org.eclipse.virgo.ide.bundlor.core/src/org/eclipse/virgo/ide/bundlor/internal/core/IncrementalPartialManifestManager.java

/*******************************************************************************
 * Copyright (c) 2009, 2012 SpringSource, a divison of VMware, Inc.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     SpringSource, a division of VMware, Inc. - initial API and implementation
 *******************************************************************************/

package org.eclipse.virgo.ide.bundlor.internal.core;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.eclipse.jdt.core.IJavaProject;
import org.eclipse.virgo.bundlor.support.partialmanifest.ReadablePartialManifest;

/**
 * Manages the {@link IncrementalReadablePartialManifest} instances by {@link IJavaProject}.
 *
 * @author Christian Dupuis
 * @since 1.1.2
 */
public class IncrementalPartialManifestManager {

    /**
     * Internal read write lock to protect the read and write operations of the internal caches
     */
    private final ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();

    /** Write lock to protect the model from concurrent write operations */
    private final Lock w = this.rwl.writeLock();

    /** Read lock to protect from reading while writing to the model resources */
    private final Lock r = this.rwl.readLock();

    /**
     * Internal structure to associate {@link IncrementalReadablePartialManifest}s to {@link IJavaProject}s
     */
    private final Map<IJavaProject, ReadablePartialManifest> manifests = new ConcurrentHashMap<IJavaProject, ReadablePartialManifest>();

    /**
     * Internal structure to associate {@link IncrementalReadablePartialManifest}s that represent the test manifests to
     * {@link IJavaProject}s
     */
    private final Map<IJavaProject, ReadablePartialManifest> testManifests = new ConcurrentHashMap<IJavaProject, ReadablePartialManifest>();

    /**
     * Returns an instance of {@link IncrementalReadablePartialManifest} for the given {@link IJavaProject}.
     */
    public ReadablePartialManifest getPartialManifest(IJavaProject javaProject, boolean isTestManifest, boolean createNew) {
        if (!createNew) {
            try {
                this.r.lock();
                if (!isTestManifest) {
                    if (this.manifests.containsKey(javaProject)) {
                        return this.manifests.get(javaProject);
                    }
                } else {
                    if (this.testManifests.containsKey(javaProject)) {
                        return this.testManifests.get(javaProject);
                    }
                }
            } finally {
                this.r.unlock();
            }
        }
        try {
            this.w.lock();
            ReadablePartialManifest manifest = new IncrementalReadablePartialManifest();
            if (!isTestManifest) {
                this.manifests.put(javaProject, manifest);
            } else {
                this.testManifests.put(javaProject, manifest);
            }
            return manifest;
        } finally {
            this.w.unlock();
        }
    }

    /**
     * Returns <code>true</code> if the given {@link IJavaProject} has {@link IncrementalReadablePartialManifest}
     * associated with it.
     */
    public boolean hasPartialManifest(IJavaProject javaProject) {
        try {
            this.r.lock();
            return this.manifests.containsKey(javaProject);
        } finally {
            this.r.unlock();
        }
    }

    /**
     * Clears out existing manifest models.
     * <p>
     * Used form the UI to trigger a clean model creation on the next run.
     */
    public void clearPartialManifest(IJavaProject javaProject) {
        try {
            this.w.lock();
            this.manifests.remove(javaProject);
            this.testManifests.remove(javaProject);
        } finally {
            this.w.unlock();
        }
    }

}