package org.hl7.fhir.r5.conformance;

/*
  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 java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.tuple.ImmutablePair;
import org.apache.commons.lang3.tuple.Pair;
import org.hl7.fhir.r5.conformance.profile.ProfileUtilities;
import org.hl7.fhir.r5.context.IWorkerContext;
import org.hl7.fhir.r5.model.Constants;
import org.hl7.fhir.r5.model.DataType;
import org.hl7.fhir.r5.model.DomainResource;
import org.hl7.fhir.r5.model.ElementDefinition;
import org.hl7.fhir.r5.model.Enumerations;
import org.hl7.fhir.r5.model.StructureDefinition;
import org.hl7.fhir.r5.model.ValueSet;
import org.hl7.fhir.r5.terminologies.ValueSetExpander;
import org.stringtemplate.v4.ST;

public class ShExGenerator {

  public enum HTMLLinkPolicy {
    NONE, EXTERNAL, INTERNAL
  }
  public boolean doDatatypes = true;                 // add data types
  public boolean withComments = true;                // include comments
  public boolean completeModel = false;              // doing complete build (fhir.shex)


  private static String SHEX_TEMPLATE = "$header$\n\n" +
          "$shapeDefinitions$";

  // A header is a list of prefixes, a base declaration and a start node
  private static String FHIR = "http://hl7.org/fhir/";
  private static String FHIR_VS = FHIR + "ValueSet/";
  private static String HEADER_TEMPLATE =
          "PREFIX fhir: <$fhir$> \n" +
                  "PREFIX fhirvs: <$fhirvs$>\n" +
                  "PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> \n" +
                  "BASE <http://hl7.org/fhir/shape/>\n$start$";

  // Start template for single (open) entry
  private static String START_TEMPLATE = "\n\nstart=@<$id$> AND {fhir:nodeRole [fhir:treeRoot]}\n";

  // Start template for complete (closed) model
  private static String ALL_START_TEMPLATE = "\n\nstart=@<All>\n";

  private static String ALL_TEMPLATE = "\n<All> $all_entries$\n";

  private static String ALL_ENTRY_TEMPLATE = "(NOT { fhir:nodeRole [fhir:treeRoot] ; a [fhir:$id$] } OR @<$id$>)";


  // Shape Definition
  //      the shape name
  //      an optional resource declaration (type + treeRoot)
  //      the list of element declarations
  //      an optional index element (for appearances inside ordered lists)
  private static String SHAPE_DEFINITION_TEMPLATE =
          "$comment$\n<$id$> CLOSED {\n    $resourceDecl$" +
                  "\n    $elements$" +
                  "\n    fhir:index xsd:integer?                 # Relative position in a list\n}\n";

  // Resource Definition
  //      an open shape of type Resource.  Used when completeModel = false.
  private static String RESOURCE_SHAPE_TEMPLATE =
          "$comment$\n<Resource> {a .+;" +
                  "\n    $elements$" +
                  "\n    fhir:index xsd:integer?" +
                  "\n}\n";

  // If we have knowledge of all of the possible resources available to us (completeModel = true), we can build
  // a model of all possible resources.
  private static String COMPLETE_RESOURCE_TEMPLATE =
          "<Resource>  @<$resources$>" +
                  "\n\n";

  // Resource Declaration
  //      a type node
  //      an optional treeRoot declaration (identifies the entry point)
  private static String RESOURCE_DECL_TEMPLATE = "\na [fhir:$id$];$root$";

  // Root Declaration.
  private static String ROOT_TEMPLATE = "\nfhir:nodeRole [fhir:treeRoot]?;";

  // Element
  //    a predicate, type and cardinality triple
  private static String ELEMENT_TEMPLATE = "$id$$defn$$card$$comment$";
  private static int COMMENT_COL = 40;
  private static int MAX_CHARS = 35;
  private static int MIN_COMMENT_SEP = 2;

  // Inner Shape Definition
  private static String INNER_SHAPE_TEMPLATE = "($comment$\n    $defn$\n)$card$";

  // Simple Element
  //    a shape reference
  private static String SIMPLE_ELEMENT_DEFN_TEMPLATE = "@<$typ$>$vsdef$";

  // Value Set Element
  private static String VALUESET_DEFN_TEMPLATE = " AND\n\t{fhir:value @$vsn$}";

  // Fixed Value Template
  private static String FIXED_VALUE_TEMPLATE = " AND\n\t{fhir:value [\"$val$\"]}";

  // A primitive element definition
  //    the actual type reference
  private static String PRIMITIVE_ELEMENT_DEFN_TEMPLATE = "$typ$$facets$";

  // Facets
  private static String MINVALUE_TEMPLATE = " MININCLUSIVE $val$";
  private static String MAXVALUE_TEMPLATE = " MAXINCLUSIVE $val$";
  private static String MAXLENGTH_TEMPLATE = " MAXLENGTH $val$";
  private static String PATTERN_TEMPLATE = " PATTERN \"$val$\"";

  // A choice of alternative shape definitions
  //  rendered as an inner anonymous shape
  private static String ALTERNATIVE_SHAPES_TEMPLATE = "fhir:$id$$comment$\n(   $altEntries$\n)$card$";

  // A typed reference definition
  private static String REFERENCE_DEFN_TEMPLATE = "@<$ref$Reference>";

  // What we emit for an xhtml
  private static String XHTML_TYPE_TEMPLATE = "xsd:string";

  // Additional type for Coding
  private static String CONCEPT_REFERENCE_TEMPLATE = "a NONLITERAL?;";

  // Additional type for CodedConcept
  private static String CONCEPT_REFERENCES_TEMPLATE = "a NONLITERAL*;";

  // Untyped resource has the extra link entry
  private static String RESOURCE_LINK_TEMPLATE = "fhir:link IRI?;";

  // Extension template
  // No longer used -- we emit the actual definition
//  private static String EXTENSION_TEMPLATE = "<Extension> {fhir:extension @<Extension>*;" +
//          "\n    fhir:index xsd:integer?" +
//          "\n}\n";

  // A typed reference -- a fhir:uri with an optional type and the possibility of a resolvable shape
  private static String TYPED_REFERENCE_TEMPLATE = "\n<$refType$Reference> CLOSED {" +
          "\n    fhir:Element.id @<id>?;" +
          "\n    fhir:Element.extension @<Extension>*;" +
          "\n    fhir:link @<$refType$> OR CLOSED {a [fhir:$refType$]}?;" +
          "\n    fhir:Reference.reference @<string>?;" +
          "\n    fhir:Reference.display @<string>?;" +
          "\n    fhir:index xsd:integer?" +
          "\n}";

  private static String TARGET_REFERENCE_TEMPLATE = "\n<$refType$> {" +
          "\n    a [fhir:$refType$];" +
          "\n    fhir:nodeRole [fhir:treeRoot]?" +
          "\n}";

  // A value set definition
  private static String VALUE_SET_DEFINITION = "# $comment$\n$vsuri$$val_list$\n";


  /**
   * this makes internal metadata services available to the generator - retrieving structure definitions, and value set expansion etc
   */
  private IWorkerContext context;
  private ProfileUtilities profileUtilities;

  /**
   * innerTypes -- inner complex types.  Currently flattened in ShEx (doesn't have to be, btw)
   * emittedInnerTypes -- set of inner types that have been generated
   * datatypes, emittedDatatypes -- types used in the definition, types that have been generated
   * references -- Reference types (Patient, Specimen, etc)
   * uniq_structures -- set of structures on the to be generated list...
   * doDataTypes -- whether or not to emit the data types.
   */
  private HashSet<Pair<StructureDefinition, ElementDefinition>> innerTypes, emittedInnerTypes;
  private HashSet<String> datatypes, emittedDatatypes;
  private HashSet<String> references;
  private LinkedList<StructureDefinition> uniq_structures;
  private HashSet<String> uniq_structure_urls;
  private HashSet<ValueSet> required_value_sets;
  private HashSet<String> known_resources;          // Used when generating a full definition

  public ShExGenerator(IWorkerContext context) {
    super();
    this.context = context;
    profileUtilities = new ProfileUtilities(context, null, null);
    innerTypes = new HashSet<Pair<StructureDefinition, ElementDefinition>>();
    emittedInnerTypes = new HashSet<Pair<StructureDefinition, ElementDefinition>>();
    datatypes = new HashSet<String>();
    emittedDatatypes = new HashSet<String>();
    references = new HashSet<String>();
    required_value_sets = new HashSet<ValueSet>();
    known_resources = new HashSet<String>();
  }

  public String generate(HTMLLinkPolicy links, StructureDefinition structure) {
    List<StructureDefinition> list = new ArrayList<StructureDefinition>();
    list.add(structure);
    innerTypes.clear();
    emittedInnerTypes.clear();
    datatypes.clear();
    emittedDatatypes.clear();
    references.clear();
    required_value_sets.clear();
    known_resources.clear();
    return generate(links, list);
  }

  public class SortById implements Comparator<StructureDefinition> {

    @Override
    public int compare(StructureDefinition arg0, StructureDefinition arg1) {
      return arg0.getId().compareTo(arg1.getId());
    }

  }

  private ST tmplt(String template) {
    return new ST(template, '$', '$');
  }

  /**
   * this is called externally to generate a set of structures to a single ShEx file
   * generally, it will be called with a single structure, or a long list of structures (all of them)
   *
   * @param links HTML link rendering policy
   * @param structures list of structure definitions to render
   * @return ShEx definition of structures
   */
  public String generate(HTMLLinkPolicy links, List<StructureDefinition> structures) {

    ST shex_def = tmplt(SHEX_TEMPLATE);
    String start_cmd;
    if(completeModel || structures.get(0).getKind().equals(StructureDefinition.StructureDefinitionKind.RESOURCE))
//            || structures.get(0).getKind().equals(StructureDefinition.StructureDefinitionKind.COMPLEXTYPE))
      start_cmd = completeModel? tmplt(ALL_START_TEMPLATE).render() :
              tmplt(START_TEMPLATE).add("id", structures.get(0).getId()).render();
    else
      start_cmd = "";
    shex_def.add("header", tmplt(HEADER_TEMPLATE).
            add("start", start_cmd).
            add("fhir", FHIR).
            add("fhirvs", FHIR_VS).render());

    Collections.sort(structures, new SortById());
    StringBuilder shapeDefinitions = new StringBuilder();

    // For unknown reasons, the list of structures carries duplicates.  We remove them
    // Also, it is possible for the same sd to have multiple hashes...
    uniq_structures = new LinkedList<StructureDefinition>();
    uniq_structure_urls = new HashSet<String>();
    for (StructureDefinition sd : structures) {
      if (!uniq_structure_urls.contains(sd.getUrl())) {
        uniq_structures.add(sd);
        uniq_structure_urls.add(sd.getUrl());
      }
    }


    for (StructureDefinition sd : uniq_structures) {
      shapeDefinitions.append(genShapeDefinition(sd, true));
    }

    shapeDefinitions.append(emitInnerTypes());
    if(doDatatypes) {
      shapeDefinitions.append("\n#---------------------- Data Types -------------------\n");
      while (emittedDatatypes.size() < datatypes.size() ||
              emittedInnerTypes.size() < innerTypes.size()) {
        shapeDefinitions.append(emitDataTypes());
        shapeDefinitions.append(emitInnerTypes());
      }
    }

    shapeDefinitions.append("\n#---------------------- Reference Types -------------------\n");
    for(String r: references) {
      shapeDefinitions.append("\n").append(tmplt(TYPED_REFERENCE_TEMPLATE).add("refType", r).render()).append("\n");
      if (!"Resource".equals(r) && !known_resources.contains(r))
        shapeDefinitions.append("\n").append(tmplt(TARGET_REFERENCE_TEMPLATE).add("refType", r).render()).append("\n");
    }
    shex_def.add("shapeDefinitions", shapeDefinitions);

    if(completeModel && known_resources.size() > 0) {
      shapeDefinitions.append("\n").append(tmplt(COMPLETE_RESOURCE_TEMPLATE)
              .add("resources", StringUtils.join(known_resources, "> OR\n\t@<")).render());
      List<String> all_entries = new ArrayList<String>();
      for(String kr: known_resources)
        all_entries.add(tmplt(ALL_ENTRY_TEMPLATE).add("id", kr).render());
      shapeDefinitions.append("\n").append(tmplt(ALL_TEMPLATE)
              .add("all_entries", StringUtils.join(all_entries, " OR\n\t")).render());
    }

    shapeDefinitions.append("\n#---------------------- Value Sets ------------------------\n");
    for(ValueSet vs: required_value_sets)
      shapeDefinitions.append("\n").append(genValueSet(vs));
    return shex_def.render();
  }


  /**
   * Emit a ShEx definition for the supplied StructureDefinition
   * @param sd Structure definition to emit
   * @param top_level True means outermost type, False means recursively called
   * @return ShEx definition
   */
  private String genShapeDefinition(StructureDefinition sd, boolean top_level) {
    // xhtml is treated as an atom
    if("xhtml".equals(sd.getName()) || (completeModel && "Resource".equals(sd.getName())))
      return "";

    ST shape_defn;
    // Resources are either incomplete items or consist of everything that is defined as a resource (completeModel)
    if("Resource".equals(sd.getName())) {
      shape_defn = tmplt(RESOURCE_SHAPE_TEMPLATE);
      known_resources.add(sd.getName());
    } else {
      shape_defn = tmplt(SHAPE_DEFINITION_TEMPLATE).add("id", sd.getId());
      if (sd.getKind().equals(StructureDefinition.StructureDefinitionKind.RESOURCE)) {
//              || sd.getKind().equals(StructureDefinition.StructureDefinitionKind.COMPLEXTYPE)) {
        known_resources.add(sd.getName());
        ST resource_decl = tmplt(RESOURCE_DECL_TEMPLATE).
                add("id", sd.getId()).
                add("root", tmplt(ROOT_TEMPLATE));
//                add("root", top_level ? tmplt(ROOT_TEMPLATE) : "");
        shape_defn.add("resourceDecl", resource_decl.render());
      } else {
        shape_defn.add("resourceDecl", "");
      }
    }

    // Generate the defining elements
    List<String> elements = new ArrayList<String>();

    // Add the additional entries for special types
    String sdn = sd.getName();
    if (sdn.equals("Coding"))
      elements.add(tmplt(CONCEPT_REFERENCE_TEMPLATE).render());
    else if (sdn.equals("CodeableConcept"))
      elements.add(tmplt(CONCEPT_REFERENCES_TEMPLATE).render());
    else if (sdn.equals("Reference"))
      elements.add(tmplt(RESOURCE_LINK_TEMPLATE).render());
//    else if (sdn.equals("Extension"))
//      return tmplt(EXTENSION_TEMPLATE).render();

    String root_comment = null;
    for (ElementDefinition ed : sd.getSnapshot().getElement()) {
      if(!ed.getPath().contains("."))
        root_comment = ed.getShort();
      else if (StringUtils.countMatches(ed.getPath(), ".") == 1 && !"0".equals(ed.getMax())) {
        elements.add(genElementDefinition(sd, ed));
      }
    }
    shape_defn.add("elements", StringUtils.join(elements, "\n"));
    shape_defn.add("comment", root_comment == null? " " : "# " + root_comment);
    return shape_defn.render();
  }


  /**
   * Generate a flattened definition for the inner types
   * @return stringified inner type definitions
   */
  private String emitInnerTypes() {
    StringBuilder itDefs = new StringBuilder();
    while(emittedInnerTypes.size() < innerTypes.size()) {
      for (Pair<StructureDefinition, ElementDefinition> it : new HashSet<Pair<StructureDefinition, ElementDefinition>>(innerTypes)) {
        if (!emittedInnerTypes.contains(it)) {
          itDefs.append("\n").append(genInnerTypeDef(it.getLeft(), it.getRight()));
          emittedInnerTypes.add(it);
        }
      }
    }
    return itDefs.toString();
  }

  /**
   * Generate a shape definition for the current set of datatypes
   * @return stringified data type definitions
   */
  private String emitDataTypes() {
    StringBuilder dtDefs = new StringBuilder();
    while (emittedDatatypes.size() < datatypes.size()) {
      for (String dt : new HashSet<String>(datatypes)) {
        if (!emittedDatatypes.contains(dt)) {
          StructureDefinition sd = context.fetchResource(StructureDefinition.class,
              ProfileUtilities.sdNs(dt, null));
          // TODO: Figure out why the line below doesn't work
          // if (sd != null && !uniq_structures.contains(sd))
          if(sd != null && !uniq_structure_urls.contains(sd.getUrl()))
            dtDefs.append("\n").append(genShapeDefinition(sd, false));
          emittedDatatypes.add(dt);
        }
      }
    }
    return dtDefs.toString();
  }

  private ArrayList<String> split_text(String text, int max_col) {
    int pos = 0;
    ArrayList<String> rval = new ArrayList<String>();
    if (text.length() <= max_col) {
      rval.add(text);
    } else {
      String[] words = text.split(" ");
      int word_idx = 0;
      while(word_idx < words.length) {
        StringBuilder accum = new StringBuilder();
        while (word_idx < words.length && accum.length() + words[word_idx].length() < max_col)
          accum.append(words[word_idx++] + " ");
        if (accum.length() == 0) {
          accum.append(words[word_idx].substring(0, max_col - 3) + "-");
          words[word_idx] = words[word_idx].substring(max_col - 3);
        }
        rval.add(accum.toString());
        accum = new StringBuilder();
      }
    }
    return rval;
  }

  private void addComment(ST tmplt, ElementDefinition ed) {
    if(withComments && ed.hasShort() && !ed.getId().startsWith("Extension.")) {
      int nspaces;
      char[] sep;
      nspaces = Integer.max(COMMENT_COL - tmplt.add("comment", "#").render().indexOf('#'), MIN_COMMENT_SEP);
      tmplt.remove("comment");
      sep = new char[nspaces];
      Arrays.fill(sep, ' ');
      ArrayList<String> comment_lines = split_text(ed.getShort().replace("\n", " "), MAX_CHARS);
      StringBuilder comment = new StringBuilder("# ");
      char[] indent = new char[COMMENT_COL];
      Arrays.fill(indent, ' ');
      for(int i = 0; i < comment_lines.size();) {
        comment.append(comment_lines.get(i++));
        if(i < comment_lines.size())
          comment.append("\n" + new String(indent) + "# ");
      }
      tmplt.add("comment", new String(sep) + comment.toString());
    } else {
      tmplt.add("comment", " ");
    }
  }


  /**
   * Generate a ShEx element definition
   * @param sd Containing structure definition
   * @param ed Containing element definition
   * @return ShEx definition
   */
  private String genElementDefinition(StructureDefinition sd, ElementDefinition ed) {
    String id = ed.hasBase() ? ed.getBase().getPath() : ed.getPath();
    String shortId = id.substring(id.lastIndexOf(".") + 1);
    String defn;
    ST element_def;
    String card = ("*".equals(ed.getMax()) ? (ed.getMin() == 0 ? "*" : "+") : (ed.getMin() == 0 ? "?" : "")) + ";";

    if(id.endsWith("[x]")) {
      element_def = ed.getType().size() > 1? tmplt(INNER_SHAPE_TEMPLATE) : tmplt(ELEMENT_TEMPLATE);
      element_def.add("id", "");
    } else {
      element_def = tmplt(ELEMENT_TEMPLATE);
      element_def.add("id", "fhir:" + (id.charAt(0) == id.toLowerCase().charAt(0)? shortId : id) + " ");
    }

    List<ElementDefinition> children = profileUtilities.getChildList(sd, ed);
    if (children.size() > 0) {
      innerTypes.add(new ImmutablePair<StructureDefinition, ElementDefinition>(sd, ed));
      defn = simpleElement(sd, ed, id);
    } else if(id.endsWith("[x]")) {
      defn = genChoiceTypes(sd, ed, id);
    }
    else if (ed.getType().size() == 1) {
      // Single entry
      defn = genTypeRef(sd, ed, id, ed.getType().get(0));
    } else if (ed.getContentReference() != null) {
      // Reference to another element
      String ref = ed.getContentReference();
      if(!ref.startsWith("#"))
        throw new AssertionError("Not equipped to deal with absolute path references: " + ref);
      String refPath = null;
      for(ElementDefinition ed1: sd.getSnapshot().getElement()) {
        if(ed1.getId() != null && ed1.getId().equals(ref.substring(1))) {
          refPath = ed1.getPath();
          break;
        }
      }
      if(refPath == null)
        throw new AssertionError("Reference path not found: " + ref);
      // String typ = id.substring(0, id.indexOf(".") + 1) + ed.getContentReference().substring(1);
      defn = simpleElement(sd, ed, refPath);
    } else if(id.endsWith("[x]")) {
      defn = genChoiceTypes(sd, ed, id);
    } else {
      // TODO: Refactoring required here
      element_def = genAlternativeTypes(ed, id, shortId);
      element_def.add("id", id.charAt(0) == id.toLowerCase().charAt(0)? shortId : id);
      element_def.add("card", card);
      addComment(element_def, ed);
      return element_def.render();
    }
    element_def.add("defn", defn);
    element_def.add("card", card);
    addComment(element_def, ed);
    return element_def.render();
  }

  /**
   * Generate a type reference and optional value set definition
   * @param sd Containing StructureDefinition
   * @param ed Element being defined
   * @param typ Element type
   * @return Type definition
   */
  private String simpleElement(StructureDefinition sd, ElementDefinition ed, String typ) {
    String addldef = "";
    ElementDefinition.ElementDefinitionBindingComponent binding = ed.getBinding();
    if(binding.hasStrength() && binding.getStrength() == Enumerations.BindingStrength.REQUIRED && "code".equals(typ)) {
      ValueSet vs = resolveBindingReference(sd, binding.getValueSet());
      if (vs != null) {
        addldef = tmplt(VALUESET_DEFN_TEMPLATE).add("vsn", vsprefix(vs.getUrl())).render();
        required_value_sets.add(vs);
      }
    }
    // TODO: check whether value sets and fixed are mutually exclusive
    if(ed.hasFixed()) {
      addldef = tmplt(FIXED_VALUE_TEMPLATE).add("val", ed.getFixed().primitiveValue()).render();
    }
    return tmplt(SIMPLE_ELEMENT_DEFN_TEMPLATE).add("typ", typ).add("vsdef", addldef).render();
  }

  private String vsprefix(String uri) {
    if(uri.startsWith(FHIR_VS))
      return "fhirvs:" + uri.replace(FHIR_VS, "");
    return "<" + uri + ">";
  }

  /**
   * Generate a type reference
   * @param sd Containing structure definition
   * @param ed Containing element definition
   * @param id Element id
   * @param typ Element type
   * @return Type reference string
   */
  private String genTypeRef(StructureDefinition sd, ElementDefinition ed, String id, ElementDefinition.TypeRefComponent typ) {

    if(typ.hasProfile()) {
      if(typ.getWorkingCode().equals("Reference"))
        return genReference("", typ);
      else if(profileUtilities.getChildList(sd, ed).size() > 0) {
        // inline anonymous type - give it a name and factor it out
        innerTypes.add(new ImmutablePair<StructureDefinition, ElementDefinition>(sd, ed));
        return simpleElement(sd, ed, id);
      }
      else {
        String ref = getTypeName(typ);
        datatypes.add(ref);
        return simpleElement(sd, ed, ref);
      }

    } else if (typ.getCode().startsWith(Constants.NS_SYSTEM_TYPE)) {
      String xt = getShexCode(typ.getWorkingCode());
      
      // TODO: Remove the next line when the type of token gets switched to string
      // TODO: Add a rdf-type entry for valueInteger to xsd:integer (instead of int)
      ST td_entry = tmplt(PRIMITIVE_ELEMENT_DEFN_TEMPLATE).add("typ", xt);
      StringBuilder facets =  new StringBuilder();
      if(ed.hasMinValue()) {
        DataType mv = ed.getMinValue();
        facets.append(tmplt(MINVALUE_TEMPLATE).add("val", mv.primitiveValue()).render());
      }
      if(ed.hasMaxValue()) {
        DataType mv = ed.getMaxValue();
        facets.append(tmplt(MAXVALUE_TEMPLATE).add("val", mv.primitiveValue()).render());
      }
      if(ed.hasMaxLength()) {
        int ml = ed.getMaxLength();
        facets.append(tmplt(MAXLENGTH_TEMPLATE).add("val", ml).render());
      }
      if(ed.hasPattern()) {
        DataType pat = ed.getPattern();
        facets.append(tmplt(PATTERN_TEMPLATE).add("val",pat.primitiveValue()).render());
      }
      td_entry.add("facets", facets.toString());
      return td_entry.render();

    } else if (typ.getWorkingCode() == null) {
      ST primitive_entry = tmplt(PRIMITIVE_ELEMENT_DEFN_TEMPLATE);
      primitive_entry.add("typ", "xsd:string");
      return primitive_entry.render();

    } else if(typ.getWorkingCode().equals("xhtml")) {
      return tmplt(XHTML_TYPE_TEMPLATE).render();
    } else {
      datatypes.add(typ.getWorkingCode());
      return simpleElement(sd, ed, typ.getWorkingCode());
    }
  }

  private String getShexCode(String c) {
    switch (c) {
    case "boolean" : 
      return "xsd:boolean";
    case "integer" : 
      return "xsd:int";
    case "integer64" : 
      return "xsd:long";
    case "decimal" : 
      return "xsd:decimal, xsd:double";
    case "base64Binary" : 
      return "xsd:base64Binary";
    case "instant" : 
      return "xsd:dateTime";
    case "string" : 
      return "xsd:string";
    case "uri" : 
      return "xsd:anyURI";
    case "date" : 
      return "xsd:gYear, xsd:gYearMonth, xsd:date";
    case "dateTime" : 
      return "xsd:gYear, xsd:gYearMonth, xsd:date, xsd:dateTime";
    case "time" : 
      return "xsd:time";
    case "code" : 
      return "xsd:token";
    case "oid" : 
      return "xsd:anyURI";
    case "uuid" : 
      return "xsd:anyURI";
    case "url" : 
      return "xsd:anyURI";
    case "canonical" : 
      return "xsd:anyURI";
    case "id" : 
      return "xsd:string";
    case "unsignedInt" : 
      return "xsd:nonNegativeInteger";
    case "positiveInt" : 
      return "xsd:positiveInteger";
    case "markdown" : 
      return "xsd:string";
    }
    throw new Error("Not implemented yet");
      
  }

  /**
   * Generate a set of alternative shapes
   * @param ed Containing element definition
   * @param id Element definition identifier
   * @param shortId id to use in the actual definition
   * @return ShEx list of alternative anonymous shapes separated by "OR"
   */
  private ST genAlternativeTypes(ElementDefinition ed, String id, String shortId) {
    ST shex_alt = tmplt(ALTERNATIVE_SHAPES_TEMPLATE);
    List<String> altEntries = new ArrayList<String>();


    for(ElementDefinition.TypeRefComponent typ : ed.getType())  {
      altEntries.add(genAltEntry(id, typ));
    }
    shex_alt.add("altEntries", StringUtils.join(altEntries, " OR\n    "));
    return shex_alt;
  }



  /**
   * Generate an alternative shape for a reference
   * @param id reference name
   * @param typ shape type
   * @return ShEx equivalent
   */
  private String genAltEntry(String id, ElementDefinition.TypeRefComponent typ) {
    if(!typ.getWorkingCode().equals("Reference"))
      throw new AssertionError("We do not handle " + typ.getWorkingCode() + " alternatives");

    return genReference(id, typ);
  }

  /**
   * Generate a list of type choices for a "name[x]" style id
   * @param sd Structure containing ed
   * @param ed element definition
   * @param id choice identifier
   * @return ShEx fragment for the set of choices
   */
  private String genChoiceTypes(StructureDefinition sd, ElementDefinition ed, String id) {
    List<String> choiceEntries = new ArrayList<String>();
    String base = id.replace("[x]", "");

    for(ElementDefinition.TypeRefComponent typ : ed.getType())
      choiceEntries.add(genChoiceEntry(sd, ed, id, base, typ));

    return StringUtils.join(choiceEntries, " |\n");
  }

  /**
   * Generate an entry in a choice list
   * @param base base identifier
   * @param typ type/discriminant
   * @return ShEx fragment for choice entry
   */
  private String genChoiceEntry(StructureDefinition sd, ElementDefinition ed, String id, String base, ElementDefinition.TypeRefComponent typ) {
    ST shex_choice_entry = tmplt(ELEMENT_TEMPLATE);

    String ext = typ.getWorkingCode();
    shex_choice_entry.add("id", "fhir:" + base+Character.toUpperCase(ext.charAt(0)) + ext.substring(1) + " ");
    shex_choice_entry.add("card", "");
    shex_choice_entry.add("defn", genTypeRef(sd, ed, id, typ));
    shex_choice_entry.add("comment", " ");
    return shex_choice_entry.render();
  }

  /**
   * Generate a definition for a referenced element
   * @param sd Containing structure definition
   * @param ed Inner element
   * @return ShEx representation of element reference
   */
  private String genInnerTypeDef(StructureDefinition sd, ElementDefinition ed) {
    String path = ed.hasBase() ? ed.getBase().getPath() : ed.getPath();;
    ST element_reference = tmplt(SHAPE_DEFINITION_TEMPLATE);
    element_reference.add("resourceDecl", "");  // Not a resource
    element_reference.add("id", path);
    String comment = ed.getShort();
    element_reference.add("comment", comment == null? " " : "# " + comment);

    List<String> elements = new ArrayList<String>();
    for (ElementDefinition child: profileUtilities.getChildList(sd, path, null))
      elements.add(genElementDefinition(sd, child));

    element_reference.add("elements", StringUtils.join(elements, "\n"));
    return element_reference.render();
  }

  /**
   * Generate a reference to a resource
   * @param id attribute identifier
   * @param typ possible reference types
   * @return string that represents the result
   */
  private String genReference(String id, ElementDefinition.TypeRefComponent typ) {
    ST shex_ref = tmplt(REFERENCE_DEFN_TEMPLATE);

    String ref = getTypeName(typ);
    shex_ref.add("id", id);
    shex_ref.add("ref", ref);
    references.add(ref);
    return shex_ref.render();
  }

  /**
   * Return the type name for typ
   * @param typ type to get name for
   * @return name
   */
  private String getTypeName(ElementDefinition.TypeRefComponent typ) {
    // TODO: This is brittle. There has to be a utility to do this...
    if (typ.hasTargetProfile()) {
      String[] els = typ.getTargetProfile().get(0).getValue().split("/");
      return els[els.length - 1];
    } else if (typ.hasProfile()) {
      String[] els = typ.getProfile().get(0).getValue().split("/");
      return els[els.length - 1];
    } else {
      return typ.getWorkingCode();
    }
  }

  private String genValueSet(ValueSet vs) {
    ST vsd = tmplt(VALUE_SET_DEFINITION).add("vsuri", vsprefix(vs.getUrl())).add("comment", vs.getDescription());
    ValueSetExpander.ValueSetExpansionOutcome vse = context.expandVS(vs, true, false);
    List<String> valid_codes = new ArrayList<String>();
    if(vse != null &&
            vse.getValueset() != null &&
            vse.getValueset().hasExpansion() &&
            vse.getValueset().getExpansion().hasContains()) {
      for(ValueSet.ValueSetExpansionContainsComponent vsec : vse.getValueset().getExpansion().getContains())
        valid_codes.add("\"" + vsec.getCode() + "\"");
    }
    return vsd.add("val_list", valid_codes.size() > 0? " [" + StringUtils.join(valid_codes, " ") + ']' : " EXTERNAL").render();
  }


  // TODO: find a utility that implements this
  private ValueSet resolveBindingReference(DomainResource ctxt, String reference) {
    try {
      return context.fetchResource(ValueSet.class, reference);
    } catch (Throwable e) {
      return null;
    }
  }
}