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 package org.apidesign.html.context.spi;

 import net.java.html.BrwsrCtx;

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

 /** Factory class to assign various technologies 

  * to a {@link BrwsrCtx browser context}. Start with {@link #newBuilder()}

  * and then assign technologies with {@link Builder#register(java.lang.Class, java.lang.Object, int)}

  * method.

  *

  * @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>

  */

 public final class Contexts {

     private Contexts() {

     }

     /** Creates new, empty builder for creation of {@link BrwsrCtx}. At the

      * end call the {@link Builder#build()} method to generate the context.

      *

      * @return new instance of the builder

      */

     public static Builder newBuilder() {

         return new Builder();

     }

     /** Seeks for the specified technology in the provided context.

      * 

      * @param <Tech> type of the technology

      * @param context the context to seek in 

      *    (previously filled with ({@link Builder#register(java.lang.Class, java.lang.Object, int)})

      * @param technology class that identifies the technology

      * @return the technology in the context or <code>null</code>

      */

     public static <Tech> Tech find(BrwsrCtx context, Class<Tech> technology) {

         return CtxImpl.find(context, technology);

     }

     /** Implementors of various HTML technologies should

      * register their implementation via {@link java.util.ServiceProvider} so

      * {@link java.util.ServiceProvider} can find them, when their JARs are included

      * on the classpath of the running application.

      *

      * @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>

      */

     public static interface Provider {

         /** Register into the context if suitable technology is

          * available for the requesting class.

          * The provider should check if its own technology is available in current

          * scope (e.g. proper JDK, proper browser, etc.). The provider

          * can also find the right context depending on requestor's classloader, etc.

          * <p>

          * Providers should use {@link Builder} to enrich appropriately

          * the context.

          *

          * @param context the context builder to fill with technologies

          * @param requestor the application class requesting access the the HTML page

          * @see BrwsrCtx#findDefault(java.lang.Class)

          */

         void fillContext(Builder context, Class<?> requestor);

     }

     /** Support for providers of new {@link BrwsrCtx}. Providers of different

      * technologies should be of particular interest in this class. End users

      * designing their application with existing technologies should rather

      * point their attention to {@link BrwsrCtx} and co.

      *

      * @author Jaroslav Tulach <jtulach@netbeans.org>

      */

     public static final class Builder {

         private final CtxImpl impl = new CtxImpl();

         Builder() {

         }

         /** Registers new technology into the context. Each technology is

          * exactly identified by its implementation class and can be associated

          * with (positive) priority. In case of presence of multiple technologies

          * with the same class, the one with higher lower priority takes precedence.

          * @param <Tech> type of technology to register

          * @param type the real class of the technology type

          * @param impl an instance of the technology class

          * @param position the lower position, the more important implementation 

          *    which will be consulted sooner when seeking for a {@link Contexts#find(net.java.html.BrwsrCtx, java.lang.Class)}

          *    an implementation

          * @return this builder

          */

         public <Tech> Builder register(Class<Tech> type, Tech impl, int position) {

             if (position <= 0) {

                 throw new IllegalStateException();

             }

             this.impl.register(type, impl, position);

             return this;

         }

         /** Generates context based on values previously inserted into

          * this builder.

          *

          * @return new, immutable instance of {@link BrwsrCtx}

          */

         public BrwsrCtx build() {

             return impl.build();

         }

     }

 }