package textbender.a.r.page; // Copyright 2007, Michael Allan.  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Textbender Software"), to deal in the Textbender Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicence, and/or sell copies of the Textbender Software, and to permit persons to whom the Textbender Software is furnished to do so, subject to the following conditions: The preceding copyright notice and this permission notice shall be included in all copies or substantial portions of the Textbender Software. THE TEXTBENDER SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE TEXTBENDER SOFTWARE OR THE USE OR OTHER DEALINGS IN THE TEXTBENDER SOFTWARE.

import java.util.concurrent.atomic.*;
import textbender.g.hold.*;
import textbender.g.lang.*;


/** Common to page daemons.
  * The single instance of PageDaemons is available via PageDaemons.i().
  * <p>
  *     Browser in-memory caching must be disabled.
  *     It <a href='http://reluk.ca/project/textbender/o/browser.xht#In-Memory-Caching-and-JSObject'
  *                                                                         >conflicts with JSObject</a>,
  *     which is used by the page daemon.
  *     Moreover, in-memory caching might retain dynamic markup
  *     across page visits, which would be inappropriate.
  *     We no longer attempt to clean that away, for each visit.
  *     </p>
  */
public @ThreadSafe final class PageDaemons
{


    /** The single instance of PageDaemons.
      */
    public static PageDaemons i() { return instanceA.get(); }


        private static final AtomicReference<PageDaemons> instanceA
            = new AtomicReference<PageDaemons>();



    /** Creates the single instance of PageDaemons,
      * and makes it available via {@linkplain #i() i}().
      */
    PageDaemons()
    {
        if( !instanceA.compareAndSet( /*expect*/null, PageDaemons.this )) throw new IllegalStateException();
    }



   // ------------------------------------------------------------------------------------


    /** Shared communication links.
      */
    public Connections connections() { return connections; }


        private final Connections connections = new Connections( Spool0.i() ); // no real spool possible, per Run



}