/**

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

 *

 * Copyright 2013-2014 Oracle and/or its affiliates. All rights reserved.

 *

 * Oracle and Java are registered trademarks of Oracle and/or its affiliates.

 * Other names may be trademarks of their respective owners.

 *

 * 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

 * specific language governing permissions and limitations under the

 * License.  When distributing the software, include this License Header

 * Notice in each file and include the License file at

 * nbbuild/licenses/CDDL-GPL-2-CP.  Oracle designates this

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

 * by Oracle in the GPL Version 2 section of the License file that

 * accompanied this code. If applicable, add the following below the

 * License Header, with the fields enclosed by brackets [] replaced by

 * your own identifying information:

 * "Portions Copyrighted [year] [name of copyright owner]"

 *

 * Contributor(s):

 *

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

 * Software is Oracle. Portions Copyright 2013-2014 Oracle. All Rights Reserved.

 *

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

 * or only the GPL Version 2, indicate your decision by adding

 * "[Contributor] elects to include this software in this distribution

 * under the [CDDL or GPL Version 2] license." If you do not indicate a

 * single choice of license, a recipient has the option to distribute

 * your version of this file under either the CDDL, the GPL Version 2 or

 * to extend the choice of license to its licensees as provided above.

 * However, if you add GPL Version 2 code and therefore, elected the GPL

 * Version 2 license, then the option applies only if the new code is

 * made subject to such option by the copyright holder.

 */

package net.java.html.boot.script;

import java.io.Closeable;

import java.io.IOException;

import java.io.Reader;

import java.lang.ref.WeakReference;

import java.net.URL;

import java.util.ArrayList;

import java.util.List;

import java.util.concurrent.Executor;

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.netbeans.html.boot.spi.Fn;

import org.netbeans.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 wait until JDK-8046013 gets fixed....

 * 

 *

 * @author Jaroslav Tulach

 */

final class ScriptPresenter implements Fn.KeepAlive,

Presenter, Fn.FromJavaScript, Fn.ToJavaScript, Executor {

    private static final Logger LOG = Logger.getLogger(ScriptPresenter.class.getName());

    private final ScriptEngine eng;

    private final Executor exc;

    public ScriptPresenter(Executor exc) {

        this.exc = exc;

        try {

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

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

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

            eng.eval("function prompt(msg, txt) { Packages.java.lang.System.out.println(msg + ':' + txt); return txt; };");

        } catch (ScriptException ex) {

            throw new IllegalStateException(ex);

        }

    }

    @Override

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

        return defineImpl(code, names, null);

    }

    @Override

    public Fn defineFn(String code, String[] names, boolean[] keepAlive) {

        return defineImpl(code, names, keepAlive);

    }    

    private FnImpl defineImpl(String code, String[] names, boolean[] keepAlive) {

        StringBuilder sb = new StringBuilder();

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

        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("\n  };\n");

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

        final Object fn;

        try {

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

        } catch (ScriptException ex) {

            throw new IllegalStateException(ex);

        }

        return new FnImpl(this, fn, keepAlive);

    }

    @Override

    public void displayPage(URL page, Runnable onPageLoad) {

        try {

            eng.eval("if (typeof window !== 'undefined') window.location = '" + page + "'");

        } catch (ScriptException ex) {

            LOG.log(Level.SEVERE, "Cannot load " + page, ex);

        }

        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);", null, null);

            } 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"

                    + "}", new String[] { "arr", "to" }, null

                );

            } catch (Exception ex) {

                throw new IllegalStateException(ex);

            }

        }

        return arraySize;

    }

    @Override

    public Object toJava(Object jsArray) {

        if (jsArray instanceof Weak) {

            jsArray = ((Weak)jsArray).get();

        }

        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;

        }

    }

    @Override

    public void execute(final Runnable command) {

        if (Fn.activePresenter() == this) {

            command.run();

            return;

        }

        class Wrap implements Runnable {

            public void run() {

                try (Closeable c = Fn.activate(ScriptPresenter.this)) {

                    command.run();

                } catch (IOException ex) {

                    throw new IllegalStateException(ex);

                }

            }

        }

        final Runnable wrap = new Wrap();

        if (exc == null) {

            wrap.run();

        } else {

            exc.execute(wrap);

        }

    }

    private class FnImpl extends Fn {

        private final Object fn;

        private final boolean[] keepAlive;

        public FnImpl(Presenter presenter, Object fn, boolean[] keepAlive) {

            super(presenter);

            this.fn = fn;

            this.keepAlive = keepAlive;

        }

        @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<>(args.length + 1);

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

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

                    Object conv = args[i];

                    if (arrayChecks) {

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

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

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

                        }

                        if (conv != null && keepAlive != null

                            && !keepAlive[i] && !isJSReady(conv)

                            && !conv.getClass().getSimpleName().equals("$JsCallbacks$") // NOI18N

                            ) {

                            conv = new Weak(conv);

                        }

                        if (conv instanceof Character) {

                            conv = (int)(Character)conv;

                        }

                    }

                    all.add(conv);

                }

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

                if (ret instanceof Weak) {

                    ret = ((Weak)ret).get();

                }

                if (ret == fn) {

                    return null;

                }

                if (!arrayChecks) {

                    return ret;

                }

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

            }

    }

    private static boolean isJSReady(Object obj) {

        if (obj == null) {

            return true;

        }

        if (obj instanceof String) {

            return true;

        }

        if (obj instanceof Number) {

            return true;

        }

        final String cn = obj.getClass().getName();

        if (cn.startsWith("jdk.nashorn") || ( // NOI18N

            cn.contains(".mozilla.") && cn.contains(".Native") // NOI18N

        )) {

            return true;

        }

        if (obj instanceof Character) {

            return true;

        }

        return false;

    }    

    private static final class Weak extends WeakReference<Object> {

        public Weak(Object referent) {

            super(referent);

        }

    }

}