/*
    * Copyright (C) 2011, Google Inc. 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.http.server;
  
  import static javax.servlet.http.HttpServletResponse.SC_FORBIDDEN;
  import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
  import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
  import static org.eclipse.jgit.http.server.ServletUtils.ATTRIBUTE_HANDLER;
  import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_SIDE_BAND_64K;
  import static org.eclipse.jgit.transport.SideBandOutputStream.CH_ERROR;
  import static org.eclipse.jgit.transport.SideBandOutputStream.SMALL_BUF;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.eclipse.jgit.internal.transport.parser.FirstCommand;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.transport.PacketLineIn;
  import org.eclipse.jgit.transport.PacketLineOut;
  import org.eclipse.jgit.transport.ReceivePack;
  import org.eclipse.jgit.transport.RequestNotYetReadException;
  import org.eclipse.jgit.transport.SideBandOutputStream;
  
  /**
   * Utility functions for handling the Git-over-HTTP protocol.
   */
  public class GitSmartHttpTools {
  	private static final String INFO_REFS = Constants.INFO_REFS;
  
  	/** Name of the git-upload-pack service. */
  	public static final String UPLOAD_PACK = "git-upload-pack";
  
  	/** Name of the git-receive-pack service. */
  	public static final String RECEIVE_PACK = "git-receive-pack";
  
  	/** Content type supplied by the client to the /git-upload-pack handler. */
  	public static final String UPLOAD_PACK_REQUEST_TYPE =
  			"application/x-git-upload-pack-request";
  
  	/** Content type returned from the /git-upload-pack handler. */
  	public static final String UPLOAD_PACK_RESULT_TYPE =
  			"application/x-git-upload-pack-result";
  
  	/** Content type supplied by the client to the /git-receive-pack handler. */
  	public static final String RECEIVE_PACK_REQUEST_TYPE =
  			"application/x-git-receive-pack-request";
  
  	/** Content type returned from the /git-receive-pack handler. */
  	public static final String RECEIVE_PACK_RESULT_TYPE =
  			"application/x-git-receive-pack-result";
  
  	/** Git service names accepted by the /info/refs?service= handler. */
  	public static final List<String> VALID_SERVICES =
  			Collections.unmodifiableList(Arrays.asList(new String[] {
  					UPLOAD_PACK, RECEIVE_PACK }));
  
  	private static final String INFO_REFS_PATH = "/" + INFO_REFS;
  	private static final String UPLOAD_PACK_PATH = "/" + UPLOAD_PACK;
  	private static final String RECEIVE_PACK_PATH = "/" + RECEIVE_PACK;
  
  	private static final List<String> SERVICE_SUFFIXES =
  			Collections.unmodifiableList(Arrays.asList(new String[] {
  					INFO_REFS_PATH, UPLOAD_PACK_PATH, RECEIVE_PACK_PATH }));
  
  	/**
  	 * Check a request for Git-over-HTTP indicators.
  	 *
  	 * @param req
  	 *            the current HTTP request that may have been made by Git.
  	 * @return true if the request is likely made by a Git client program.
  	 */
  	public static boolean isGitClient(HttpServletRequest req) {
  		return isInfoRefs(req) || isUploadPack(req) || isReceivePack(req);
  	}
  
  	/**
  	 * Send an error to the Git client or browser.
  	 * <p>
  	 * Server implementors may use this method to send customized error messages
  	 * to a Git protocol client using an HTTP 200 OK response with the error
  	 * embedded in the payload. If the request was not issued by a Git client,
  	 * an HTTP response code is returned instead.
  	 *
  	 * @param req
 	 *            current request.
 	 * @param res
 	 *            current response.
 	 * @param httpStatus
 	 *            HTTP status code to set if the client is not a Git client.
 	 * @throws IOException
 	 *             the response cannot be sent.
 	 */
 	public static void sendError(HttpServletRequest req,
 			HttpServletResponse res, int httpStatus) throws IOException {
 		sendError(req, res, httpStatus, null);
 	}
 
 	/**
 	 * Send an error to the Git client or browser.
 	 * <p>
 	 * Server implementors may use this method to send customized error messages
 	 * to a Git protocol client using an HTTP 200 OK response with the error
 	 * embedded in the payload. If the request was not issued by a Git client,
 	 * an HTTP response code is returned instead.
 	 * <p>
 	 * This method may only be called before handing off the request to
 	 * {@link org.eclipse.jgit.transport.UploadPack#upload(java.io.InputStream, OutputStream, OutputStream)}
 	 * or
 	 * {@link org.eclipse.jgit.transport.ReceivePack#receive(java.io.InputStream, OutputStream, OutputStream)}.
 	 *
 	 * @param req
 	 *            current request.
 	 * @param res
 	 *            current response.
 	 * @param httpStatus
 	 *            HTTP status code to set if the client is not a Git client.
 	 * @param textForGit
 	 *            plain text message to display on the user's console. This is
 	 *            shown only if the client is likely to be a Git client. If null
 	 *            or the empty string a default text is chosen based on the HTTP
 	 *            response code.
 	 * @throws IOException
 	 *             the response cannot be sent.
 	 */
 	public static void sendError(HttpServletRequest req,
 			HttpServletResponse res, int httpStatus, String textForGit)
 			throws IOException {
 		if (textForGit == null || textForGit.length() == 0) {
 			switch (httpStatus) {
 			case SC_FORBIDDEN:
 				textForGit = HttpServerText.get().repositoryAccessForbidden;
 				break;
 			case SC_NOT_FOUND:
 				textForGit = HttpServerText.get().repositoryNotFound;
 				break;
 			case SC_INTERNAL_SERVER_ERROR:
 				textForGit = HttpServerText.get().internalServerError;
 				break;
 			default:
 				textForGit = "HTTP " + httpStatus;
 				break;
 			}
 		}
 
 		if (isInfoRefs(req)) {
 			sendInfoRefsError(req, res, textForGit, httpStatus);
 		} else if (isUploadPack(req)) {
 			sendUploadPackError(req, res, textForGit, httpStatus);
 		} else if (isReceivePack(req)) {
 			sendReceivePackError(req, res, textForGit, httpStatus);
 		} else {
 			if (httpStatus < 400)
 				ServletUtils.consumeRequestBody(req);
 			res.sendError(httpStatus, textForGit);
 		}
 	}
 
 	private static void sendInfoRefsError(HttpServletRequest req,
 			HttpServletResponse res, String textForGit, int httpStatus)
 			throws IOException {
 		ByteArrayOutputStream buf = new ByteArrayOutputStream(128);
 		PacketLineOut pck = new PacketLineOut(buf);
 		String svc = req.getParameter("service");
 		pck.writeString("# service=" + svc + "\n");
 		pck.end();
 		pck.writeString("ERR " + textForGit);
 		send(req, res, infoRefsResultType(svc), buf.toByteArray(), httpStatus);
 	}
 
 	private static void sendUploadPackError(HttpServletRequest req,
 			HttpServletResponse res, String textForGit, int httpStatus)
 			throws IOException {
 		// Do not use sideband. Sideband is acceptable only while packfile is
 		// being sent. Other places, like acknowledgement section, do not
 		// support sideband. Use an error packet.
 		ByteArrayOutputStream buf = new ByteArrayOutputStream(128);
 		PacketLineOut pckOut = new PacketLineOut(buf);
 		writePacket(pckOut, textForGit);
 		send(req, res, UPLOAD_PACK_RESULT_TYPE, buf.toByteArray(), httpStatus);
 	}
 
 	private static void sendReceivePackError(HttpServletRequest req,
 			HttpServletResponse res, String textForGit, int httpStatus)
 			throws IOException {
 		ByteArrayOutputStream buf = new ByteArrayOutputStream(128);
 		PacketLineOut pckOut = new PacketLineOut(buf);
 
 		boolean sideband;
 		ReceivePack rp = (ReceivePack) req.getAttribute(ATTRIBUTE_HANDLER);
 		if (rp != null) {
 			try {
 				sideband = rp.isSideBand();
 			} catch (RequestNotYetReadException e) {
 				sideband = isReceivePackSideBand(req);
 			}
 		} else
 			sideband = isReceivePackSideBand(req);
 
 		if (sideband)
 			writeSideBand(buf, textForGit);
 		else
 			writePacket(pckOut, textForGit);
 		send(req, res, RECEIVE_PACK_RESULT_TYPE, buf.toByteArray(), httpStatus);
 	}
 
 	private static boolean isReceivePackSideBand(HttpServletRequest req) {
 		try {
 			// The client may be in a state where they have sent the sideband
 			// capability and are expecting a response in the sideband, but we might
 			// not have a ReceivePack, or it might not have read any of the request.
 			// So, cheat and read the first line.
 			String line = new PacketLineIn(req.getInputStream()).readString();
 			FirstCommand parsed = FirstCommand.fromLine(line);
 			return parsed.getCapabilities().contains(CAPABILITY_SIDE_BAND_64K);
 		} catch (IOException e) {
 			// Probably the connection is closed and a subsequent write will fail, but
 			// try it just in case.
 			return false;
 		}
 	}
 
 	private static void writeSideBand(OutputStream out, String textForGit)
 			throws IOException {
 		try (OutputStream msg = new SideBandOutputStream(CH_ERROR, SMALL_BUF,
 				out)) {
 			msg.write(Constants.encode("error: " + textForGit));
 			msg.flush();
 		}
 	}
 
 	private static void writePacket(PacketLineOut pckOut, String textForGit)
 			throws IOException {
 		pckOut.writeString("ERR " + textForGit);
 	}
 
 	private static void send(HttpServletRequest req, HttpServletResponse res,
 			String type, byte[] buf, int httpStatus) throws IOException {
 		ServletUtils.consumeRequestBody(req);
 		res.setStatus(httpStatus);
 		res.setContentType(type);
 		res.setContentLength(buf.length);
 		try (OutputStream os = res.getOutputStream()) {
 			os.write(buf);
 		}
 	}
 
 	/**
 	 * Get the response Content-Type a client expects for the request.
 	 * <p>
 	 * This method should only be invoked if
 	 * {@link #isGitClient(HttpServletRequest)} is true.
 	 *
 	 * @param req
 	 *            current request.
 	 * @return the Content-Type the client expects.
 	 * @throws IllegalArgumentException
 	 *             the request is not a Git client request. See
 	 *             {@link #isGitClient(HttpServletRequest)}.
 	 */
 	public static String getResponseContentType(HttpServletRequest req) {
 		if (isInfoRefs(req))
 			return infoRefsResultType(req.getParameter("service"));
 		else if (isUploadPack(req))
 			return UPLOAD_PACK_RESULT_TYPE;
 		else if (isReceivePack(req))
 			return RECEIVE_PACK_RESULT_TYPE;
 		else
 			throw new IllegalArgumentException();
 	}
 
 	static String infoRefsResultType(String svc) {
 		return "application/x-" + svc + "-advertisement";
 	}
 
 	/**
 	 * Strip the Git service suffix from a request path.
 	 *
 	 * Generally the suffix is stripped by the {@code SuffixPipeline} handling
 	 * the request, so this method is rarely needed.
 	 *
 	 * @param path
 	 *            the path of the request.
 	 * @return the path up to the last path component before the service suffix;
 	 *         the path as-is if it contains no service suffix.
 	 */
 	public static String stripServiceSuffix(String path) {
 		for (String suffix : SERVICE_SUFFIXES) {
 			if (path.endsWith(suffix))
 				return path.substring(0, path.length() - suffix.length());
 		}
 		return path;
 	}
 
 	/**
 	 * Check if the HTTP request was for the /info/refs?service= Git handler.
 	 *
 	 * @param req
 	 *            current request.
 	 * @return true if the request is for the /info/refs service.
 	 */
 	public static boolean isInfoRefs(HttpServletRequest req) {
 		return req.getRequestURI().endsWith(INFO_REFS_PATH)
 				&& VALID_SERVICES.contains(req.getParameter("service"));
 	}
 
 	/**
 	 * Check if the HTTP request path ends with the /git-upload-pack handler.
 	 *
 	 * @param pathOrUri
 	 *            path or URI of the request.
 	 * @return true if the request is for the /git-upload-pack handler.
 	 */
 	public static boolean isUploadPack(String pathOrUri) {
 		return pathOrUri != null && pathOrUri.endsWith(UPLOAD_PACK_PATH);
 	}
 
 	/**
 	 * Check if the HTTP request was for the /git-upload-pack Git handler.
 	 *
 	 * @param req
 	 *            current request.
 	 * @return true if the request is for the /git-upload-pack handler.
 	 */
 	public static boolean isUploadPack(HttpServletRequest req) {
 		return isUploadPack(req.getRequestURI())
 				&& UPLOAD_PACK_REQUEST_TYPE.equals(req.getContentType());
 	}
 
 	/**
 	 * Check if the HTTP request was for the /git-receive-pack Git handler.
 	 *
 	 * @param req
 	 *            current request.
 	 * @return true if the request is for the /git-receive-pack handler.
 	 */
 	public static boolean isReceivePack(HttpServletRequest req) {
 		String uri = req.getRequestURI();
 		return uri != null && uri.endsWith(RECEIVE_PACK_PATH)
 				&& RECEIVE_PACK_REQUEST_TYPE.equals(req.getContentType());
 	}
 
 	private GitSmartHttpTools() {
 	}
 }