/*
 * Copyright (c) 2003-2004 Christopher Lenz and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     Christopher Lenz - initial API and implementation
 * 
 * $Id: ProfileManager.java,v 1.1 2004-09-02 18:07:11 jsurfer Exp $
 */

package net.sourceforge.phpeclipse.css.core.internal.profiles;

import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.WeakHashMap;

import net.sourceforge.phpeclipse.css.core.CssCore;
import net.sourceforge.phpeclipse.css.core.internal.CssCorePreferences;
import net.sourceforge.phpeclipse.css.core.profiles.IProfile;
import net.sourceforge.phpeclipse.css.core.profiles.IProfileDescriptor;
import net.sourceforge.phpeclipse.css.core.profiles.IProfileManager;

import org.eclipse.core.resources.IProject;
import org.eclipse.core.resources.IResource;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtension;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.Preferences;
import org.eclipse.core.runtime.QualifiedName;

/**
 * Implementation of the <code>IProfileManager</code> interface.
 */
public class ProfileManager implements IProfileManager {

	// Constants ---------------------------------------------------------------

	/**
	 * The qualified name used to persist the selected profile on projects and
	 * resources.
	 */
	public static final QualifiedName PROFILE_PROPERTY =
		new QualifiedName(CssCore.getPluginId(), "profile"); //$NON-NLS-1$

	// Instance Variables ------------------------------------------------------

	/**
	 * The plugin preferences.
	 */
	private Preferences preferences;

	/**
	 * The profile descriptors, keyed by extension ID.
	 */
	private Map profileDescriptors;

	/**
	 * Cache of the already loaded profiles.
	 */
	private Map profiles = new WeakHashMap();

	// Constructors ------------------------------------------------------------

	/**
	 * Constructor.
	 * 
	 * @param preferences the plugin preferences
	 */
	public ProfileManager(Preferences preferences) {
		this.preferences = preferences;
	}

	// IProfileManager Implementation ------------------------------------------

	/**
	 * @see IProfileManager#getProfileDescriptors()
	 */
	public IProfileDescriptor[] getProfileDescriptors() {
		if (profileDescriptors == null) {
			loadProfileExtensions();
		}
		List retVal = new ArrayList();
		retVal.addAll(profileDescriptors.values());
		return (IProfileDescriptor[]) retVal.toArray(
			new IProfileDescriptor[retVal.size()]);
	}

	/**
	 * @see IProfileManager#getProfile(IResource)
	 */
	public IProfile getProfile(IResource resource) {
		String profileId = null;
		if (resource != null) {
			try {
				profileId = resource.getPersistentProperty(PROFILE_PROPERTY);
			} catch (CoreException e) {
				CssCore.log(
					"Failed to get profile for resource", e); //$NON-NLS-1$
			}
			if (profileId == null) {
				IProject project = resource.getProject();
				try {
					profileId = project.getPersistentProperty(PROFILE_PROPERTY);
				} catch (CoreException e) {
					CssCore.log(
						"Failed to get profile for project", e); //$NON-NLS-1$
				}
			}
		}
		if (profileId == null) {
			profileId = preferences.getString(CssCorePreferences.PROFILE);
		}
		IProfile profile = getProfile(profileId);
		return profile;
	}

	/**
	 * @see IProfileManager#setProfile(IResource, String)
	 */
	public void setProfile(IResource resource, String profileId) {
		if (resource != null) {
			try {
				resource.setPersistentProperty(
					ProfileManager.PROFILE_PROPERTY, profileId);
			} catch (CoreException e) {
				CssCore.log(
					"Cannot store profile as resource property", //$NON-NLS-1$
					e);
			}
		} else if (profileId != null) {
			preferences.setValue(CssCorePreferences.PROFILE, profileId);
		} else {
			preferences.setToDefault(CssCorePreferences.PROFILE);
		}
	}

	// Private Methods ---------------------------------------------------------

	/**
	 * Returns the profile associated with the specified extension ID. The
	 * profile is instantiated if not already in the cache.
	 * 
	 * @param profileId the ID of the extension implementing the profile
	 */
	private IProfile getProfile(String profileId) {
		IProfile profile = (IProfile) profiles.get(profileId);
		if (profile == null) {
			IProfileDescriptor descriptor = getProfileDescriptor(profileId);
			if (descriptor == null) {
				CssCore.log("Profile '" + profileId + //$NON-NLS-1$
					"' not found."); //$NON-NLS-1$
				descriptor = getDefaultProfileDescriptor();
			}
			if (descriptor != null) {
				profile = instantiateProfile(descriptor);
				profiles.put(profileId, profile);
			}
		}
		return profile;
	}

	/**
	 * Returns the descriptor of the default profile.
	 * 
	 * @return the descriptor of the default profile
	 */
	private IProfileDescriptor getDefaultProfileDescriptor() {
		String profileId = preferences.getDefaultString(
				CssCorePreferences.PROFILE);
		return getProfileDescriptor(profileId);
	}

	/**
	 * Returns the descriptor of the specified profile.
	 * 
	 * @param profileId the ID of the profile
	 * @return the descriptor of the profile with the given ID
	 */
	private IProfileDescriptor getProfileDescriptor(String profileId) {
		if (profileDescriptors == null) {
			loadProfileExtensions();
		}
		return (IProfileDescriptor) profileDescriptors.get(profileId);
	}

	/**
	 * Instantiates and the returns the profile.
	 * 
	 * @param descriptor the profile descriptor
	 * @return the instantiated profile, or <code>null</code> if there was a 
	 *         problem instantiating the profile
	 */
	private IProfile instantiateProfile(IProfileDescriptor descriptor) {
		try {
			Class clazz = Class.forName(descriptor.getClassName());
			Constructor ctor = clazz.getConstructor(
				new Class[] { IProfileDescriptor.class });
			return (IProfile) ctor.newInstance(new Object[] { descriptor });
		} catch (Exception e) {
			CssCore.log("Failed to get CSS profile", e); //$NON-NLS-1$
		}
		return null;
	}

	/**
	 * Initializes the list of available profiles by querying the platform for
	 * extensions of the <em>profiles</em> extension point and storing an
	 * <code>IProfileDescriptor</code> for each extension found.
	 */
	private void loadProfileExtensions() {
		profileDescriptors = new HashMap();
		IExtensionRegistry registry = Platform.getExtensionRegistry();
		IExtensionPoint extensionPoint = registry.getExtensionPoint(
			IProfileDescriptor.EXTENSION_POINT_ID);
		IExtension[] extensions = extensionPoint.getExtensions();
		for (int i = 0; i < extensions.length; i++) {
			IExtension extension = extensions[i];
			IConfigurationElement[] elements =
				extension.getConfigurationElements();
			for (int j = 0; j < elements.length; j++) {
				IConfigurationElement element = elements[j];
				IProfileDescriptor descriptor = new ProfileDescriptor(element);
				profileDescriptors.put(descriptor.getId(), descriptor);
			}
		}
	}
}