/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * 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:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.message.internal;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtension;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.dynamichelpers.ExtensionTracker;
import org.eclipse.core.runtime.dynamichelpers.IExtensionChangeHandler;
import org.eclipse.core.runtime.dynamichelpers.IExtensionTracker;
import org.eclipse.core.runtime.dynamichelpers.IFilter;
import org.simantics.message.IMessageDataSchemeExtension;
import org.simantics.message.IMessageSchemeManager;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author Tuukka Lehtonen
 */
public class MessageSchemeManager implements IExtensionChangeHandler, IMessageSchemeManager {

    private static final Logger LOGGER = LoggerFactory.getLogger(MessageSchemeManager.class);
    public final static String           NAMESPACE    = "org.simantics.message";
    public final static String           ELEMENT_NAME = "scheme";
    public final static String           EP_NAME      = "messageDataScheme";

    private ExtensionTracker             tracker;

    private MessageDataSchemeExtension[] extensions   = new MessageDataSchemeExtension[0];

    public MessageSchemeManager() {
        tracker = new ExtensionTracker();

        // Cache defined actions
        IExtensionPoint expt = Platform.getExtensionRegistry().getExtensionPoint(NAMESPACE, EP_NAME);
        loadExtensions(expt.getConfigurationElements());

        // Start tracking for new and removed extensions
        IFilter filter = ExtensionTracker.createExtensionPointFilter(expt);
        tracker.registerHandler(this, filter);
    }

    private String getDescription(IConfigurationElement el) {
        for (IConfigurationElement desc : el.getChildren("description")) {
            return desc.getValue();
        }
        return null;
    }
    
    private void loadExtensions(IConfigurationElement[] configurationElements) {
        Set<MessageDataSchemeExtension> newExtensions = new HashSet<MessageDataSchemeExtension>(Arrays.asList(extensions));
        
        // Initialize id -> extension lookup
        Map<String, MessageDataSchemeExtension> schemes = new HashMap<String, MessageDataSchemeExtension>();
        for (MessageDataSchemeExtension ext : newExtensions) {
            schemes.put(ext.getId(), ext);
        }

        // 1st pass: load schemes
        for (IConfigurationElement el : configurationElements) {
            String name = el.getName();
            if ("scheme".equals(name)) {
                String id = el.getAttribute("id");
                if (id == null)
                    continue;
                String scheme = el.getAttribute("scheme");
                if (scheme == null)
                    continue;
                String description = getDescription(el);
                
                MessageDataSchemeExtension ext = schemes.get(id);
                if (ext != null) {
                    // This scheme is already registered, two contributors are contributing the same scheme.
                    StringBuilder msg = new StringBuilder();
                    msg.append("Multiple contributors for message scheme '" + id + "':");
                    msg.append("\n  1st: " + ext.getSchemeElement().getContributor().getName());
                    msg.append("\n  2nd: " + el.getContributor().getName());
                    msg.append("\nUsing the first one.");
                    LOGGER.info(msg.toString());
                    continue;
                }

                ext = new MessageDataSchemeExtension(el, id, scheme, description);

                // Start tracking the new extension object, its removal will be notified of
                // with removeExtension(extension, Object[]).
                tracker.registerObject(el.getDeclaringExtension(), ext, IExtensionTracker.REF_STRONG);

                newExtensions.add(ext);
                schemes.put(id, ext);
            }
        }

        // 2nd pass: load handlers
        for (IConfigurationElement el : configurationElements) {
            String name = el.getName();
            if ("handler".equals(name)) {
                String id = el.getAttribute("schemeId");
                if (id == null)
                    continue;

                MessageDataSchemeExtension ext = schemes.get(id);
                if (ext == null) {
                    // Unusable handler since there is no scheme to use it for.
                    StringBuilder msg = new StringBuilder();
                    msg.append("No scheme extension for message scheme id '" + id + "'. Ignoring handler '" + el.getAttribute("handler") + "'");
                    msg.append("\nUsing the first one.");
                    LOGGER.info(msg.toString());
                    continue;
                }

                IConfigurationElement prev = ext.getHandlerElement();
                if (prev != null) {
                    // Unusable handler since there already exists a handler for this scheme.
                    StringBuilder msg = new StringBuilder();
                    msg.append("Multiple handler contributors for message scheme '" + id + "':\n");
                    msg.append("\n   1st: " + prev.getContributor().getName());
                    msg.append("\n   2nd: " + el.getContributor().getName());
                    msg.append("\nUsing the first one.");
                    LOGGER.info(msg.toString());
                    continue;
                }

                ext.setHandlerElement(el);
            }
        }

        // Atomic assignment
        this.extensions = newExtensions.toArray(new MessageDataSchemeExtension[newExtensions.size()]);
    }

    @Override
    public void addExtension(IExtensionTracker tracker, IExtension extension) {
        loadExtensions(extension.getConfigurationElements());
    }

    @Override
    public void removeExtension(IExtension extension, Object[] objects) {
        Set<MessageDataSchemeExtension> newExtensions = new HashSet<MessageDataSchemeExtension>(Arrays.asList(extensions));

        for (Object o : objects) {
            tracker.unregisterObject(extension, o);
            newExtensions.remove((IMessageDataSchemeExtension) o);
        }

        // Atomic assignment
        this.extensions = newExtensions.toArray(new MessageDataSchemeExtension[newExtensions.size()]);
    }

    @Override
    public IMessageDataSchemeExtension[] getByScheme(String scheme) {
        if (scheme == null)
            throw new IllegalArgumentException("null scheme");

        ArrayList<MessageDataSchemeExtension> result = new ArrayList<MessageDataSchemeExtension>();
        for (MessageDataSchemeExtension ext : extensions) {
            if (scheme.equals(ext.getScheme()))
                result.add(ext);
        }
        return result.toArray(new MessageDataSchemeExtension[result.size()]);
    }

}