/*******************************************************************************
 * Copyright (c) 2007, 2016 BMW Car IT, Technische Universitaet Muenchen, 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:
 * Johannes Faltermeier - Initial API and implementation
 *******************************************************************************/
package org.eclipse.emf.edapt.internal.migration.internal;

import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;

import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.eclipse.emf.ecore.EFactory;
import org.eclipse.emf.ecore.EPackage;
import org.eclipse.emf.edapt.spi.migration.MigrationPlugin;
import org.osgi.framework.Bundle;

/**
 * Helper class for reading custom {@link EFactory EFactories} from the extension point.
 *
 * @author jfaltermeier
 *
 */
public final class FactoryHelper {

	/**
	 * The instance.
	 */
	public static final FactoryHelper INSTANCE = new FactoryHelper();

	private static final String CLASS = "class"; //$NON-NLS-1$
	private static final String NS_URI = "nsURI"; //$NON-NLS-1$
	private static final String USE_WILDCARDS = "useWildcards"; //$NON-NLS-1$
	private static final String POINT_ID = "org.eclipse.emf.edapt.factories"; //$NON-NLS-1$

	private final Map<String, Class<? extends EFactory>> nsURIToFactoryMap;
	private final Map<String, Boolean> wildcardsUsageMap;

	private FactoryHelper() {
		nsURIToFactoryMap = new LinkedHashMap<String, Class<? extends EFactory>>();
		wildcardsUsageMap = new HashMap<String, Boolean>();
		readExtensionPoint();
	}

	private void readExtensionPoint() {
		final IExtensionRegistry extensionRegistry = Platform
			.getExtensionRegistry();
		if (extensionRegistry == null) {
			return;
		}
		final IConfigurationElement[] configurationElements = extensionRegistry
			.getConfigurationElementsFor(POINT_ID);
		for (final IConfigurationElement configurationElement : configurationElements) {
			registerFactory(configurationElement);
		}
	}

	private void registerFactory(IConfigurationElement configurationElement) {
		try {
			final String nsURI = configurationElement.getAttribute(NS_URI);
			final String bundle = configurationElement.getContributor().getName();
			final String className = configurationElement.getAttribute(CLASS);
			final Class<? extends EFactory> clazz = loadClass(bundle, className);
			if (nsURI == null || clazz == null) {
				return;
			}
			final boolean useWildcards = Boolean.parseBoolean(configurationElement.getAttribute(USE_WILDCARDS));
			nsURIToFactoryMap.put(nsURI, clazz);
			wildcardsUsageMap.put(nsURI, useWildcards);
		} catch (final ClassNotFoundException e) {
			MigrationPlugin.INSTANCE.log(e);
		}

	}

	@SuppressWarnings("unchecked")
	private static Class<? extends EFactory> loadClass(String bundleName,
		String clazz) throws ClassNotFoundException {
		final Bundle bundle = Platform.getBundle(bundleName);
		if (bundle == null) {
			MigrationPlugin.INSTANCE.log("Could not get bundle " + bundleName + " from platform."); //$NON-NLS-1$ //$NON-NLS-2$
		}
		return (Class<? extends EFactory>) bundle.loadClass(clazz);
	}

	/**
	 * Overrides the {@link EFactory} for the given {@link EPackage} if a custom EFactory
	 * was registered for the factory's nsURI.
	 *
	 * @param ePackage the package
	 */
	public void overrideFactory(EPackage ePackage) {
		try {
			final Class<? extends EFactory> clazz = getEFactoryFromMap(ePackage.getNsURI());
			if (clazz == null) {
				return;
			}
			final EFactory eFactory = clazz.getConstructor().newInstance();
			ePackage.setEFactoryInstance(eFactory);
		} catch (final InstantiationException e) {
			MigrationPlugin.INSTANCE.log(e);
		} catch (final IllegalAccessException e) {
			MigrationPlugin.INSTANCE.log(e);
		} catch (final IllegalArgumentException e) {
			MigrationPlugin.INSTANCE.log(e);
		} catch (final InvocationTargetException e) {
			MigrationPlugin.INSTANCE.log(e);
		} catch (final NoSuchMethodException e) {
			MigrationPlugin.INSTANCE.log(e);
		} catch (final SecurityException e) {
			MigrationPlugin.INSTANCE.log(e);
		}
	}

	/**
	 * Returns the {@link EFactory} registered for the given nsURI, taking wildcards into account, if such a factory
	 * exists.
	 *
	 * @param nsURI
	 * @return if there exists a factory registered for a matching nsURI, without any wildcards, it will be returned
	 *         first. Otherwise, the method will return the first factory that it can match (using wildcards) to the
	 *         given nsURI
	 *         May return null.
	 */
	private Class<? extends EFactory> getEFactoryFromMap(String nsURI) {
		if (nsURI == null) {
			return null;
		}
		// if we have an exact match, that doesn't use wildcards, return the value from the factory map
		if (wildcardsUsageMap.get(nsURI) != null && !wildcardsUsageMap.get(nsURI)) {
			return nsURIToFactoryMap.get(nsURI);
		}
		// else, search if we can find a match using wildcards
		// if multiple matches exist, the first one will be returned
		for (final String uri : wildcardsUsageMap.keySet()) {
			if (wildcardsUsageMap.get(uri) && nsURI.matches(uri.replace("*", ".*"))) { //$NON-NLS-1$ //$NON-NLS-2$
				return nsURIToFactoryMap.get(uri);
			}
		}
		// fallback to factory map
		return nsURIToFactoryMap.get(nsURI);
	}
}