/*******************************************************************************
 * Copyright (c) 2005 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package model;

import java.io.File;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Calendar;
import java.util.Collections;

import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.ecore.resource.Resource;
import org.eclipse.emf.ecore.resource.ResourceSet;
import org.eclipse.emf.ecore.resource.impl.ResourceSetImpl;
import org.eclipse.ui.examples.rcp.adventure.AdventurePackage;
import org.eclipse.ui.examples.rcp.adventure.Catalog;
import org.eclipse.ui.examples.rcp.adventure.GlobalSettings;

/**
 * A caching adapter implementation of the catalog service.
 * This saves a cache of the catalog obtained from the catalog web service
 * as an XMI file in the plug-ins metadata area of the workspace.
 */
public class CachingCatalogService implements ICatalogService {
	private static final String FILE_NAME = "catalog.xmi";

	private WebCatalogService webCatalogService;

	public CachingCatalogService(WebCatalogService webCatService) {
		this.webCatalogService = webCatService;
	}

	public Catalog getCatalog() {
		return (Catalog) AccessController.doPrivileged(new PrivilegedAction() {
			public Object run() {
				return getCatalog0();
			}
		});
	}
	private Catalog getCatalog0() {
//		for (int i = 0; i < 20; ++i) {
//			long t = System.currentTimeMillis();
//			long lm = webCatalogService.getLastModified().getTimeInMillis();
//			t = System.currentTimeMillis() - t;
//			System.out.println("t=" + t + "  lm=" + lm);
//		}
		GlobalSettings settings = AdventureBuilderModel.getDefault().getGlobalSettings();
		if (settings.isCacheCatalog()) {
			Catalog cachedCatalog = readCachedCatalog();
			if (cachedCatalog != null) {
				if (settings.isDisconnectedMode()) {
					cachedCatalog.setSource("Cache (disconnected)");
					return cachedCatalog;
				}
				Calendar webLastModified = webCatalogService.getLastModified();
				if (webLastModified == null) {
					cachedCatalog.setSource("Cache (web service unreachable)");
					return cachedCatalog;
				}
				if (cachedCatalog.getLastModified() == webLastModified.getTimeInMillis()) {
					cachedCatalog.setSource("Cache (same timestamp as Web Service)");
					return cachedCatalog;
				}
			}
		}
		if (!settings.isDisconnectedMode()) {
			Catalog catalog = webCatalogService.getCatalog();
			if (catalog != null) {
				if (settings.isCacheCatalog()) {
					cacheCatalog(catalog);
				}
				return catalog;
			}
		}
		return new DummyCatalogService().getCatalog();
	}

	public void clearCache() {
		File cacheFile = new File(getCacheFileName());
		if (cacheFile.exists()) {
			System.out.println("Clearing cached catalog.");
			cacheFile.delete();
			if (cacheFile.exists()) {
				System.out.println("Error clearing cache.  Cache file still exists.");
			}
			else {
				System.out.println("Cache cleared successfully.");
			}
		}
		else {
			System.out.println("No cached catalog to clear.");
		}

	}

	private Catalog readCachedCatalog() {
		long t = System.currentTimeMillis();
		String cacheFileName = getCacheFileName();
		if (!new File(cacheFileName).exists()) {
			return null;
		}
		// Create a resource set.
		ResourceSet resourceSet = new ResourceSetImpl();

		// Register the default resource factory -- only needed for stand-alone!
		// resourceSet.getResourceFactoryRegistry().getExtensionToFactoryMap().put(
		// Resource.Factory.Registry.DEFAULT_EXTENSION, new
		// XMIResourceFactoryImpl());

		// Register the package -- only needed for stand-alone!
		AdventurePackage adventurePackage = AdventurePackage.eINSTANCE;

		// Get the URI of the model file.
		URI fileURI = URI.createFileURI(getCacheFileName());

		try {
			// Demand load the resource for this file.
			Resource resource = resourceSet.getResource(fileURI, true);
			if (resource == null) {
				// TODO: Improve error handling
				System.out.println("Unable to get resource for cache file.  Is org.eclipse.emf.ecore.xmi installed?");
				return null;
			}
			if (resource.getContents().isEmpty()) {
				// TODO: Improve error handling
				System.out.println("Invalid cache file: no resources");
				return null;
			}
			Object first = resource.getContents().get(0);
			if (!(first instanceof Catalog)) {
				// TODO: Improve error handling
				System.out.println("Invalid cache file: first resource is not a Catalog");
				return null;
			}
			Catalog catalog = (Catalog) first;
			t = System.currentTimeMillis() - t;
			catalog.setTimeToRead(t);
			catalog.setSource("Cache");
			return catalog;
		} catch (Exception e) {
			// TODO: Improve error handling
			System.out.println(e);
			return null;
		}

	}

	private void cacheCatalog(Catalog catalog) {
		// Create a resource set.
		ResourceSet resourceSet = new ResourceSetImpl();

		// Register the default resource factory -- only needed for stand-alone!
		// resourceSet.getResourceFactoryRegistry().getExtensionToFactoryMap().put(
		// Resource.Factory.Registry.DEFAULT_EXTENSION, new
		// XMIResourceFactoryImpl());

		// Get the URI of the model file.
		URI fileURI = URI.createFileURI(getCacheFileName());

		// Create a resource for this file.
		Resource resource = resourceSet.createResource(fileURI);

		if (resource == null) {
			// TODO: Improve error handling
			System.out.println("Unable to create resource for cache file.  Is org.eclipse.emf.ecore.xmi installed?");
			return;
		}

		// Add the catalog to the contents.
		resource.getContents().add(catalog);

		// Save the contents of the resource to the file system.
		try {
			resource.save(Collections.EMPTY_MAP);
		} catch (IOException e) {
			// TODO: Improve error handling
			System.out.println(e);
		}
	}

	private String getCacheFileName() {
		return AdventureBuilderModel.getDefault().getStateLocation().append(
				FILE_NAME).toOSString();
	}
}