/*******************************************************************************
 * Copyright (c) 2013 SAP AG.
 * 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:
 *    Eduard Bartsch (SAP AG) - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.resources.semantic;

import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.eclipse.core.internal.resources.semantic.model.SemanticResourceDB.ResourceTreeNode;
import org.eclipse.core.internal.resources.semantic.model.SemanticResourceDB.SemanticDB;
import org.eclipse.core.internal.resources.semantic.model.SemanticResourceDB.SemanticResourceDBFactory;
import org.eclipse.core.internal.resources.semantic.model.SemanticResourceDB.SemanticResourceDBPackage;
import org.eclipse.core.internal.resources.semantic.model.SemanticResourceDB.TreeRoot;
import org.eclipse.core.runtime.IPath;
import org.eclipse.core.runtime.Path;
import org.eclipse.emf.common.util.EList;
import org.eclipse.emf.common.util.TreeIterator;
import org.eclipse.emf.ecore.EObject;
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.emf.ecore.xmi.impl.XMIResourceFactoryImpl;

public class SemanticMetadataPersistenceManager {

	private static final String METADATA_FILENAME = "metadata.xmi"; //$NON-NLS-1$
	final static IPath EMPTY = new Path(""); //$NON-NLS-1$

	private SemanticDB db;

	private Map<String, Resource> metadataResourceMap = new HashMap<String, Resource>();
	private File metadataFolder;
	Resource metadataResource;
	ResourceSet metadataResourceSet = new ResourceSetImpl();

	public SemanticMetadataPersistenceManager(File metadataFolder) {
		this.metadataFolder = metadataFolder;
	}

	public SemanticDB getSemanticDB() {
		return db;
	}

	public String getMetadataResourceLocation(String name) {
		return getMetadataFile(name).getAbsolutePath();
	}

	public String getMetadataFileName(String name) {
		return "$." + name + ".xmi"; //$NON-NLS-1$ //$NON-NLS-2$
	}

	public void init() throws IOException {
		// Register the appropriate resource factory to handle all file
		// extensions that would cover XMI as well.
		metadataResourceSet.getResourceFactoryRegistry().getExtensionToFactoryMap()
				.put(Resource.Factory.Registry.DEFAULT_EXTENSION, new XMIResourceFactoryImpl());

		metadataFolder.mkdirs();

		File metadataFile = getMetadataFile(null);

		if (!metadataFile.exists()) {
			initSemanticDB();
		} else {
			loadSemanticDB();
		}
	}

	public void initSemanticDB() {
		this.metadataResource = metadataResourceSet.createResource(getResourceURI(METADATA_FILENAME));

		this.db = SemanticResourceDBFactory.eINSTANCE.createSemanticDB();

		this.metadataResource.getContents().add(this.db);
	}

	private void loadSemanticDB() throws IOException {
		SemanticResourceDBPackage pkg = SemanticResourceDBPackage.eINSTANCE;
		pkg.eClass();

		this.metadataResource = metadataResourceSet.createResource(getResourceURI(METADATA_FILENAME));

		this.metadataResource.load(null);

		EList<EObject> contents = this.metadataResource.getContents();

		for (EObject eObject : contents) {
			if (eObject instanceof SemanticDB) {
				this.db = (SemanticDB) eObject;
				this.migrateSemanticDB();
				break;
			}
		}
	}

	public void saveSemanticDB(String projectName) throws IOException {
		if (SfsTraceLocation.CORE_DB.isActive()) {
			SfsTraceLocation.getTrace().traceEntry(SfsTraceLocation.CORE_DB.getLocation());
		}

		// force assignment to separate resources
		EList<TreeRoot> roots = this.db.getRoots();
		for (TreeRoot treeRoot : roots) {
			if (projectName == null || projectName.equals(treeRoot.getName())) {
				assignToProjectSpecificMetadataResource(treeRoot);
			}
		}

		this.metadataResource.save(null);

		if (projectName == null) {
			for (Entry<String, Resource> resourceEntry : this.metadataResourceMap.entrySet()) {
				resourceEntry.getValue().save(null);
			}
		} else {
			Resource resource = this.metadataResourceMap.get(projectName);

			resource.save(null);
		}
	}

	public File getMetadataFile(String name) {
		String fileName;

		if (name != null) {
			fileName = getMetadataFileName(name);
		} else {
			fileName = METADATA_FILENAME;
		}

		return new File(metadataFolder, fileName);
	}

	public void migrateSemanticDB() throws IOException {
		TreeIterator<EObject> objects = this.db.eAllContents();
		ArrayList<ResourceTreeNode> toBeRemoved = new ArrayList<ResourceTreeNode>();
		Set<String> filesToBeRemoved = listMetadataFiles();

		while (objects.hasNext()) {
			EObject eObject = objects.next();
			if (eObject instanceof TreeRoot) {
				TreeRoot root = (TreeRoot) eObject;

				if (!root.isExists()) {
					toBeRemoved.add(root);
				} else {
					assignToProjectSpecificMetadataResource(root);
					filesToBeRemoved.remove(getMetadataFileName(root.getName()));
				}
			} else if (eObject instanceof ResourceTreeNode) {
				ResourceTreeNode node = (ResourceTreeNode) eObject;

				if (!node.isExists()) {
					toBeRemoved.add(node);
				}
			}
		}

		for (ResourceTreeNode resourceTreeNode : toBeRemoved) {
			if (resourceTreeNode instanceof TreeRoot) {
				((TreeRoot) resourceTreeNode).setParentDB(null);
				this.db.getRoots().remove(resourceTreeNode);
			} else {
				resourceTreeNode.setParent(null);
			}
		}

		for (String fileName : filesToBeRemoved) {
			File file = new File(this.metadataFolder, fileName);
			if (file.exists()) {
				file.delete();
			}
		}

		this.metadataResource.save(null);

		for (String name : this.metadataResourceMap.keySet()) {
			File file = getMetadataFile(name);

			if (!file.exists()) {
				Resource resource = this.metadataResourceMap.get(name);

				resource.save(null);
			}
		}
	}

	private Set<String> listMetadataFiles() {
		File[] files = this.metadataFolder.listFiles(new FilenameFilter() {
			public boolean accept(File dir, String name) {
				return name.endsWith(".xmi") && !name.equals(METADATA_FILENAME); //$NON-NLS-1$
			}
		});

		Set<String> names = new HashSet<String>();
		for (File file : files) {
			names.add(file.getName());
		}
		return names;
	}

	private void assignToProjectSpecificMetadataResource(TreeRoot root) {
		Resource resource = this.metadataResourceMap.get(root.getName());

		if (resource == null) {
			org.eclipse.emf.common.util.URI uri = org.eclipse.emf.common.util.URI
					.createFileURI(getMetadataResourceLocation(root.getName()));
			resource = this.metadataResourceSet.createResource(uri);
			this.metadataResourceMap.put(root.getName(), resource);
		}

		resource.getContents().add(root);
	}

	private org.eclipse.emf.common.util.URI getResourceURI(String fileName) {
		File metadataFile = new File(metadataFolder, fileName);

		String metadataLocation = metadataFile.getAbsolutePath();

		return org.eclipse.emf.common.util.URI.createFileURI(metadataLocation);
	}

	public Resource getMetadataResource() {
		return this.metadataResource;
	}

}