/**

  * 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;

 import java.util.concurrent.Executor;

 import java.util.logging.Logger;

 import org.netbeans.html.context.impl.CtxAccssr;

 import org.netbeans.html.context.impl.CtxImpl;

 import org.apidesign.html.context.spi.Contexts;

 /** Represents context where the <code>net.java.html.json.Model</code>

  * and other objects

  * operate in. The context is usually a particular HTML page in a browser.

  * The context is also associated with the actual HTML technology

  * in the HTML page - there is likely to be different context for 

  * <a href="http://knockoutjs.com">knockout.js</a> and different one

  * for <a href="http://angularjs.org">angular</a>.

  *

  * @author Jaroslav Tulach

  */

 public final class BrwsrCtx implements Executor {

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

     private final CtxImpl impl;

     private BrwsrCtx(CtxImpl impl) {

         this.impl = impl;

     }

     static {

         new CtxAccssr() {

             @Override

             protected BrwsrCtx newContext(CtxImpl impl) {

                 return new BrwsrCtx(impl);

             }

             @Override

             protected CtxImpl find(BrwsrCtx context) {

                 return context.impl;

             }

         };

     }

     /** Dummy context without binding to any real browser or technology. 

      * Useful for simple unit testing of behavior of various business logic

      * code.

      */

     public static final BrwsrCtx EMPTY = Contexts.newBuilder().build();

     /** currently {@link #execute(java.lang.Runnable) activated context} */

     private static final ThreadLocal<BrwsrCtx> CURRENT = new ThreadLocal<BrwsrCtx>();

     /** Seeks for the default context that is associated with the requesting

      * class. If no suitable context is found, a warning message is

      * printed and {@link #EMPTY} context is returned. One can enter 

      * a context by calling {@link #execute(java.lang.Runnable)}.

      * 

      * @param requestor the class that makes the request

      * @return appropriate context for the request

      */

     public static BrwsrCtx findDefault(Class<?> requestor) {

         BrwsrCtx brwsr = CURRENT.get();

         if (brwsr != null) {

             return brwsr;

         }

         org.apidesign.html.context.spi.Contexts.Builder cb = Contexts.newBuilder();

         boolean found = Contexts.fillInByProviders(requestor, cb);

         if (!found) {

             LOG.warning("No browser context found. Returning empty technology!");

             return EMPTY;

         }

         return cb.build();

     }

     /** 

      * <p>

      * Runs provided code in the context of this {@link BrwsrCtx}.

      * If there is an {@link Executor} {@link Contexts#find(net.java.html.BrwsrCtx, java.lang.Class)  registered in the context}

      * it is used to perform the given code. While the code <code>exec</code>

      * is running the value of {@link #findDefault(java.lang.Class)} returns

      * <code>this</code>. If the executor supports a single thread execution

      * policy, it may execute the runnable later (in such case this method

      * returns immediately). If the call to this method is done on the right

      * thread, the runnable should be executed synchronously.

      * </p>

      * <p>

      * <b>Example Using a Timer</b>

      * </p>

 <pre>

 <b>public final class</b> Periodicaly <b>extends</b> {@link java.util.TimerTask} {

     <b>private final</b> {@link BrwsrCtx} ctx;

     <b>private</b> Periodicaly(BrwsrCtx ctx) {

         // remember the browser context and use it later

         this.ctx = ctx;

     }

     <b>public void</b> run() {

         // arrives on wrong thread, needs to be re-scheduled

         ctx.{@link #execute(java.lang.Runnable) execute}(new Runnable() {

             <b>public void</b> run() {

                 // code that needs to run in a browser environment

             }

         });

     }

     // called when your page is ready

     <b>public static void</b> onPageLoad(String... args) <b>throws</b> Exception {

         // the context at the time of page initialization

         BrwsrCtx initialCtx = BrwsrCtx.findDefault(getClass());

         // the task that is associated with context 

         Periodicaly task = new Periodicaly(initialCtx);

         // creates a timer

         {@link java.util.Timer} t = new {@link java.util.Timer}("Move the box");

         // run the task ever 100ms

         t.{@link java.util.Timer#scheduleAtFixedRate(java.util.TimerTask, long, long) scheduleAtFixedRate}(task, 0, 100);

     }

 }

 </pre>    

      * 

      * @param exec the code to execute

      * @since 0.7.6

      */

     @Override public final void execute(final Runnable exec) {

         class Wrap implements Runnable {

             @Override

             public void run() {

                 BrwsrCtx prev = CURRENT.get();

                 try {

                     CURRENT.set(BrwsrCtx.this);

                     exec.run();

                 } finally {

                     CURRENT.set(prev);

                 }

             }

         }

         Wrap w = new Wrap();

         Executor runIn = Contexts.find(this, Executor.class);

         if (runIn == null) {

             w.run();

         } else {

             runIn.execute(w);

         }

     }

 }