/*
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.xwiki.rendering.internal.macro.wikibridge;

import java.util.Arrays;
import java.util.List;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;

import org.slf4j.Logger;
import org.xwiki.bridge.DocumentModelBridge;
import org.xwiki.bridge.event.AbstractDocumentEvent;
import org.xwiki.bridge.event.DocumentCreatedEvent;
import org.xwiki.bridge.event.DocumentDeletedEvent;
import org.xwiki.bridge.event.DocumentUpdatedEvent;
import org.xwiki.component.annotation.Component;
import org.xwiki.model.reference.DocumentReference;
import org.xwiki.observation.EventListener;
import org.xwiki.observation.event.Event;
import org.xwiki.rendering.macro.wikibridge.InsufficientPrivilegesException;
import org.xwiki.rendering.macro.wikibridge.WikiMacro;
import org.xwiki.rendering.macro.wikibridge.WikiMacroException;
import org.xwiki.rendering.macro.wikibridge.WikiMacroFactory;
import org.xwiki.rendering.macro.wikibridge.WikiMacroManager;

/**
 * An {@link EventListener} responsible for dynamically registering / unregistering / updating xwiki rendering macros
 * based on wiki macro create / delete / update actions.
 * 
 * @version $Id: bf389787c3333b4ef62a5cd2b7dd283197d4f05f $
 * @since 2.0M2
 */
@Component
@Named("wikimacrolistener")
@Singleton
public class WikiMacroEventListener implements EventListener
{
    /**
     * The {@link org.xwiki.rendering.macro.wikibridge.WikiMacroFactory} component.
     */
    @Inject
    private WikiMacroFactory macroFactory;

    /**
     * The {@link WikiMacroManager} component.
     */
    @Inject
    private WikiMacroManager wikiMacroManager;

    /**
     * The logger to log.
     */
    @Inject
    private Logger logger;

    @Override
    public String getName()
    {
        return "wikimacrolistener";
    }

    @Override
    public List<Event> getEvents()
    {
        return Arrays
            .<Event> asList(new DocumentCreatedEvent(), new DocumentUpdatedEvent(), new DocumentDeletedEvent());
    }

    @Override
    public void onEvent(Event event, Object source, Object data)
    {
        if (event instanceof AbstractDocumentEvent) {
            DocumentModelBridge document = (DocumentModelBridge) source;
            DocumentReference documentReference = document.getDocumentReference();

            // We've decided not to log any exception raised in the XWiki logs since a failure to register or
            // unregister a macro isn't a failure of the XWiki software. It's something normal, same as, for example,
            // not being able to edit a page if the user doesn't have edit rights.
            // The problem here is that since Macros are registered by an Event Listener there's no way defined
            // to let the user know about the status. We'd need to:
            // - create a status page listing the state of all macros with the last error messages
            // - don't use a listener to register macros and instead have a page listing all macros with a
            // register/unregister button (and thus provide visual feedback when the action fails).

            if (event instanceof DocumentCreatedEvent || event instanceof DocumentUpdatedEvent) {
                registerMacro(documentReference);
            } else if (event instanceof DocumentDeletedEvent) {
                unregisterMacro(documentReference);
            }
        }
    }

    /**
     * @param documentReference the reference of the document containing the macro to register
     */
    private void registerMacro(DocumentReference documentReference)
    {
        // Unregister any existing macro registered under this document.
        if (unregisterMacro(documentReference)) {
            // Check whether the given document has a wiki macro defined in it.
            if (this.macroFactory.containsWikiMacro(documentReference)) {
                // Attempt to create a wiki macro.
                WikiMacro wikiMacro;
                try {
                    wikiMacro = this.macroFactory.createWikiMacro(documentReference);
                } catch (WikiMacroException e) {
                    this.logger.debug(String.format("Failed to create wiki macro [%s]", documentReference), e);
                    return;
                }

                // Register the macro.
                registerMacro(documentReference, wikiMacro);
            }
        }
    }

    /**
     * Register a new wiki macro.
     * 
     * @param documentReference the reference of the document containing the wiki macro to register
     * @param wikiMacro the wiki macro to register
     */
    private void registerMacro(DocumentReference documentReference, WikiMacro wikiMacro)
    {
        try {
            this.wikiMacroManager.registerWikiMacro(documentReference, wikiMacro);
        } catch (WikiMacroException e) {
            this.logger.debug(
                String.format("Unable to register macro [%s] in document [%s]", wikiMacro.getDescriptor().getId()
                    .getId(), documentReference), e);
        } catch (InsufficientPrivilegesException e) {
            this.logger.debug(String.format("Insufficient privileges for registering macro [%s] in document [%s]",
                wikiMacro.getDescriptor().getId().getId(), documentReference), e);
        }
    }

    /**
     * Unregister wiki macro.
     * 
     * @param documentReference the reference of the document containing the wiki macro to register
     * @return false if failed to unregister wiki macro, true otherwise
     */
    private boolean unregisterMacro(DocumentReference documentReference)
    {
        boolean result = true;
        if (this.wikiMacroManager.hasWikiMacro(documentReference)) {
            try {
                this.wikiMacroManager.unregisterWikiMacro(documentReference);
            } catch (WikiMacroException e) {
                this.logger.debug(String.format("Unable to unregister macro in document [%s]", documentReference), e);
                result = false;
            }
        }

        return result;
    }
}