/*

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

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package com.sun.tools.internal.xjc.reader;

import java.lang.reflect.Constructor;

import java.lang.reflect.InvocationTargetException;

import java.util.HashMap;

import java.util.Map;

import com.sun.tools.internal.xjc.ErrorReceiver;

import com.sun.tools.internal.xjc.model.Model;

/**

 * Holds all the binding related singleton components in a "ring",

 * and let you access those components, creating them as necessary.

 *

 * <p>

 * A {@link Ring} is local to a thread,

 * and only one instanceof {@link Ring} can be active at any given time.

 *

 * Use {@link #begin()} and {@link #end(Ring)} to start/end a ring scope.

 * Inside a scope, use {@link #get()} to obtain the instance.

 *

 * <p>

 * When a {@link Model} is built by the reader, an active {@link Ring} scope

 * is assumed.

 *

 *

 * <h2>Components in Ring</h2>

 * <p>

 * Depending on the schema language we are dealing with, different

 * components are in the model. But at least the following components

 * are in the ring.

 *

 * <ul>

 *  <li>{@link ErrorReceiver}

 * </ul>

 *

 * @author Kohsuke Kawaguchi

 */

public final class Ring {

    private final Map<Class,Object> components = new HashMap<Class,Object>();

    private static final ThreadLocal<Ring> instances = new ThreadLocal<Ring>();

    private Ring() {}

    public static <T> void add( Class<T> clazz, T instance ) {

        assert !get().components.containsKey(clazz);

        get().components.put(clazz,instance);

    }

    public static <T> void add( T o ) {

        add((Class<T>)o.getClass(),o);

    }

    public static <T> T get( Class<T> key ) {

        T t = (T)get().components.get(key);

        if(t==null) {

            try {

                Constructor<T> c = key.getDeclaredConstructor();

                c.setAccessible(true);

                t = c.newInstance();

                if(!get().components.containsKey(key))

                    // many components register themselves.

                    add(key,t);

            } catch (InstantiationException e) {

                throw new Error(e);

            } catch (IllegalAccessException e) {

                throw new Error(e);

            } catch (NoSuchMethodException e) {

                throw new Error(e);

            } catch (InvocationTargetException e) {

                throw new Error(e);

            }

        }

        assert t!=null;

        return t;

    }

    /**

     * A {@link Ring} instance is associated with a thread.

     */

    public static Ring get() {

        return instances.get();

    }

    /**

     * Starts a new scope.

     */

    public static Ring begin() {

        Ring r = null;

        synchronized (instances) {

            r = instances.get();

            instances.set(new Ring());

        }

        return r;

    }

    /**

     * Ends a scope.

     */

    public static void end(Ring old) {

        synchronized (instances) {

            instances.remove();

            instances.set(old);

        }

    }

}