/**
 ********************************************************************************
 * Copyright (c) 2021-2022 Robert Bosch GmbH and others.
 *
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     Robert Bosch GmbH - initial API and implementation
 ********************************************************************************
 */

package org.eclipse.app4mc.amalthea.model.editor.handler;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

import javax.inject.Named;

import org.eclipse.app4mc.amalthea.model.editor.container.AmaltheaModelContainer;
import org.eclipse.app4mc.amalthea.model.editor.util.AmaltheaEditorUtil;
import org.eclipse.app4mc.amalthea.model.emf.AmaltheaResource;
import org.eclipse.app4mc.amalthea.model.io.AmaltheaFileHelper;
import org.eclipse.core.resources.IFile;
import org.eclipse.core.resources.IResource;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.Platform;
import org.eclipse.e4.core.di.annotations.Execute;
import org.eclipse.e4.ui.services.IServiceConstants;
import org.eclipse.emf.ecore.resource.Resource;
import org.eclipse.emf.ecore.resource.ResourceSet;
import org.eclipse.jface.dialogs.MessageDialog;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.ui.IDecoratorManager;
import org.eclipse.ui.PlatformUI;

public class UncompressHandler {

	private static final int BUFFER_SIZE = 2048;
	private static final long MAX_FILE_SIZE = 2_000_000_000L; // 2 GB
	private static final String COMPRESS_ERROR = "Compress error";

	@Execute
	public void execute(@Named(IServiceConstants.ACTIVE_SELECTION) IStructuredSelection selection, Shell shell, IDecoratorManager decoratorManager) {
		Object firstElement = selection.getFirstElement();
		if (firstElement instanceof IFile) {
			IFile iFile = (IFile) firstElement;
			
			if (AmaltheaFileHelper.isModelFileExtension(iFile.getFileExtension())) {
				AmaltheaModelContainer modelContainer = AmaltheaEditorUtil.getModelContainer(iFile);
				
				if (modelContainer != null && modelContainer.getInitialModelFiles().contains(iFile)) {
					// Resource is available (model is in memory)
					markResourceUnzipped(iFile, modelContainer);
					// Give feedback to user (because file will not be changed immediately)
					showInfoDialog();
				} else {
					// Unzip model file
					unzipModelFile(iFile, shell, decoratorManager);
				}
			}
		}
	}

	private void showInfoDialog() {
		Display.getDefault().asyncExec( () -> MessageDialog.openInformation(
				PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell(),
				"Uncompress",
				"Resource successfully marked as \"expanded\".\n\nSave the model to persist changes.") );
	}

	private void markResourceUnzipped(IFile iFile, AmaltheaModelContainer modelContainer) {
		ResourceSet resourceSet = modelContainer.getResourceSet();
		if (resourceSet != null) {
			for (Resource resource : resourceSet.getResources()) {
				if (resource instanceof AmaltheaResource && resource.getURI().lastSegment().equals(iFile.getName())) {
					// Modify zip flag of loaded resource
					((AmaltheaResource) resource).setUseZip(false);
					// Mark resource as modified
					resource.setModified(true);
					// Mark editors dirty
					modelContainer.updateDirtyStateOfEditors();
					break;
				}
			}
		}
	}

	/**
	 * Extracts first file of Zip archive (generic implementation based on java.util.zip package)
	 *
	 * Following vulnerabilities are handled:
	 * - Zip Slip (https://snyk.io/research/zip-slip-vulnerability)
	 * - Zip Bomb (https://wiki.sei.cmu.edu/confluence/display/java/IDS04-J.+Safely+extract+files+from+ZipInputStream)
	 *
	 * @param iFile
	 * @param shell
	 * @param decoratorManager
	 */
	private void unzipModelFile(IFile iFile, Shell shell, IDecoratorManager decoratorManager) {
		if (!AmaltheaEditorUtil.isZipFile(iFile)) {
			MessageDialog.openError(shell, COMPRESS_ERROR, "Invalid file!");
			return; // stop further actions
		}

		File modelFile = AmaltheaEditorUtil.getLocalFile(iFile);
		File modelFileTmp = new File(modelFile.getParentFile(), modelFile.getName() + ".tmp");

		// Unzip model file (write first entry to temporary file)
		try (	ZipInputStream inputStream = new ZipInputStream(new FileInputStream(modelFile));
				FileOutputStream outputStream = new FileOutputStream(modelFileTmp);)
		{
			ZipEntry zipEntry = inputStream.getNextEntry();
			if (zipEntry != null && !zipEntry.isDirectory()) {
				long total = 0;
				byte[] bytes = new byte[BUFFER_SIZE];
				int length;
				while((length = inputStream.read(bytes)) > 0) {
					// check size of extracted data (to avoid Zip bombs)
					if (total + length > MAX_FILE_SIZE) {
						MessageDialog.openError(shell, COMPRESS_ERROR, "File being unzipped is too big.");
						return; // stop further actions
					}

					outputStream.write(bytes, 0, length);
					total += length;
				}
			}
		} catch (IOException e) {
			MessageDialog.openError(shell, COMPRESS_ERROR, "Failed to uncompress model file! " + e.getMessage());
			return; // stop further actions
		}

		// Delete old model file and rename temporary file
		try {
			Files.delete(modelFile.toPath());
			Files.move(modelFileTmp.toPath(), modelFile.toPath());
		} catch (IOException e) {
			MessageDialog.openError(shell, COMPRESS_ERROR, "Failed to replace model file! " + e.getMessage());
		}

		// Refresh file and decorators
		try {
			iFile.refreshLocal(IResource.DEPTH_INFINITE, null);
			decoratorManager.update("org.eclipse.app4mc.amalthea.file.compressed.decorator");
		} catch (CoreException e) {
			Platform.getLog(getClass()).error(e.getLocalizedMessage(), e);
		}
	}

}