/*
    * Copyright (C) 2007-2012 Argeo GmbH
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *         http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.argeo.eclipse.ui.specific;
  
  import static org.argeo.eclipse.ui.util.SingleSourcingConstants.FILE_SCHEME;
  import static org.argeo.eclipse.ui.util.SingleSourcingConstants.SCHEME_HOST_SEPARATOR;
  
  import java.io.IOException;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.argeo.eclipse.ui.EclipseUiUtils;
  import org.argeo.eclipse.ui.util.SingleSourcingConstants;
  import org.eclipse.rap.rwt.service.ServiceHandler;
  
  /**
   * RWT specific Basic Default service handler that retrieves a file on the
   * server file system using its absolute path and forwards it to the end user
   * browser.
   * 
   * Clients might extend to provide context specific services
   */
  public class OpenFileService implements ServiceHandler {
  	public OpenFileService() {
  	}
  
  	public void service(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
  		String fileName = request.getParameter(SingleSourcingConstants.PARAM_FILE_NAME);
  		String uri = request.getParameter(SingleSourcingConstants.PARAM_FILE_URI);
  
  		// Use buffered array to directly write the stream?
  		if (!uri.startsWith(SingleSourcingConstants.FILE_SCHEME))
  			throw new IllegalArgumentException(
  					"Open file service can only handle files that are on the server file system");
  
  		// Set the Metadata
  		response.setContentLength((int) getFileSize(uri));
  		if (EclipseUiUtils.isEmpty(fileName))
  			fileName = getFileName(uri);
  		response.setContentType(getMimeType(uri, fileName));
  		String contentDisposition = "attachment; filename=\"" + fileName + "\"";
  		response.setHeader("Content-Disposition", contentDisposition);
  
  		// Useless for current use
  		// response.setHeader("Content-Transfer-Encoding", "binary");
  		// response.setHeader("Pragma", "no-cache");
  		// response.setHeader("Cache-Control", "no-cache, must-revalidate");
  
  		Path path = Paths.get(getAbsPathFromUri(uri));
  		Files.copy(path, response.getOutputStream());
  
  		// FIXME we always use temporary files for the time being.
  		// the deleteOnClose file only works when the JVM is closed so we
  		// explicitly delete to avoid overloading the server
  		if (path.startsWith("/tmp"))
  			path.toFile().delete();
  	}
  
  	protected long getFileSize(String uri) throws IOException {
  		if (uri.startsWith(SingleSourcingConstants.FILE_SCHEME)) {
  			Path path = Paths.get(getAbsPathFromUri(uri));
  			return Files.size(path);
  		}
  		return -1l;
  	}
  
  	protected String getFileName(String uri) {
  		if (uri.startsWith(SingleSourcingConstants.FILE_SCHEME)) {
  			Path path = Paths.get(getAbsPathFromUri(uri));
  			return path.getFileName().toString();
  		}
  		return null;
  	}
  
  	private String getAbsPathFromUri(String uri) {
  		if (uri.startsWith(FILE_SCHEME))
  			return uri.substring((FILE_SCHEME + SCHEME_HOST_SEPARATOR).length());
  		// else if (uri.startsWith(JCR_SCHEME))
  		// return uri.substring((JCR_SCHEME + SCHEME_HOST_SEPARATOR).length());
  		else
  			throw new IllegalArgumentException("Unknown URI prefix for" + uri);
 	}
 
 	protected String getMimeType(String uri, String fileName) throws IOException {
 		if (uri.startsWith(FILE_SCHEME)) {
 			Path path = Paths.get(getAbsPathFromUri(uri));
 			String mimeType = Files.probeContentType(path);
 			if (EclipseUiUtils.notEmpty(mimeType))
 				return mimeType;
 		}
 		return "application/octet-stream";
 	}
 }