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

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 * 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

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

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

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

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 */

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);

        }

    }

}