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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

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 * The contents of this file are subject to the terms of either the GNU

 * General Public License Version 2 only ("GPL") or the Common

 * Development and Distribution License("CDDL") (collectively, the

 * "License"). You may not use this file except in compliance with the

 * License. You can obtain a copy of the License at

 * http://www.netbeans.org/cddl-gplv2.html

 * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the

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 * particular file as subject to the "Classpath" exception as provided

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 *

 * The Original Software is NetBeans. The Initial Developer of the Original

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 * If you wish your version of this file to be governed by only the CDDL

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 */

package net.java.html.boot.script;

import java.io.Reader;

import java.net.URL;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.logging.Level;

import java.util.logging.Logger;

import javax.script.Invocable;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

import org.apidesign.html.boot.spi.Fn;

import org.apidesign.html.boot.spi.Fn.Presenter;

/** Implementation of {@link Presenter} that delegates

 * to Java {@link ScriptEngine scripting} API. The presenter runs headless

 * without appropriate simulation of browser APIs. Its primary usefulness

 * is inside testing environments. 

 * <p>

 * One can load in browser simulation for example from 

 * <a href="http://www.envjs.com/">env.js</a>. The best way to achieve so,

 * is to add dependency on XXX

 * 

 *

 * @author Jaroslav Tulach

 */

public final class ScriptPresenter implements Presenter, Fn.FromJavaScript, Fn.ToJavaScript {

    private final ScriptEngine eng;

    public ScriptPresenter() {

        try {

            eng = new ScriptEngineManager().getEngineByName("javascript");

            eng.eval("function alert(msg) { Packages.java.lang.System.out.println(msg); };");

        } catch (ScriptException ex) {

            throw new IllegalStateException(ex);

        }

    }

    @Override

    public Fn defineFn(String code, String... names) {

        return defineImpl(code, names);

    }

    private FnImpl defineImpl(String code, String... names) {

        StringBuilder sb = new StringBuilder();

        sb.append("(function() {");

        sb.append("  return function(");

        String sep = "";

        if (names != null) for (String n : names) {

            sb.append(sep).append(n);

            sep = ",";

        }

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

        sb.append(code);

        sb.append("};");

        sb.append("})()");

        final Object fn;

        try {

            fn = eng.eval(sb.toString());

        } catch (ScriptException ex) {

            throw new IllegalStateException(ex);

        }

        return new FnImpl(this, fn);

    }

    @Override

    public void displayPage(URL page, Runnable onPageLoad) {

        // not really displaying anything

        if (onPageLoad != null) {

            onPageLoad.run();

        }

    }

    @Override

    public void loadScript(Reader code) throws Exception {

        eng.eval(code);

    }

    //

    // array conversions

    //

    final Object convertArrays(Object[] arr) throws Exception {

        for (int i = 0; i < arr.length; i++) {

            if (arr[i] instanceof Object[]) {

                arr[i] = convertArrays((Object[]) arr[i]);

            }

        }

        final Object wrapArr = wrapArrFn().invokeImpl(null, false, arr); // NOI18N

        return wrapArr;

    }

    private FnImpl wrapArrImpl;

    private FnImpl wrapArrFn() {

        if (wrapArrImpl == null) {

            try {

                wrapArrImpl = defineImpl("return Array.prototype.slice.call(arguments);");

            } catch (Exception ex) {

                throw new IllegalStateException(ex);

            }

        }

        return wrapArrImpl;

    }

    final Object checkArray(Object val) throws Exception {

        final FnImpl fn = arraySizeFn();

        final Object fnRes = fn.invokeImpl(null, false, val, null);

        int length = ((Number) fnRes).intValue();

        if (length == -1) {

            return val;

        }

        Object[] arr = new Object[length];

        fn.invokeImpl(null, false, val, arr);

        return arr;

    }

    private FnImpl arraySize;

    private FnImpl arraySizeFn() {

        if (arraySize == null) {

            try {

                arraySize = defineImpl("\n"

                    + "if (to === null) {\n"

                    + "  if (Object.prototype.toString.call(arr) === '[object Array]') return arr.length;\n"

                    + "  else return -1;\n"

                    + "} else {\n"

                    + "  var l = arr.length;\n"

                    + "  for (var i = 0; i < l; i++) to[i] = arr[i];\n"

                    + "  return l;\n"

                    + "}", "arr", "to"

                );

            } catch (Exception ex) {

                throw new IllegalStateException(ex);

            }

        }

        return arraySize;

    }

    @Override

    public Object toJava(Object jsArray) {

        try {

            return checkArray(jsArray);

        } catch (Exception ex) {

            throw new IllegalStateException(ex);

        }

    }

    @Override

    public Object toJavaScript(Object toReturn) {

        if (toReturn instanceof Object[]) {

            try {

                return convertArrays((Object[])toReturn);

            } catch (Exception ex) {

                throw new IllegalStateException(ex);

            }

        } else {

            return toReturn;

        }

    }

    private class FnImpl extends Fn {

        private final Object fn;

        public FnImpl(Presenter presenter, Object fn) {

            super(presenter);

            this.fn = fn;

        }

        @Override

        public Object invoke(Object thiz, Object... args) throws Exception {

            return invokeImpl(thiz, true, args);

        }

            final Object invokeImpl(Object thiz, boolean arrayChecks, Object... args) throws Exception {

                List<Object> all = new ArrayList<Object>(args.length + 1);

                all.add(thiz == null ? fn : thiz);

                for (int i = 0; i < args.length; i++) {

                    if (arrayChecks) {

                        if (args[i] instanceof Object[]) {

                            Object[] arr = (Object[]) args[i];

                            Object conv = ((ScriptPresenter)presenter()).convertArrays(arr);

                            args[i] = conv;

                        }

                        if (args[i] instanceof Character) {

                            args[i] = (int)((Character)args[i]);

                        }

                    }

                    all.add(args[i]);

                }

                Object ret = ((Invocable)eng).invokeMethod(fn, "call", all.toArray()); // NOI18N

                if (ret == fn) {

                    return null;

                }

                if (!arrayChecks) {

                    return ret;

                }

                return ((ScriptPresenter)presenter()).checkArray(ret);

            }

    }

}