/**

 * 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.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.MirroredTypeException;

import javax.lang.model.type.TypeKind;

import javax.lang.model.type.TypeMirror;

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.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.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 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();

        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(" {\n");

                w.append("  private Object json;\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<" + e.getSimpleName() + "> modelFor() { return null; }\n");

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

            } finally {

                w.close();

            }

        } catch (IOException ex) {

            processingEnv.getMessager().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) {

            processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR, "Can't read " + p.xhtml(), 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;

            }

            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 {

                    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) {

            processingEnv.getMessager().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) {

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

                            ok = false;

                            continue;

                        }

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

                            processingEnv.getMessager().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)) {

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

                            ok = false;

                            continue;

                        }

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

                            processingEnv.getMessager().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 = ert.toString();

            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 = pe.asType().toString();

                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;

        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 = 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 = processingEnv.getTypeUtils().isSubtype(tm, enm);

        }

        if (p.array()) {

            String bt = findBoxedType(ret);

            if (bt != null) {

                return bt;

            }

        }

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

            String bt = findBoxedType(ret);

            if (bt == null) {

                processingEnv.getMessager().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 = ", ";

        }

        processingEnv.getMessager().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)) {

                processingEnv.getMessager().printMessage(

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

                );

                return false;

            }

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

                processingEnv.getMessager().printMessage(

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

                );

                return false;

            }

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

                processingEnv.getMessager().printMessage(

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

                );

                return false;

            }

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

            body.append("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 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 = ve.asType().toString();

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

            if (last >= 0) {

                rn = rn.substring(last + 1);

            }

            if (rn.equals(className)) {

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

                continue;

            }

            processingEnv.getMessager().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  }");

    }

}