/**

  * Back 2 Browser Bytecode Translator

  * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>

  *

  * This program is free software: you can redistribute it and/or modify

  * it under the terms of the GNU General Public License as published by

  * the Free Software Foundation, version 2 of the License.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  *

  * You should have received a copy of the GNU General Public License

  * along with this program. Look for COPYING file in the top folder.

  * If not, see http://opensource.org/licenses/GPL-2.0.

  */

 package org.apidesign.bck2brwsr.htmlpage;

 import java.io.IOException;

 import java.io.InputStream;

 import java.io.OutputStreamWriter;

 import java.io.StringWriter;

 import java.io.Writer;

 import java.util.ArrayList;

 import java.util.Collection;

 import java.util.Collections;

 import java.util.HashMap;

 import java.util.LinkedHashSet;

 import java.util.List;

 import java.util.Map;

 import java.util.Set;

 import java.util.WeakHashMap;

 import javax.annotation.processing.AbstractProcessor;

 import javax.annotation.processing.Completion;

 import javax.annotation.processing.Completions;

 import javax.annotation.processing.Messager;

 import javax.annotation.processing.Processor;

 import javax.annotation.processing.RoundEnvironment;

 import javax.annotation.processing.SupportedAnnotationTypes;

 import javax.lang.model.element.AnnotationMirror;

 import javax.lang.model.element.Element;

 import javax.lang.model.element.ElementKind;

 import javax.lang.model.element.ExecutableElement;

 import javax.lang.model.element.Modifier;

 import javax.lang.model.element.PackageElement;

 import javax.lang.model.element.TypeElement;

 import javax.lang.model.element.VariableElement;

 import javax.lang.model.type.ArrayType;

 import javax.lang.model.type.DeclaredType;

 import javax.lang.model.type.MirroredTypeException;

 import javax.lang.model.type.TypeKind;

 import javax.lang.model.type.TypeMirror;

 import javax.lang.model.util.Elements;

 import javax.lang.model.util.Types;

 import javax.tools.Diagnostic;

 import javax.tools.FileObject;

 import javax.tools.StandardLocation;

 import org.apidesign.bck2brwsr.htmlpage.api.ComputedProperty;

 import org.apidesign.bck2brwsr.htmlpage.api.Model;

 import org.apidesign.bck2brwsr.htmlpage.api.On;

 import org.apidesign.bck2brwsr.htmlpage.api.OnFunction;

 import org.apidesign.bck2brwsr.htmlpage.api.OnReceive;

 import org.apidesign.bck2brwsr.htmlpage.api.Page;

 import org.apidesign.bck2brwsr.htmlpage.api.Property;

 import org.openide.util.lookup.ServiceProvider;

 /** Annotation processor to process an XHTML page and generate appropriate 

  * "id" file.

  *

  * @author Jaroslav Tulach <jtulach@netbeans.org>

  */

 @ServiceProvider(service=Processor.class)

 @SupportedAnnotationTypes({

     "org.apidesign.bck2brwsr.htmlpage.api.Model",

     "org.apidesign.bck2brwsr.htmlpage.api.Page",

     "org.apidesign.bck2brwsr.htmlpage.api.OnFunction",

     "org.apidesign.bck2brwsr.htmlpage.api.OnReceive",

     "org.apidesign.bck2brwsr.htmlpage.api.On"

 })

 public final class PageProcessor extends AbstractProcessor {

     private final Map<Element,String> models = new WeakHashMap<>();

     @Override

     public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {

         boolean ok = true;

         for (Element e : roundEnv.getElementsAnnotatedWith(Model.class)) {

             if (!processModel(e)) {

                 ok = false;

             }

         }

         for (Element e : roundEnv.getElementsAnnotatedWith(Page.class)) {

             if (!processPage(e)) {

                 ok = false;

             }

         }

         if (roundEnv.processingOver()) {

             models.clear();

         }

         return ok;

     }

     private InputStream openStream(String pkg, String name) throws IOException {

         try {

             FileObject fo = processingEnv.getFiler().getResource(

                 StandardLocation.SOURCE_PATH, pkg, name);

             return fo.openInputStream();

         } catch (IOException ex) {

             return processingEnv.getFiler().getResource(StandardLocation.CLASS_OUTPUT, pkg, name).openInputStream();

         }

     }

     private  Messager err() {

         return processingEnv.getMessager();

     }

     private boolean processModel(Element e) {

         boolean ok = true;

         Model m = e.getAnnotation(Model.class);

         if (m == null) {

             return true;

         }

         String pkg = findPkgName(e);

         Writer w;

         String className = m.className();

         models.put(e, className);

         try {

             StringWriter body = new StringWriter();

             List<String> propsGetSet = new ArrayList<>();

             List<String> functions = new ArrayList<>();

             Map<String, Collection<String>> propsDeps = new HashMap<>();

             if (!generateComputedProperties(body, m.properties(), e.getEnclosedElements(), propsGetSet, propsDeps)) {

                 ok = false;

             }

             if (!generateProperties(e, body, m.properties(), propsGetSet, propsDeps)) {

                 ok = false;

             }

             if (!generateFunctions(e, body, className, e.getEnclosedElements(), functions)) {

                 ok = false;

             }

             FileObject java = processingEnv.getFiler().createSourceFile(pkg + '.' + className, e);

             w = new OutputStreamWriter(java.openOutputStream());

             try {

                 w.append("package " + pkg + ";\n");

                 w.append("import org.apidesign.bck2brwsr.htmlpage.api.*;\n");

                 w.append("import org.apidesign.bck2brwsr.htmlpage.KOList;\n");

                 w.append("import org.apidesign.bck2brwsr.core.JavaScriptOnly;\n");

                 w.append("final class ").append(className).append(" implements Cloneable {\n");

                 w.append("  private boolean locked;\n");

                 w.append("  private org.apidesign.bck2brwsr.htmlpage.Knockout ko;\n");

                 w.append(body.toString());

                 w.append("  private static Class<" + inPckName(e) + "> modelFor() { return null; }\n");

                 w.append("  public ").append(className).append("() {\n");

                 w.append("    intKnckt();\n");

                 w.append("  };\n");

                 w.append("  private void intKnckt() {\n");

                 w.append("    ko = org.apidesign.bck2brwsr.htmlpage.Knockout.applyBindings(this, ");

                 writeStringArray(propsGetSet, w);

                 w.append(", ");

                 writeStringArray(functions, w);

                 w.append("    );\n");

                 w.append("  };\n");

                 w.append("  ").append(className).append("(Object json) {\n");

                 int values = 0;

                 for (int i = 0; i < propsGetSet.size(); i += 4) {

                     if (propsGetSet.get(i + 2) == null) {

                         continue;

                     }

                     values++;

                 }

                 w.append("    Object[] ret = new Object[" + values + "];\n");

                 w.append("    org.apidesign.bck2brwsr.htmlpage.ConvertTypes.extractJSON(json, new String[] {\n");

                 for (int i = 0; i < propsGetSet.size(); i += 4) {

                     if (propsGetSet.get(i + 2) == null) {

                         continue;

                     }

                     w.append("      \"").append(propsGetSet.get(i)).append("\",\n");

                 }

                 w.append("    }, ret);\n");

                 for (int i = 0, cnt = 0, prop = 0; i < propsGetSet.size(); i += 4) {

                     if (propsGetSet.get(i + 2) == null) {

                         continue;

                     }

                     boolean[] isModel = { false };

                     boolean[] isEnum = { false };

                     String type = checkType(m.properties()[prop++], isModel, isEnum);

                     w.append("    this.prop_").append(propsGetSet.get(i)).append(" = ");

                     boolean close = false;

                     if (isEnum[0]) {

 //                        w.append(type).append(".valueOf((String)");

 //                        close = true;

                         w.append("null;\n");

                         continue;

                     } else {

                         w.append('(').append(type).append(')');

                     }

                     w.append("ret[" + cnt++ + "]");

                     if (close) {

                         w.append(");\n");

                     } else {

                         w.append(";\n");

                     }

                 }

                 w.append("    intKnckt();\n");

                 w.append("  };\n");

                 writeToString(m.properties(), w);

                 writeClone(className, m.properties(), w);

                 w.append("}\n");

             } finally {

                 w.close();

             }

         } catch (IOException ex) {

             err().printMessage(Diagnostic.Kind.ERROR, "Can't create " + className + ".java", e);

             return false;

         }

         return ok;

     }

     private boolean processPage(Element e) {

         boolean ok = true;

         Page p = e.getAnnotation(Page.class);

         if (p == null) {

             return true;

         }

         String pkg = findPkgName(e);

         ProcessPage pp;

         try (InputStream is = openStream(pkg, p.xhtml())) {

             pp = ProcessPage.readPage(is);

             is.close();

         } catch (IOException iOException) {

             err().printMessage(Diagnostic.Kind.ERROR, "Can't read " + p.xhtml() + " as " + iOException.getMessage(), e);

             ok = false;

             pp = null;

         }

         Writer w;

         String className = p.className();

         if (className.isEmpty()) {

             int indx = p.xhtml().indexOf('.');

             className = p.xhtml().substring(0, indx);

         }

         try {

             StringWriter body = new StringWriter();

             List<String> propsGetSet = new ArrayList<>();

             List<String> functions = new ArrayList<>();

             Map<String, Collection<String>> propsDeps = new HashMap<>();

             if (!generateComputedProperties(body, p.properties(), e.getEnclosedElements(), propsGetSet, propsDeps)) {

                 ok = false;

             }

             if (!generateProperties(e, body, p.properties(), propsGetSet, propsDeps)) {

                 ok = false;

             }

             if (!generateFunctions(e, body, className, e.getEnclosedElements(), functions)) {

                 ok = false;

             }

             if (!generateReceive(e, body, className, e.getEnclosedElements(), functions)) {

                 ok = false;

             }

             FileObject java = processingEnv.getFiler().createSourceFile(pkg + '.' + className, e);

             w = new OutputStreamWriter(java.openOutputStream());

             try {

                 w.append("package " + pkg + ";\n");

                 w.append("import org.apidesign.bck2brwsr.htmlpage.api.*;\n");

                 w.append("import org.apidesign.bck2brwsr.htmlpage.KOList;\n");

                 w.append("final class ").append(className).append(" {\n");

                 w.append("  private boolean locked;\n");

                 if (!initializeOnClick(className, (TypeElement) e, w, pp)) {

                     ok = false;

                 } else {

                     if (pp != null) for (String id : pp.ids()) {

                         String tag = pp.tagNameForId(id);

                         String type = type(tag);

                         w.append("  ").append("public final ").

                             append(type).append(' ').append(cnstnt(id)).append(" = new ").

                             append(type).append("(\"").append(id).append("\");\n");

                     }

                 }

                 w.append("  private org.apidesign.bck2brwsr.htmlpage.Knockout ko;\n");

                 w.append(body.toString());

                 if (!propsGetSet.isEmpty()) {

                     w.write("public " + className + " applyBindings() {\n");

                     w.write("  ko = org.apidesign.bck2brwsr.htmlpage.Knockout.applyBindings(");

                     w.write(className + ".class, this, ");

                     writeStringArray(propsGetSet, w);

                     w.append(", ");

                     writeStringArray(functions, w);

                     w.write(");\n  return this;\n}\n");

                     w.write("public void triggerEvent(Element e, OnEvent ev) {\n");

                     w.write("  org.apidesign.bck2brwsr.htmlpage.Knockout.triggerEvent(e.getId(), ev.getElementPropertyName());\n");

                     w.write("}\n");

                 }

                 w.append("}\n");

             } finally {

                 w.close();

             }

         } catch (IOException ex) {

             err().printMessage(Diagnostic.Kind.ERROR, "Can't create " + className + ".java", e);

             return false;

         }

         return ok;

     }

     private static String type(String tag) {

         if (tag.equals("title")) {

             return "Title";

         }

         if (tag.equals("button")) {

             return "Button";

         }

         if (tag.equals("input")) {

             return "Input";

         }

         if (tag.equals("canvas")) {

             return "Canvas";

         }

         if (tag.equals("img")) {

             return "Image";

         }

         return "Element";

     }

     private static String cnstnt(String id) {

         return id.replace('.', '_').replace('-', '_');

     }

     private boolean initializeOnClick(

         String className, TypeElement type, Writer w, ProcessPage pp

     ) throws IOException {

         boolean ok = true;

         TypeMirror stringType = processingEnv.getElementUtils().getTypeElement("java.lang.String").asType();

         { //for (Element clazz : pe.getEnclosedElements()) {

           //  if (clazz.getKind() != ElementKind.CLASS) {

             //    continue;

            // }

             w.append("  public ").append(className).append("() {\n");

             StringBuilder dispatch = new StringBuilder();

             int dispatchCnt = 0;

             for (Element method : type.getEnclosedElements()) {

                 On oc = method.getAnnotation(On.class);

                 if (oc != null) {

                     for (String id : oc.id()) {

                         if (pp == null) {

                             err().printMessage(Diagnostic.Kind.ERROR, "id = " + id + " not found in HTML page.");

                             ok = false;

                             continue;

                         }

                         if (pp.tagNameForId(id) == null) {

                             err().printMessage(Diagnostic.Kind.ERROR, "id = " + id + " does not exist in the HTML page. Found only " + pp.ids(), method);

                             ok = false;

                             continue;

                         }

                         ExecutableElement ee = (ExecutableElement)method;

                         CharSequence params = wrapParams(ee, id, className, "ev", null);

                         if (!ee.getModifiers().contains(Modifier.STATIC)) {

                             err().printMessage(Diagnostic.Kind.ERROR, "@On method has to be static", ee);

                             ok = false;

                             continue;

                         }

                         if (ee.getModifiers().contains(Modifier.PRIVATE)) {

                             err().printMessage(Diagnostic.Kind.ERROR, "@On method can't be private", ee);

                             ok = false;

                             continue;

                         }

                         w.append("  OnEvent." + oc.event()).append(".of(").append(cnstnt(id)).

                             append(").perform(new OnDispatch(" + dispatchCnt + "));\n");

                         dispatch.

                             append("      case ").append(dispatchCnt).append(": ").

                             append(type.getSimpleName().toString()).

                             append('.').append(ee.getSimpleName()).append("(").

                             append(params).

                             append("); break;\n");

                         dispatchCnt++;

                     }

                 }

             }

             w.append("  }\n");

             if (dispatchCnt > 0) {

                 w.append("class OnDispatch implements OnHandler {\n");

                 w.append("  private final int dispatch;\n");

                 w.append("  OnDispatch(int d) { dispatch = d; }\n");

                 w.append("  public void onEvent(Object ev) {\n");

                 w.append("    switch (dispatch) {\n");

                 w.append(dispatch);

                 w.append("    }\n");

                 w.append("  }\n");

                 w.append("}\n");

             }

         }

         return ok;

     }

     @Override

     public Iterable<? extends Completion> getCompletions(

         Element element, AnnotationMirror annotation, 

         ExecutableElement member, String userText

     ) {

         if (!userText.startsWith("\"")) {

             return Collections.emptyList();

         }

         Element cls = findClass(element);

         Page p = cls.getAnnotation(Page.class);

         String pkg = findPkgName(cls);

         ProcessPage pp;

         try {

             InputStream is = openStream(pkg, p.xhtml());

             pp = ProcessPage.readPage(is);

             is.close();

         } catch (IOException iOException) {

             return Collections.emptyList();

         }

         List<Completion> cc = new ArrayList<>();

         userText = userText.substring(1);

         for (String id : pp.ids()) {

             if (id.startsWith(userText)) {

                 cc.add(Completions.of("\"" + id + "\"", id));

             }

         }

         return cc;

     }

     private static Element findClass(Element e) {

         if (e == null) {

             return null;

         }

         Page p = e.getAnnotation(Page.class);

         if (p != null) {

             return e;

         }

         return e.getEnclosingElement();

     }

     private boolean generateProperties(

         Element where,

         Writer w, Property[] properties,

         Collection<String> props, Map<String,Collection<String>> deps

     ) throws IOException {

         boolean ok = true;

         for (Property p : properties) {

             final String tn;

             tn = typeName(where, p);

             String[] gs = toGetSet(p.name(), tn, p.array());

             if (p.array()) {

                 w.write("private KOList<" + tn + "> prop_" + p.name() + " = new KOList<" + tn + ">(\""

                     + p.name() + "\"");

                 final Collection<String> dependants = deps.get(p.name());

                 if (dependants != null) {

                     for (String depProp : dependants) {

                         w.write(", ");

                         w.write('\"');

                         w.write(depProp);

                         w.write('\"');

                     }

                 }

                 w.write(");\n");

                 w.write("public java.util.List<" + tn + "> " + gs[0] + "() {\n");

                 w.write("  if (locked) throw new IllegalStateException();\n");

                 w.write("  prop_" + p.name() + ".assign(ko);\n");

                 w.write("  return prop_" + p.name() + ";\n");

                 w.write("}\n");

             } else {

                 w.write("private " + tn + " prop_" + p.name() + ";\n");

                 w.write("public " + tn + " " + gs[0] + "() {\n");

                 w.write("  if (locked) throw new IllegalStateException();\n");

                 w.write("  return prop_" + p.name() + ";\n");

                 w.write("}\n");

                 w.write("public void " + gs[1] + "(" + tn + " v) {\n");

                 w.write("  if (locked) throw new IllegalStateException();\n");

                 w.write("  prop_" + p.name() + " = v;\n");

                 w.write("  if (ko != null) {\n");

                 w.write("    ko.valueHasMutated(\"" + p.name() + "\");\n");

                 final Collection<String> dependants = deps.get(p.name());

                 if (dependants != null) {

                     for (String depProp : dependants) {

                         w.write("    ko.valueHasMutated(\"" + depProp + "\");\n");

                     }

                 }

                 w.write("  }\n");

                 w.write("}\n");

             }

             props.add(p.name());

             props.add(gs[2]);

             props.add(gs[3]);

             props.add(gs[0]);

         }

         return ok;

     }

     private boolean generateComputedProperties(

         Writer w, Property[] fixedProps,

         Collection<? extends Element> arr, Collection<String> props,

         Map<String,Collection<String>> deps

     ) throws IOException {

         boolean ok = true;

         for (Element e : arr) {

             if (e.getKind() != ElementKind.METHOD) {

                 continue;

             }

             if (e.getAnnotation(ComputedProperty.class) == null) {

                 continue;

             }

             ExecutableElement ee = (ExecutableElement)e;

             final TypeMirror rt = ee.getReturnType();

             final Types tu = processingEnv.getTypeUtils();

             TypeMirror ert = tu.erasure(rt);

             String tn = fqn(ert, ee);

             boolean array = false;

             if (tn.equals("java.util.List")) {

                 array = true;

             }

             final String sn = ee.getSimpleName().toString();

             String[] gs = toGetSet(sn, tn, array);

             w.write("public " + tn + " " + gs[0] + "() {\n");

             w.write("  if (locked) throw new IllegalStateException();\n");

             int arg = 0;

             for (VariableElement pe : ee.getParameters()) {

                 final String dn = pe.getSimpleName().toString();

                 if (!verifyPropName(pe, dn, fixedProps)) {

                     ok = false;

                 }

                 final String dt = fqn(pe.asType(), ee);

                 String[] call = toGetSet(dn, dt, false);

                 w.write("  " + dt + " arg" + (++arg) + " = ");

                 w.write(call[0] + "();\n");

                 Collection<String> depends = deps.get(dn);

                 if (depends == null) {

                     depends = new LinkedHashSet<>();

                     deps.put(dn, depends);

                 }

                 depends.add(sn);

             }

             w.write("  try {\n");

             w.write("    locked = true;\n");

             w.write("    return " + e.getEnclosingElement().getSimpleName() + '.' + e.getSimpleName() + "(");

             String sep = "";

             for (int i = 1; i <= arg; i++) {

                 w.write(sep);

                 w.write("arg" + i);

                 sep = ", ";

             }

             w.write(");\n");

             w.write("  } finally {\n");

             w.write("    locked = false;\n");

             w.write("  }\n");

             w.write("}\n");

             props.add(e.getSimpleName().toString());

             props.add(gs[2]);

             props.add(null);

             props.add(gs[0]);

         }

         return ok;

     }

     private static String[] toGetSet(String name, String type, boolean array) {

         String n = Character.toUpperCase(name.charAt(0)) + name.substring(1);

         String bck2brwsrType = "L" + type.replace('.', '_') + "_2";

         if ("int".equals(type)) {

             bck2brwsrType = "I";

         }

         if ("double".equals(type)) {

             bck2brwsrType = "D";

         }

         String pref = "get";

         if ("boolean".equals(type)) {

             pref = "is";

             bck2brwsrType = "Z";

         }

         final String nu = n.replace('.', '_');

         if (array) {

             return new String[] { 

                 "get" + n,

                 null,

                 "get" + nu + "__Ljava_util_List_2",

                 null

             };

         }

         return new String[]{

             pref + n, 

             "set" + n, 

             pref + nu + "__" + bck2brwsrType,

             "set" + nu + "__V" + bck2brwsrType

         };

     }

     private String typeName(Element where, Property p) {

         String ret;

         boolean[] isModel = { false };

         boolean[] isEnum = { false };

         ret = checkType(p, isModel, isEnum);

         if (p.array()) {

             String bt = findBoxedType(ret);

             if (bt != null) {

                 return bt;

             }

         }

         if (!isModel[0] && !"java.lang.String".equals(ret) && !isEnum[0]) {

             String bt = findBoxedType(ret);

             if (bt == null) {

                 err().printMessage(

                     Diagnostic.Kind.ERROR, 

                     "Only primitive types supported in the mapping. Not " + ret,

                     where

                 );

             }

         }

         return ret;

     }

     private static String findBoxedType(String ret) {

         if (ret.equals("boolean")) {

             return Boolean.class.getName();

         }

         if (ret.equals("byte")) {

             return Byte.class.getName();

         }

         if (ret.equals("short")) {

             return Short.class.getName();

         }

         if (ret.equals("char")) {

             return Character.class.getName();

         }

         if (ret.equals("int")) {

             return Integer.class.getName();

         }

         if (ret.equals("long")) {

             return Long.class.getName();

         }

         if (ret.equals("float")) {

             return Float.class.getName();

         }

         if (ret.equals("double")) {

             return Double.class.getName();

         }

         return null;

     }

     private boolean verifyPropName(Element e, String propName, Property[] existingProps) {

         StringBuilder sb = new StringBuilder();

         String sep = "";

         for (Property property : existingProps) {

             if (property.name().equals(propName)) {

                 return true;

             }

             sb.append(sep);

             sb.append('"');

             sb.append(property.name());

             sb.append('"');

             sep = ", ";

         }

         err().printMessage(Diagnostic.Kind.ERROR,

             propName + " is not one of known properties: " + sb

             , e

         );

         return false;

     }

     private static String findPkgName(Element e) {

         for (;;) {

             if (e.getKind() == ElementKind.PACKAGE) {

                 return ((PackageElement)e).getQualifiedName().toString();

             }

             e = e.getEnclosingElement();

         }

     }

     private boolean generateFunctions(

         Element clazz, StringWriter body, String className, 

         List<? extends Element> enclosedElements, List<String> functions

     ) {

         for (Element m : enclosedElements) {

             if (m.getKind() != ElementKind.METHOD) {

                 continue;

             }

             ExecutableElement e = (ExecutableElement)m;

             OnFunction onF = e.getAnnotation(OnFunction.class);

             if (onF == null) {

                 continue;

             }

             if (!e.getModifiers().contains(Modifier.STATIC)) {

                 err().printMessage(

                     Diagnostic.Kind.ERROR, "@OnFunction method needs to be static", e

                 );

                 return false;

             }

             if (e.getModifiers().contains(Modifier.PRIVATE)) {

                 err().printMessage(

                     Diagnostic.Kind.ERROR, "@OnFunction method cannot be private", e

                 );

                 return false;

             }

             if (e.getReturnType().getKind() != TypeKind.VOID) {

                 err().printMessage(

                     Diagnostic.Kind.ERROR, "@OnFunction method should return void", e

                 );

                 return false;

             }

             String n = e.getSimpleName().toString();

             body.append("private void ").append(n).append("(Object data, Object ev) {\n");

             body.append("  ").append(clazz.getSimpleName()).append(".").append(n).append("(");

             body.append(wrapParams(e, null, className, "ev", "data"));

             body.append(");\n");

             body.append("}\n");

             functions.add(n);

             functions.add(n + "__VLjava_lang_Object_2Ljava_lang_Object_2");

         }

         return true;

     }

     private boolean generateReceive(

         Element clazz, StringWriter body, String className, 

         List<? extends Element> enclosedElements, List<String> functions

     ) {

         for (Element m : enclosedElements) {

             if (m.getKind() != ElementKind.METHOD) {

                 continue;

             }

             ExecutableElement e = (ExecutableElement)m;

             OnReceive onR = e.getAnnotation(OnReceive.class);

             if (onR == null) {

                 continue;

             }

             if (!e.getModifiers().contains(Modifier.STATIC)) {

                 err().printMessage(

                     Diagnostic.Kind.ERROR, "@OnReceive method needs to be static", e

                 );

                 return false;

             }

             if (e.getModifiers().contains(Modifier.PRIVATE)) {

                 err().printMessage(

                     Diagnostic.Kind.ERROR, "@OnReceive method cannot be private", e

                 );

                 return false;

             }

             if (e.getReturnType().getKind() != TypeKind.VOID) {

                 err().printMessage(

                     Diagnostic.Kind.ERROR, "@OnReceive method should return void", e

                 );

                 return false;

             }

             String modelClass = null;

             boolean expectsList = false;

             List<String> args = new ArrayList<>();

             {

                 for (VariableElement ve : e.getParameters()) {

                     TypeMirror modelType = null;

                     if (ve.asType().toString().equals(className)) {

                         args.add(className + ".this");

                     } else if (isModel(ve.asType())) {

                         modelType = ve.asType();

                     } else if (ve.asType().getKind() == TypeKind.ARRAY) {

                         modelType = ((ArrayType)ve.asType()).getComponentType();

                         expectsList = true;

                     }

                     if (modelType != null) {

                         if (modelClass != null) {

                             err().printMessage(Diagnostic.Kind.ERROR, "There can be only one model class among arguments", e);

                         } else {

                             modelClass = modelType.toString();

                             if (expectsList) {

                                 args.add("arr");

                             } else {

                                 args.add("arr[0]");

                             }

                         }

                     }

                 }

             }

             if (modelClass == null) {

                 err().printMessage(Diagnostic.Kind.ERROR, "The method needs to have one @Model class as parameter", e);

             }

             String n = e.getSimpleName().toString();

             body.append("public void ").append(n).append("(");

             StringBuilder assembleURL = new StringBuilder();

             {

                 String sep = "";

                 for (String p : findParamNames(e, onR.url(), assembleURL)) {

                     body.append(sep);

                     body.append("String ").append(p);

                     sep = ", ";

                 }

             }

             body.append(") {\n");

             body.append("  final Object[] result = { null };\n");

             body.append(

                 "  class ProcessResult implements Runnable {\n" +

                 "    @Override\n" +

                 "    public void run() {\n" +

                 "      Object value = result[0];\n");

             body.append(

                 "      " + modelClass + "[] arr;\n");

             body.append(

                 "      if (value instanceof Object[]) {\n" +

                 "        Object[] data = ((Object[])value);\n" +

                 "        arr = new " + modelClass + "[data.length];\n" +

                 "        for (int i = 0; i < data.length; i++) {\n" +

                 "          arr[i] = new " + modelClass + "(data[i]);\n" +

                 "        }\n" +

                 "      } else {\n" +

                 "        arr = new " + modelClass + "[1];\n" +

                 "        arr[0] = new " + modelClass + "(value);\n" +

                 "      }\n"

             );

             {

                 body.append(clazz.getSimpleName()).append(".").append(n).append("(");

                 String sep = "";

                 for (String arg : args) {

                     body.append(sep);

                     body.append(arg);

                     sep = ", ";

                 }

                 body.append(");\n");

             }

             body.append(

                 "    }\n" +

                 "  }\n"

             );

             body.append("  org.apidesign.bck2brwsr.htmlpage.ConvertTypes.loadJSON(\n      ");

             body.append(assembleURL);

             body.append(", result, new ProcessResult()\n  );\n");

 //            body.append("  ").append(clazz.getSimpleName()).append(".").append(n).append("(");

 //            body.append(wrapParams(e, null, className, "ev", "data"));

 //            body.append(");\n");

             body.append("}\n");

         }

         return true;

     }

     private CharSequence wrapParams(

         ExecutableElement ee, String id, String className, String evName, String dataName

     ) {

         TypeMirror stringType = processingEnv.getElementUtils().getTypeElement("java.lang.String").asType();

         StringBuilder params = new StringBuilder();

         boolean first = true;

         for (VariableElement ve : ee.getParameters()) {

             if (!first) {

                 params.append(", ");

             }

             first = false;

             String toCall = null;

             if (ve.asType() == stringType) {

                 if (ve.getSimpleName().contentEquals("id")) {

                     params.append('"').append(id).append('"');

                     continue;

                 }

                 toCall = "org.apidesign.bck2brwsr.htmlpage.ConvertTypes.toString(";

             }

             if (ve.asType().getKind() == TypeKind.DOUBLE) {

                 toCall = "org.apidesign.bck2brwsr.htmlpage.ConvertTypes.toDouble(";

             }

             if (ve.asType().getKind() == TypeKind.INT) {

                 toCall = "org.apidesign.bck2brwsr.htmlpage.ConvertTypes.toInt(";

             }

             if (dataName != null && ve.getSimpleName().contentEquals(dataName) && isModel(ve.asType())) {

                 toCall = "org.apidesign.bck2brwsr.htmlpage.ConvertTypes.toModel(" + ve.asType() + ".class, ";

             }

             if (toCall != null) {

                 params.append(toCall);

                 if (dataName != null && ve.getSimpleName().contentEquals(dataName)) {

                     params.append(dataName);

                     params.append(", null");

                 } else {

                     params.append(evName);

                     params.append(", \"");

                     params.append(ve.getSimpleName().toString());

                     params.append("\"");

                 }

                 params.append(")");

                 continue;

             }

             String rn = fqn(ve.asType(), ee);

             int last = rn.lastIndexOf('.');

             if (last >= 0) {

                 rn = rn.substring(last + 1);

             }

             if (rn.equals(className)) {

                 params.append(className).append(".this");

                 continue;

             }

             err().printMessage(Diagnostic.Kind.ERROR, 

                 "@On method can only accept String named 'id' or " + className + " arguments",

                 ee

             );

         }

         return params;

     }

     private boolean isModel(TypeMirror tm) {

         final Element e = processingEnv.getTypeUtils().asElement(tm);

         if (e == null) {

             return false;

         }

         for (Element ch : e.getEnclosedElements()) {

             if (ch.getKind() == ElementKind.METHOD) {

                 ExecutableElement ee = (ExecutableElement)ch;

                 if (ee.getParameters().isEmpty() && ee.getSimpleName().contentEquals("modelFor")) {

                     return true;

                 }

             }

         }

         return models.values().contains(e.getSimpleName().toString());

     }

     private void writeStringArray(List<String> strings, Writer w) throws IOException {

         w.write("new String[] {\n");

         String sep = "";

         for (String n : strings) {

             w.write(sep);

             if (n == null) {

                 w.write("    null");

             } else {

                 w.write("    \"" + n + "\"");

             }

             sep = ",\n";

         }

         w.write("\n  }");

     }

     private void writeToString(Property[] props, Writer w) throws IOException {

         w.write("  public String toString() {\n");

         w.write("    StringBuilder sb = new StringBuilder();\n");

         w.write("    sb.append('{');\n");

         String sep = "";

         for (Property p : props) {

             w.write(sep);

             w.append("    sb.append(\"" + p.name() + ": \");\n");

             w.append("    sb.append(org.apidesign.bck2brwsr.htmlpage.ConvertTypes.toJSON(prop_");

             w.append(p.name()).append("));\n");

             sep =    "    sb.append(',');\n";

         }

         w.write("    sb.append('}');\n");

         w.write("    return sb.toString();\n");

         w.write("  }\n");

     }

     private void writeClone(String className, Property[] props, Writer w) throws IOException {

         w.write("  public " + className + " clone() {\n");

         w.write("    " + className + " ret = new " + className + "();\n");

         for (Property p : props) {

             if (!p.array()) {

                 boolean isModel[] = { false };

                 boolean isEnum[] = { false };

                 checkType(p, isModel, isEnum);

                 if (!isModel[0]) {

                     w.write("    ret.prop_" + p.name() + " = prop_" + p.name() + ";\n");

                     continue;

                 }

             }

             w.write("    ret.prop_" + p.name() + " = prop_" + p.name() + ".clone();\n");

         }

         w.write("    return ret;\n");

         w.write("  }\n");

     }

     private String inPckName(Element e) {

         StringBuilder sb = new StringBuilder();

         while (e.getKind() != ElementKind.PACKAGE) {

             if (sb.length() == 0) {

                 sb.append(e.getSimpleName());

             } else {

                 sb.insert(0, '.');

                 sb.insert(0, e.getSimpleName());

             }

             e = e.getEnclosingElement();

         }

         return sb.toString();

     }

     private String fqn(TypeMirror pt, Element relative) {

         if (pt.getKind() == TypeKind.ERROR) {

             final Elements eu = processingEnv.getElementUtils();

             PackageElement pckg = eu.getPackageOf(relative);

             return pckg.getQualifiedName() + "." + pt.toString();

         }

         return pt.toString();

     }

     private String checkType(Property p, boolean[] isModel, boolean[] isEnum) {

         String ret;

         try {

             ret = p.type().getName();

         } catch (MirroredTypeException ex) {

             TypeMirror tm = processingEnv.getTypeUtils().erasure(ex.getTypeMirror());

             final Element e = processingEnv.getTypeUtils().asElement(tm);

             final Model m = e == null ? null : e.getAnnotation(Model.class);

             if (m != null) {

                 ret = findPkgName(e) + '.' + m.className();

                 isModel[0] = true;

                 models.put(e, m.className());

             } else {

                 ret = tm.toString();

             }

             TypeMirror enm = processingEnv.getElementUtils().getTypeElement("java.lang.Enum").asType();

             enm = processingEnv.getTypeUtils().erasure(enm);

             isEnum[0] = processingEnv.getTypeUtils().isSubtype(tm, enm);

         }

         return ret;

     }

     private Iterable<String> findParamNames(Element e, String url, StringBuilder assembleURL) {

         List<String> params = new ArrayList<>();

         for (int pos = 0; ;) {

             int next = url.indexOf('{', pos);

             if (next == -1) {

                 assembleURL.append('"')

                     .append(url.substring(pos))

                     .append('"');

                 return params;

             }

             int close = url.indexOf('}', next);

             if (close == -1) {

                 err().printMessage(Diagnostic.Kind.ERROR, "Unbalanced '{' and '}' in " + url, e);

                 return params;

             }

             final String paramName = url.substring(next + 1, close);

             params.add(paramName);

             assembleURL.append('"')

                 .append(url.substring(pos, next))

                 .append("\" + ").append(paramName).append(" + ");

             pos = close + 1;

         }

     }

 }