode) {
    if (!obj.isPrimitive())
      return !extensionMode;
    else if (extensionMode)
      return !Utilities.noString(obj.getIdBase()) || hasExtensions(obj);
    else
      return obj.primitiveValue() != "";
  }

  private List<Base> filter(Resource context, Property prop, String fieldName, List<Argument> arguments, List<Base> values, boolean extensionMode) throws FHIRException, EGraphQLException {
    List<Base> result = new ArrayList<Base>();
    if (values.size() > 0) {
      int count = Integer.MAX_VALUE;
      int offset = 0;
      StringBuilder fp = new StringBuilder();
      for (Argument arg : arguments) {
        List<Value> vl = resolveValues(arg);
        if ((vl.size() != 1))
          throw new EGraphQLException("Incorrect number of arguments");
        if (values.get(0).isPrimitive())
          throw new EGraphQLException("Attempt to use a filter ("+arg.getName()+") on a primtive type ("+prop.getTypeCode()+")");
        if ((arg.getName().equals("fhirpath")))
          fp.append(" and "+vl.get(0).toString());
        else if ((arg.getName().equals("_count")))
          count = Integer.valueOf(vl.get(0).toString());
        else if ((arg.getName().equals("_offset")))
          offset = Integer.valueOf(vl.get(0).toString());
        else {
          Property p = values.get(0).getNamedProperty(arg.getName());
          if (p == null)
            throw new EGraphQLException("Attempt to use an unknown filter ("+arg.getName()+") on a type ("+prop.getTypeCode()+")");
          fp.append(" and "+arg.getName()+" = '"+vl.get(0).toString()+"'");
        }
      }

      // Account for situations where the GraphQL expression selected e.g.
      // effectiveDateTime but the field contains effectivePeriod
      String propName = prop.getName();
      List<Base> newValues = new ArrayList<>(values.size());
      for (Base value : values) {
        if (propName.endsWith("[x]")) {
          String propNameShortened = propName.substring(0, propName.length() - 3);
          if (fieldName.startsWith(propNameShortened) && fieldName.length() > propNameShortened.length()) {
            if (!value.fhirType().equalsIgnoreCase(fieldName.substring(propNameShortened.length()))) {
              continue;
            }
          }
        }
        newValues.add(value);
      }

      int i = 0;
      int t = 0;
      if (fp.length() == 0)
        for (Base v : newValues) {
          if ((i >= offset) && passesExtensionMode(v, extensionMode)) {
            result.add(v);
            t++;
            if (t >= count)
              break;
          }
          i++;
        } else {
          ExpressionNode node = fpe.parse(fp.substring(5));
          for (Base v : newValues) {
            if ((i >= offset) && passesExtensionMode(v, extensionMode) && fpe.evaluateToBoolean(null, context, v, node)) {
              result.add(v);
              t++;
              if (t >= count)
                break;
            }
            i++;
          }
        }
    }
    return result;
  }

  private List<Resource> filterResources(Argument fhirpath, Bundle bnd) throws EGraphQLException, FHIRException {
    List<Resource> result = new ArrayList<Resource>();
    if (bnd.getEntry().size() > 0) {
      if ((fhirpath == null))
        for (BundleEntryComponent be : bnd.getEntry())
          result.add(be.getResource());
      else {
        FHIRPathEngine fpe = new FHIRPathEngine(context);
        ExpressionNode node = fpe.parse(getSingleValue(fhirpath));
        for (BundleEntryComponent be : bnd.getEntry())
          if (fpe.evaluateToBoolean(null, be.getResource(), be.getResource(), node))
            result.add(be.getResource());
      }
    }
    return result;
  }

  private List<Resource> filterResources(Argument fhirpath, List<IBaseResource> list) throws EGraphQLException, FHIRException {
    List<Resource> result = new ArrayList<Resource>();
    if (list.size() > 0) {
      if ((fhirpath == null))
        for (IBaseResource v : list)
          result.add((Resource) v);
      else {
        FHIRPathEngine fpe = new FHIRPathEngine(context);
        ExpressionNode node = fpe.parse(getSingleValue(fhirpath));
        for (IBaseResource v : list)
          if (fpe.evaluateToBoolean(null, (Resource)v, (Base) v, node))
            result.add((Resource) v);
      }
    }
    return result;
  }

  private boolean hasArgument(List<Argument> arguments, String name, String value) {
    for (Argument arg : arguments)
      if ((arg.getName().equals(name)) && arg.hasValue(value))
        return true;
    return false;
  }

  private void processValues(Resource context, Selection sel, Property prop, ObjectValue target, List<Base> values, boolean extensionMode, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    boolean il = false;
    Argument arg = null;
    ExpressionNode expression = null;
    if (sel.getField().hasDirective("slice")) {
      Directive dir = sel.getField().directive("slice");
      String s = ((StringValue) dir.getArguments().get(0).getValues().get(0)).getValue();
      if (s.equals("$index"))
        expression = magicExpression;
      else
        expression = fpe.parse(s);
    }
    if (sel.getField().hasDirective("flatten")) // special: instruction to drop this node...
      il = prop.isList() && !sel.getField().hasDirective("first");
    else if (sel.getField().hasDirective("first")) {
      if (expression != null) 
        throw new FHIRException("You cannot mix @slice and @first");
      arg = target.addField(sel.getField().getAlias()+suffix, listStatus(sel.getField(), inheritedList));
    } else if (expression == null)
      arg = target.addField(sel.getField().getAlias()+suffix, listStatus(sel.getField(), prop.isList() || inheritedList));

    
    int index = 0;
    for (Base value : values) {
      String ss = "";
      if (expression != null) {
        if (expression == magicExpression)
          ss = suffix+'.'+Integer.toString(index);
        else
          ss = suffix+'.'+fpe.evaluateToString(null, null, null, value, expression);
        if (!sel.getField().hasDirective("flatten"))
          arg = target.addField(sel.getField().getAlias()+suffix, listStatus(sel.getField(), prop.isList() || inheritedList));
      }

      if (value.isPrimitive() && !extensionMode) {
        if (!sel.getField().getSelectionSet().isEmpty())
          throw new EGraphQLException("Encountered a selection set on a scalar field type");
        processPrimitive(arg, value);
      } else {
        if (sel.getField().getSelectionSet().isEmpty())
          throw new EGraphQLException("No Fields selected on a complex object");
        if (arg == null)
          processObject(context, value, target, sel.getField().getSelectionSet(), il, ss);
        else {
          ObjectValue n = new ObjectValue();
          arg.addValue(n);
          processObject(context, value, n, sel.getField().getSelectionSet(), il, ss);
        }
      }
      if (sel.getField().hasDirective("first"))
        return;
      index++;
    }
  }

  private void processVariables(Operation op) throws EGraphQLException {
    for (Variable varRef : op.getVariables()) {
      Argument varDef = null;
      for (Argument v : graphQL.getVariables()) 
        if (v.getName().equals(varRef.getName()))
          varDef = v;
      if (varDef != null)
        workingVariables.put(varRef.getName(), varDef); // todo: check type?
      else if (varRef.getDefaultValue() != null)
        workingVariables.put(varRef.getName(), new Argument(varRef.getName(), varRef.getDefaultValue()));
      else
        throw new EGraphQLException("No value found for variable ");
    }
  }

  private boolean isPrimitive(String typename) {
    return Utilities.existsInList(typename, "boolean", "integer", "string", "decimal", "uri", "base64Binary", "instant", "date", "dateTime", "time", "code", "oid", "id", "markdown", "unsignedInt", "positiveInt", "url", "canonical");
  }

  private boolean isResourceName(String name, String suffix) {
    if (!name.endsWith(suffix))
      return false;
    name = name.substring(0, name.length()-suffix.length());
    return context.getResourceNamesAsSet().contains(name);
  }

  private void processObject(Resource context, Base source, ObjectValue target, List<Selection> selection, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    for (Selection sel : selection) {
      if (sel.getField() != null) {
        if (checkDirectives(sel.getField().getDirectives())) {
          Property prop = source.getNamedProperty(sel.getField().getName());
          if ((prop == null) && sel.getField().getName().startsWith("_"))
            prop = source.getNamedProperty(sel.getField().getName().substring(1));
          if (prop == null) {
            if ((sel.getField().getName().equals("resourceType") && source instanceof Resource))
              target.addField("resourceType", listStatus(sel.getField(), false)).addValue(new StringValue(source.fhirType()));
            else if ((sel.getField().getName().equals("resource") && source.fhirType().equals("Reference")))
              processReference(context, source, sel.getField(), target, inheritedList, suffix);
            else if ((sel.getField().getName().equals("resource") && source.fhirType().equals("canonical")))
              processCanonicalReference(context, source, sel.getField(), target, inheritedList, suffix);
            else if (isResourceName(sel.getField().getName(), "List") && (source instanceof Resource))
              processReverseReferenceList((Resource) source, sel.getField(), target, inheritedList, suffix);
            else if (isResourceName(sel.getField().getName(), "Connection") && (source instanceof Resource))
              processReverseReferenceSearch((Resource) source, sel.getField(), target, inheritedList, suffix);
            else
              throw new EGraphQLException("Unknown property "+sel.getField().getName()+" on "+source.fhirType());
          } else {
            if (!isPrimitive(prop.getTypeCode()) && sel.getField().getName().startsWith("_"))
              throw new EGraphQLException("Unknown property "+sel.getField().getName()+" on "+source.fhirType());

          if ("id".equals(prop.getName()) && context != null) {
            prop.getValues().set(0, new IdType(context.getIdPart()));
          }

            List<Base> vl = filter(context, prop, sel.getField().getName(), sel.getField().getArguments(), prop.getValues(), sel.getField().getName().startsWith("_"));
            if (!vl.isEmpty())
              processValues(context, sel, prop, target, vl, sel.getField().getName().startsWith("_"), inheritedList, suffix);
          }
        }
      } else if (sel.getInlineFragment() != null) {
        if (checkDirectives(sel.getInlineFragment().getDirectives())) {
          if (Utilities.noString(sel.getInlineFragment().getTypeCondition()))
            throw new EGraphQLException("Not done yet - inline fragment with no type condition"); // cause why? why instanceof it even valid?
          if (source.fhirType().equals(sel.getInlineFragment().getTypeCondition())) 
            processObject(context, source, target, sel.getInlineFragment().getSelectionSet(), inheritedList, suffix);
        }
      } else if (checkDirectives(sel.getFragmentSpread().getDirectives())) {
        Fragment fragment = graphQL.getDocument().fragment(sel.getFragmentSpread().getName());
        if (fragment == null)
          throw new EGraphQLException("Unable to resolve fragment "+sel.getFragmentSpread().getName());

        if (Utilities.noString(fragment.getTypeCondition()))
          throw new EGraphQLException("Not done yet - inline fragment with no type condition"); // cause why? why instanceof it even valid?
        if (source.fhirType().equals(fragment.getTypeCondition()))
          processObject(context, source, target, fragment.getSelectionSet(), inheritedList, suffix);
      }
    }
  }

  private void processPrimitive(Argument arg, Base value) {
    String s = value.fhirType();
    if (s.equals("integer") || s.equals("decimal") || s.equals("unsignedInt") || s.equals("positiveInt"))
      arg.addValue(new NumberValue(value.primitiveValue()));
    else if (s.equals("boolean"))
      arg.addValue(new NameValue(value.primitiveValue()));
    else
      arg.addValue(new StringValue(value.primitiveValue()));
  }

  private void processReference(Resource context, Base source, Field field, ObjectValue target, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    if (!(source instanceof Reference))
      throw new EGraphQLException("Not done yet");
    if (services == null)
      throw new EGraphQLException("Resource Referencing services not provided");

    Reference ref = (Reference) source;
    ReferenceResolution res = services.lookup(appInfo, context, ref);
    if (res != null) {
      if (targetTypeOk(field.getArguments(), res.getTarget())) {
        Argument arg = target.addField(field.getAlias() + suffix, listStatus(field, inheritedList));
        ObjectValue obj = new ObjectValue();
        arg.addValue(obj);
        processObject((Resource)res.getTargetContext(), (Base) res.getTarget(), obj, field.getSelectionSet(), inheritedList, suffix);
      }
    }
    else if (!hasArgument(field.getArguments(), "optional", "true"))
      throw new EGraphQLException("Unable to resolve reference to "+ref.getReference());
  }

  private void processCanonicalReference(Resource context, Base source, Field field, ObjectValue target, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    if (!(source instanceof CanonicalType))
      throw new EGraphQLException("Not done yet");
    if (services == null)
      throw new EGraphQLException("Resource Referencing services not provided");

    Reference ref = new Reference(source.primitiveValue());
    ReferenceResolution res = services.lookup(appInfo, context, ref);
    if (res != null) {
      if (targetTypeOk(field.getArguments(), res.getTarget())) {
        Argument arg = target.addField(field.getAlias() + suffix, listStatus(field, inheritedList));
        ObjectValue obj = new ObjectValue();
        arg.addValue(obj);
        processObject((Resource)res.getTargetContext(), (Base) res.getTarget(), obj, field.getSelectionSet(), inheritedList, suffix);
      }
    }
    else if (!hasArgument(field.getArguments(), "optional", "true"))
      throw new EGraphQLException("Unable to resolve reference to "+ref.getReference());
  }

  private ArgumentListStatus listStatus(Field field, boolean isList) {
    if (field.hasDirective("singleton"))
      return ArgumentListStatus.SINGLETON;
    else if (isList)
      return ArgumentListStatus.REPEATING;
    else
      return ArgumentListStatus.NOT_SPECIFIED;
  }

  private void processReverseReferenceList(Resource source, Field field, ObjectValue target, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    if (services == null)
      throw new EGraphQLException("Resource Referencing services not provided");
    List<IBaseResource> list = new ArrayList<>();
    List<Argument> params = new ArrayList<>();
    Argument parg = null;
    for (Argument a : field.getArguments())
      if (!(a.getName().equals("_reference")))
        params.add(a);
      else if ((parg == null))
        parg = a;
      else
        throw new EGraphQLException("Duplicate parameter _reference");
    if (parg == null)
      throw new EGraphQLException("Missing parameter _reference");
    Argument arg = new Argument();
    params.add(arg);
    arg.setName(getSingleValue(parg));
    arg.addValue(new StringValue(source.fhirType()+"/"+source.getIdPart()));
    services.listResources(appInfo, field.getName().substring(0, field.getName().length() - 4), params, list);
    arg = null;
    ObjectValue obj = null;

    List<Resource> vl = filterResources(field.argument("fhirpath"), list);
    if (!vl.isEmpty()) {
      arg = target.addField(field.getAlias()+suffix, listStatus(field, true));
      for (Resource v : vl) {
        obj = new ObjectValue();
        arg.addValue(obj);
        processObject(v, v, obj, field.getSelectionSet(), inheritedList, suffix);
      }
    }
  }
  
  private void processReverseReferenceSearch(Resource source, Field field, ObjectValue target, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    if (services == null)
      throw new EGraphQLException("Resource Referencing services not provided");
    List<Argument> params = new ArrayList<Argument>();
    Argument parg = null;
    for (Argument a : field.getArguments())
      if (!(a.getName().equals("_reference")))
        params.add(a);
      else if ((parg == null))
        parg = a;
      else
        throw new EGraphQLException("Duplicate parameter _reference");
    if (parg == null)
      throw new EGraphQLException("Missing parameter _reference");
    Argument arg = new Argument();
    params.add(arg);
    arg.setName(getSingleValue(parg));
    arg.addValue(new StringValue(source.fhirType()+"/"+source.getIdPart()));
    Bundle bnd = (Bundle) services.search(appInfo, field.getName().substring(0, field.getName().length()-10), params);
    Base bndWrapper = new SearchWrapper(field.getName(), bnd);
    arg = target.addField(field.getAlias()+suffix, listStatus(field, false));
    ObjectValue obj = new ObjectValue();
    arg.addValue(obj);
    processObject(null, bndWrapper, obj, field.getSelectionSet(), inheritedList, suffix);
  }

  private void processSearch(ObjectValue target, List<Selection> selection, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    for (Selection sel : selection) {
      if ((sel.getField() == null))
        throw new EGraphQLException("Only field selections are allowed in this context");
      checkNoDirectives(sel.getField().getDirectives());

      if ((isResourceName(sel.getField().getName(), "")))
        processSearchSingle(target, sel.getField(), inheritedList, suffix);
      else if ((isResourceName(sel.getField().getName(), "List")))
        processSearchSimple(target, sel.getField(), inheritedList, suffix);
      else if ((isResourceName(sel.getField().getName(), "Connection")))
        processSearchFull(target, sel.getField(), inheritedList, suffix);
    }
  }

  private void processSearchSingle(ObjectValue target, Field field, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    if (services == null)
      throw new EGraphQLException("Resource Referencing services not provided");
    String id = "";
    for (Argument arg : field.getArguments())
      if ((arg.getName().equals("id")))
        id = getSingleValue(arg);
      else
        throw new EGraphQLException("Unknown/invalid parameter "+arg.getName());
    if (Utilities.noString(id))
      throw new EGraphQLException("No id found");
    Resource res = (Resource) services.lookup(appInfo, field.getName(), id);
    if (res == null)
      throw new EGraphQLException("Resource "+field.getName()+"/"+id+" not found");
    Argument arg = target.addField(field.getAlias()+suffix, listStatus(field, false));
    ObjectValue obj = new ObjectValue();
    arg.addValue(obj);
    processObject(res, res, obj, field.getSelectionSet(), inheritedList, suffix);
  }

  private void processSearchSimple(ObjectValue target, Field field, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    if (services == null)
      throw new EGraphQLException("Resource Referencing services not provided");
    List<IBaseResource> list = new ArrayList<>();
    services.listResources(appInfo, field.getName().substring(0, field.getName().length() - 4), field.getArguments(), list);
    Argument arg = null;
    ObjectValue obj = null;

    List<Resource> vl = filterResources(field.argument("fhirpath"), list);
    if (!vl.isEmpty()) {
      arg = target.addField(field.getAlias()+suffix, listStatus(field, true));
      for (Resource v : vl) {
        obj = new ObjectValue();
        arg.addValue(obj);
        processObject(v, v, obj, field.getSelectionSet(), inheritedList, suffix);
      }
    }
  }
  
  private void processSearchFull(ObjectValue target, Field field, boolean inheritedList, String suffix) throws EGraphQLException, FHIRException {
    if (services == null)
      throw new EGraphQLException("Resource Referencing services not provided");
    List<Argument> params = new ArrayList<Argument>();
    Argument carg = null;
    for ( Argument arg : field.getArguments())
      if (arg.getName().equals("cursor"))
        carg = arg;
      else
        params.add(arg);
    if ((carg != null)) {
      params.clear();;
      String[] parts = getSingleValue(carg).split(":");
      params.add(new Argument("search-id", new StringValue(parts[0])));
      params.add(new Argument("search-offset", new StringValue(parts[1])));
    }

    Bundle bnd = (Bundle) services.search(appInfo, field.getName().substring(0, field.getName().length()-10), params);
    SearchWrapper bndWrapper = new SearchWrapper(field.getName(), bnd);
    Argument arg = target.addField(field.getAlias()+suffix, listStatus(field, false));
    ObjectValue obj = new ObjectValue();
    arg.addValue(obj);
    processObject(null, bndWrapper, obj, field.getSelectionSet(), inheritedList, suffix);
  }

  private String getSingleValue(Argument arg) throws EGraphQLException {
    List<Value> vl = resolveValues(arg, 1);
    if (vl.size() == 0)
      return "";
    return vl.get(0).toString();
  }

  private List<Value> resolveValues(Argument arg) throws EGraphQLException {
    return resolveValues(arg, -1, "");
  }
  
  private List<Value> resolveValues(Argument arg, int max) throws EGraphQLException {
    return resolveValues(arg, max, "");
  }
  
  private List<Value> resolveValues(Argument arg, int max, String vars) throws EGraphQLException {
    List<Value> result = new ArrayList<Value>();
    for (Value v : arg.getValues()) {
      if (! (v instanceof VariableValue))
        result.add(v);
      else {
        if (vars.contains(":"+v.toString()+":"))
          throw new EGraphQLException("Recursive reference to variable "+v.toString());
        Argument a = workingVariables.get(v.toString());
        if (a == null)
          throw new EGraphQLException("No value found for variable \""+v.toString()+"\" in \""+arg.getName()+"\"");
        List<Value> vl = resolveValues(a, -1, vars+":"+v.toString()+":");
        result.addAll(vl);
      }
    }
    if ((max != -1 && result.size() > max))
      throw new EGraphQLException("Only "+Integer.toString(max)+" values are allowed for \""+arg.getName()+"\", but "+Integer.toString(result.size())+" enoucntered");
    return result;
  }


  
  
  public Object getAppInfo() {
    return appInfo;
  }

  @Override
  public void setAppInfo(Object appInfo) {
    this.appInfo = appInfo;
  }

  public Resource getFocus() {
    return focus;
  }

  @Override
  public void setFocus(IBaseResource focus) {
    this.focus = (Resource) focus;
  }

  public Package getGraphQL() {
    return graphQL;
  }

  @Override
  public void setGraphQL(Package graphQL) {
    this.graphQL = graphQL;
  }

  @Override
  public GraphQLResponse getOutput() {
    return output;
  }

  public IGraphQLStorageServices getServices() {
    return services;
  }

  @Override
  public void setServices(IGraphQLStorageServices services) {
    this.services = services;
  }


  //
//{ GraphQLSearchWrapper }
//
//constructor GraphQLSearchWrapper.Create(bundle : Bundle);
//var
//  s : String;
//{
//  inherited Create;
//  FBundle = bundle;
//  s = bundle_List.Matches["self"];
//  FParseMap = TParseMap.create(s.Substring(s.IndexOf("?")+1));
//}
//
//destructor GraphQLSearchWrapper.Destroy;
//{
//  FParseMap.free;
//  FBundle.Free;
//  inherited;
//}
//
//function GraphQLSearchWrapper.extractLink(name: String): String;
//var
//  s : String;
//  pm : TParseMap;
//{
//  s = FBundle_List.Matches[name];
//  if (s == "")
//    result = null
//  else
//  {
//    pm = TParseMap.create(s.Substring(s.IndexOf("?")+1));
//    try
//      result = String.Create(pm.GetVar("search-id")+":"+pm.GetVar("search-offset"));
//    finally
//      pm.Free;
//    }
//  }
//}
//
//function GraphQLSearchWrapper.extractParam(name: String; int : boolean): Base;
//var
//  s : String;
//{
//  s = FParseMap.GetVar(name);
//  if (s == "")
//    result = null
//  else if (int)
//    result = Integer.Create(s)
//  else
//    result = String.Create(s);
//}
//
//function GraphQLSearchWrapper.fhirType(): String;
//{
//  result = "*Connection";
//}
//
//  // http://test.fhir.org/r4/Patient?_format==text/xhtml&search-id==77c97e03-8a6c-415f-a63d-11c80cf73f&&active==true&_sort==_id&search-offset==50&_count==50
//
//function GraphQLSearchWrapper.getPropertyValue(propName: string): Property;
//var
//  list : List<GraphQLSearchEdge>;
//  be : BundleEntry;
//{
//  if (propName == "first")
//    result = Property.Create(self, propname, "string", false, String, extractLink("first"))
//  else if (propName == "previous")
//    result = Property.Create(self, propname, "string", false, String, extractLink("previous"))
//  else if (propName == "next")
//    result = Property.Create(self, propname, "string", false, String, extractLink("next"))
//  else if (propName == "last")
//    result = Property.Create(self, propname, "string", false, String, extractLink("last"))
//  else if (propName == "count")
//    result = Property.Create(self, propname, "integer", false, String, FBundle.totalElement)
//  else if (propName == "offset")
//    result = Property.Create(self, propname, "integer", false, Integer, extractParam("search-offset", true))
//  else if (propName == "pagesize")
//    result = Property.Create(self, propname, "integer", false, Integer, extractParam("_count", true))
//  else if (propName == "edges")
//  {
//    list = ArrayList<GraphQLSearchEdge>();
//    try
//      for be in FBundle.getEntry() do
//        list.add(GraphQLSearchEdge.create(be));
//      result = Property.Create(self, propname, "integer", true, Integer, List<Base>(list));
//    finally
//      list.Free;
//    }
//  }
//  else
//    result = null;
//}
//
//private void GraphQLSearchWrapper.SetBundle(const Value: Bundle);
//{
//  FBundle.Free;
//  FBundle = Value;
//}
//
//{ GraphQLSearchEdge }
//
//constructor GraphQLSearchEdge.Create(entry: BundleEntry);
//{
//  inherited Create;
//  FEntry = entry;
//}
//
//destructor GraphQLSearchEdge.Destroy;
//{
//  FEntry.Free;
//  inherited;
//}
//
//function GraphQLSearchEdge.fhirType(): String;
//{
//  result = "*Edge";
//}
//
//function GraphQLSearchEdge.getPropertyValue(propName: string): Property;
//{
//  if (propName == "mode")
//  {
//    if (FEntry.search != null)
//      result = Property.Create(self, propname, "code", false, Enum, FEntry.search.modeElement)
//    else
//      result = Property.Create(self, propname, "code", false, Enum, Base(null));
//  }
//  else if (propName == "score")
//  {
//    if (FEntry.search != null)
//      result = Property.Create(self, propname, "decimal", false, Decimal, FEntry.search.scoreElement)
//    else
//      result = Property.Create(self, propname, "decimal", false, Decimal, Base(null));
//  }
//  else if (propName == "resource")
//    result = Property.Create(self, propname, "resource", false, Resource, FEntry.getResource())
//  else
//    result = null;
//}
//
//private void GraphQLSearchEdge.SetEntry(const Value: BundleEntry);
//{
//  FEntry.Free;
//  FEntry = value;
//}
//
}