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

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

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

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

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 * 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

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 */

package org.netbeans.html.context.spi;

import java.lang.annotation.Documented;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

import java.util.HashSet;

import java.util.ServiceLoader;

import java.util.Set;

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

 */

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.

     * 

     * @param context instances of various classes or names of {@link Id technologies} 

     *    to be preferred and used in the built {@link BrwsrCtx context}.

     * @return new instance of the builder

     * @since 1.1

     */

    public static Builder newBuilder(Object... context) {

        return new Builder(context);

    }

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

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

     * Simply calls {@link #newBuilder(java.lang.Object...) newBuilder(new Object[0])}.

     * 

     * @return new instance of the builder

     */

    public static Builder newBuilder() {

        return newBuilder(new Object[0]);

    }

    /** 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);

    }

    /** Seeks {@link ServiceLoader} for all registered instances of

     * {@link Provider} and asks them to {@link Provider#fillContext(org.netbeans.html.context.spi.Contexts.Builder, java.lang.Class) fill

     * the builder}.

     * 

     * @param requestor the application class for which to find the context

     * @param cb the context builder to register technologies into

     * @return <code>true</code>, if some instances of the provider were

     *    found, <code>false</code> otherwise

     * @since 0.7.6

     */

    public static boolean fillInByProviders(Class<?> requestor, Contexts.Builder cb) {

        boolean found = false;

        ClassLoader l;

        try {

            l = requestor.getClassLoader();

        } catch (SecurityException ex) {

            l = null;

        }

        Set<Class<?>> classes = new HashSet<Class<?>>();

        for (Provider cp : ServiceLoader.load(Provider.class, l)) {

            if (!classes.add(cp.getClass())) {

                continue;

            }

            cp.fillContext(cb, requestor);

            found = true;

        }

        try {

            for (Provider cp : ServiceLoader.load(Provider.class, Provider.class.getClassLoader())) {

                if (!classes.add(cp.getClass())) {

                    continue;

                }

                cp.fillContext(cb, requestor);

                found = true;

            }

        } catch (SecurityException ex) {

            if (!found) {

                throw ex;

            }

        }

        if (!found) {

            for (Provider cp : ServiceLoader.load(Provider.class)) {

                if (!classes.add(cp.getClass())) {

                    continue;

                }

                cp.fillContext(cb, requestor);

                found = true;

            }

        }

        return found;

    }

    /** Identifies the technologies passed to {@link Builder context builder}

     * by a name. Each implementation of a technology 

     * {@link Builder#register(java.lang.Class, java.lang.Object, int) registered into a context}

     * can be annotated with a name (or multiple names). Such implementation

     * will later be 

     * {@link Contexts#fillInByProviders(java.lang.Class, org.netbeans.html.context.spi.Contexts.Builder)  preferred during lookup}

     * if their name(s) has been requested in when 

     * {@link Contexts#newBuilder(java.lang.Object...)  creating a context}.

     * @since 1.1

     */

    @Retention(RetentionPolicy.RUNTIME)

    @Target(ElementType.TYPE)

    @Documented

    public @interface Id {

        /** Identifier(s) for the implementation. 

         * 

         * @return one of more identifiers giving this implementation name(s)

         */

        public String[] value();

    }

    /** Implementors of various HTML technologies should

     * register their implementation via <code>org.openide.util.lookup.ServiceProvider</code>, so

     * {@link ServiceLoader} can find them, when their JARs are included

     * on the classpath of the running application.

     *

     * @author Jaroslav Tulach

     */

    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

     */

    public static final class Builder {

        private final CtxImpl impl;

        public Builder(Object[] context) {

            this.impl = new CtxImpl(context);

        }

        /** 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 (impl == null) {

                return this;

            }

            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();

        }

    }

}