/*******************************************************************************
 * Copyright (c) 2001, 2004 IBM Corporation and others.
 * 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:
 *     IBM Corporation - initial API and implementation
 *     Jens Lukowski/Innoopract - initial renaming/restructuring
 *     
 *******************************************************************************/
package org.eclipse.wst.sse.ui.registry;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.wst.sse.ui.Logger;


public class AdapterFactoryRegistryImpl implements AdapterFactoryRegistry, AdapterFactoryRegistryExtension {

	protected final static String ATT_CLASS = "class"; //$NON-NLS-1$

	private static AdapterFactoryRegistry instance = null;

	static synchronized public AdapterFactoryRegistry getInstance() {
		if (instance == null) {
			instance = new AdapterFactoryRegistryImpl();
		}
		return instance;
	}

	// this map exists so there is only one provider
	// instance not duplicate providers for different content types
	private HashMap adapterProviders = null;

	private boolean DEBUG = false;
	/**
	 * This HashMap contains: [contentTypeId -> element2providerMap] | V
	 * [configurationElement -> AdapterFactoryProvider]
	 *  
	 */
	private HashMap hashMap = null;

	// providers with no content type associated
	// just added through the add(...) method
	private HashSet unassociatedProviders = null;

	private AdapterFactoryRegistryImpl() {
		super();
		this.hashMap = new HashMap();
		this.unassociatedProviders = new HashSet();
		this.adapterProviders = new HashMap();

		// doesn't instantiate classes, just stores configuration elements
		AdapterFactoryRegistryReader.readRegistry(hashMap);
	}

	void add(AdapterFactoryProvider adapterFactoryProvider) {
		this.unassociatedProviders.add(adapterFactoryProvider);
	}

	public Iterator getAdapterFactories() {

		if (DEBUG) {
			System.out.println("====================================================================================");
			System.out.println("GETTING ALL ADAPTER FACTORIES");
		}

		List results = new ArrayList();

		// add providers that have no content type specification
		results.addAll(this.unassociatedProviders);
		Iterator it = this.hashMap.keySet().iterator();
		String contentTypeId = null;
		while (it.hasNext()) {
			contentTypeId = (String) it.next();

			if (DEBUG)
				System.out.println(" + for: " + contentTypeId);

			results.addAll(getAdapterFactoriesAsList(contentTypeId));
		}

		if (DEBUG) {
			System.out.println("====================================================================================");
		}

		return results.iterator();
	}

	public Iterator getAdapterFactories(String contentType) {

		if (DEBUG) {
			System.out.println("====================================================================================");
			System.out.println("GETTING ADAPTER FACTORIES for: " + contentType);
		}

		List results = new ArrayList();

		// add providers that have no content type specification
		results.addAll(unassociatedProviders);

		// add unknown content type providers (for backwards compatability)
		results.addAll(getAdapterFactoriesAsList(AdapterFactoryRegistryReader.UNKNOWN_CONTENT_TYPE));

		// add providers for specific content type
		results.addAll(getAdapterFactoriesAsList(contentType));

		if (DEBUG) {
			System.out.println("====================================================================================");
		}

		return results.iterator();
	}

	/**
	 * Using this new API, only AdapterFactoryProviders for a certain content
	 * type are instantiated. This will allow for the minimum number of
	 * plugins to be loaded rather than all that implement the adapter factory
	 * extension point.
	 * 
	 * @param contentType
	 * @return
	 */
	public List getAdapterFactoriesAsList(String contentType) {

		List results = new ArrayList();

		// get element2Provider map for specified content type
		Object o = hashMap.get(contentType);
		if (o != null) {

			// instantiate if necessary from element2adapterFactoryProvider
			// map
			HashMap element2Provider = (HashMap) o;
			Iterator it = element2Provider.keySet().iterator();
			IConfigurationElement element = null;
			String classname = null;
			Object existing = null;
			AdapterFactoryProvider p = null;
			while (it.hasNext()) {
				element = (IConfigurationElement) it.next();
				o = element2Provider.get(element);
				if (o != null) {
					// this provider has already been created
					if (DEBUG)
						System.out.println("already created: " + element.getAttribute(ATT_CLASS));

					results.add(o);
				} else {
					// need to create the provider
					try {
						classname = element.getAttribute(ATT_CLASS);

						if (DEBUG)
							System.out.println("about to create: " + classname);

						// check if we created one already
						existing = this.adapterProviders.get(classname);
						if (existing == null) {
							// this is the only place AdapterFactoryProviders
							// are created
							p = (AdapterFactoryProvider) element.createExecutableExtension(ATT_CLASS); // $NON-NLS-1$
							this.adapterProviders.put(classname, p);
						} else {
							p = (AdapterFactoryProvider) existing;
						}

						// add to element2Provider for this contentType
						element2Provider.put(element, p);
						// add to results to return for this method
						results.add(p);

					} catch (CoreException e) {
						// if the provider throws any exception, just log and
						// continue
						Logger.logException(e);
					}
				}
			}
		}
		return results;
	}
}