/*
    * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  package org.eclipse.jgit.lfs.server.fs;
  
  import java.io.IOException;
  import java.io.PrintWriter;
  import java.text.MessageFormat;
  
  import javax.servlet.AsyncContext;
  import javax.servlet.ServletException;
  import javax.servlet.annotation.WebServlet;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.apache.http.HttpStatus;
  import org.eclipse.jgit.lfs.errors.InvalidLongObjectIdException;
  import org.eclipse.jgit.lfs.lib.AnyLongObjectId;
  import org.eclipse.jgit.lfs.lib.Constants;
  import org.eclipse.jgit.lfs.lib.LongObjectId;
  import org.eclipse.jgit.lfs.server.internal.LfsGson;
  import org.eclipse.jgit.lfs.server.internal.LfsServerText;
  
  /**
   * Servlet supporting upload and download of large objects as defined by the
   * GitHub Large File Storage extension API extending git to allow separate
   * storage of large files
   * (https://github.com/github/git-lfs/tree/master/docs/api).
   *
   * @since 4.3
   */
  @WebServlet(asyncSupported = true)
  public class FileLfsServlet extends HttpServlet {
  
  	private static final long serialVersionUID = 1L;
  
  	private final FileLfsRepository repository;
  
  	private final long timeout;
  
  	/**
  	 * <p>Constructor for FileLfsServlet.</p>
  	 *
  	 * @param repository
  	 *            the repository storing the large objects
  	 * @param timeout
  	 *            timeout for object upload / download in milliseconds
  	 */
  	public FileLfsServlet(FileLfsRepository repository, long timeout) {
  		this.repository = repository;
  		this.timeout = timeout;
  	}
  
  	/**
  	 * {@inheritDoc}
  	 *
  	 * Handle object downloads
  	 */
  	@Override
  	protected void doGet(HttpServletRequest req,
  			HttpServletResponse rsp) throws ServletException, IOException {
  		AnyLongObjectId obj = getObjectToTransfer(req, rsp);
  		if (obj != null) {
  			if (repository.getSize(obj) == -1) {
  				sendError(rsp, HttpStatus.SC_NOT_FOUND, MessageFormat
  						.format(LfsServerText.get().objectNotFound,
  								obj.getName()));
  				return;
  			}
  			AsyncContext context = req.startAsync();
  			context.setTimeout(timeout);
  			rsp.getOutputStream()
  					.setWriteListener(new ObjectDownloadListener(repository,
  							context, rsp, obj));
  		}
  	}
  
  	/**
  	 * Retrieve object id from request
  	 *
  	 * @param req
  	 *            servlet request
  	 * @param rsp
  	 *            servlet response
  	 * @return object id, or <code>null</code> if the object id could not be
  	 *         retrieved
  	 * @throws java.io.IOException
  	 *             if an I/O error occurs
  	 * @since 4.6
  	 */
  	protected AnyLongObjectId getObjectToTransfer(HttpServletRequest req,
  			HttpServletResponse rsp) throws IOException {
 		String info = req.getPathInfo();
 		int length = 1 + Constants.LONG_OBJECT_ID_STRING_LENGTH;
 		if (info.length() != length) {
 			sendError(rsp, HttpStatus.SC_UNPROCESSABLE_ENTITY, MessageFormat
 					.format(LfsServerText.get().invalidPathInfo, info));
 			return null;
 		}
 		try {
 			return LongObjectId.fromString(info.substring(1, length));
 		} catch (InvalidLongObjectIdException e) {
 			sendError(rsp, HttpStatus.SC_UNPROCESSABLE_ENTITY, e.getMessage());
 			return null;
 		}
 	}
 
 	/**
 	 * {@inheritDoc}
 	 *
 	 * Handle object uploads
 	 */
 	@Override
 	protected void doPut(HttpServletRequest req,
 			HttpServletResponse rsp) throws ServletException, IOException {
 		AnyLongObjectId id = getObjectToTransfer(req, rsp);
 		if (id != null) {
 			AsyncContext context = req.startAsync();
 			context.setTimeout(timeout);
 			req.getInputStream().setReadListener(new ObjectUploadListener(
 					repository, context, req, rsp, id));
 		}
 	}
 
 	/**
 	 * Send an error response.
 	 *
 	 * @param rsp
 	 *            the servlet response
 	 * @param status
 	 *            HTTP status code
 	 * @param message
 	 *            error message
 	 * @throws java.io.IOException
 	 *             on failure to send the response
 	 * @since 4.6
 	 */
 	protected static void sendError(HttpServletResponse rsp, int status, String message)
 			throws IOException {
 		if (rsp.isCommitted()) {
 			rsp.getOutputStream().close();
 			return;
 		}
 		rsp.reset();
 		rsp.setStatus(status);
 		try (PrintWriter writer = rsp.getWriter()) {
 			LfsGson.toJson(message, writer);
 			writer.flush();
 		}
 		rsp.flushBuffer();
 	}
 }