/*
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.transport;

import static org.eclipse.jgit.lib.Constants.INFO_ALTERNATES;
import static org.eclipse.jgit.lib.Constants.LOCK_SUFFIX;
import static org.eclipse.jgit.lib.Constants.OBJECTS;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;

import org.eclipse.jgit.errors.NotSupportedException;
import org.eclipse.jgit.errors.TransportException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectIdRef;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Ref.Storage;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.lib.SymbolicRef;

Transport over the non-Git aware SFTP (SSH based FTP) protocol.

The SFTP transport does not require any specialized Git support on the remote
(server side) repository. Object files are retrieved directly through secure
shell's FTP protocol, making it possible to copy objects from a remote
repository that is available over SSH, but whose remote host does not have
Git installed.
 Unlike the HTTP variant (see TransportHttp) we rely upon being able to list files in directories, as the SFTP protocol supports this function. By listing files through SFTP we can avoid needing to have current objects/info/packs or info/refs files on the remote
repository and access the data directly, much as Git itself would.

Concurrent pushing over this transport is not supported. Multiple concurrent
push operations may cause confusion in the repository state.
See Also:
WalkFetchConnection/**
 * Transport over the non-Git aware SFTP (SSH based FTP) protocol.
 * <p>
 * The SFTP transport does not require any specialized Git support on the remote
 * (server side) repository. Object files are retrieved directly through secure
 * shell's FTP protocol, making it possible to copy objects from a remote
 * repository that is available over SSH, but whose remote host does not have
 * Git installed.
 * <p>
 * Unlike the HTTP variant (see
 * {@link org.eclipse.jgit.transport.TransportHttp}) we rely upon being able to
 * list files in directories, as the SFTP protocol supports this function. By
 * listing files through SFTP we can avoid needing to have current
 * <code>objects/info/packs</code> or <code>info/refs</code> files on the remote
 * repository and access the data directly, much as Git itself would.
 * <p>
 * Concurrent pushing over this transport is not supported. Multiple concurrent
 * push operations may cause confusion in the repository state.
 *
 * @see WalkFetchConnection
 */
public class TransportSftp extends SshTransport implements WalkTransport {
	static final TransportProtocol PROTO_SFTP = new TransportProtocol() {
		@Override
		public String getName() {
			return JGitText.get().transportProtoSFTP;
		}

		@Override
		public Set<String> getSchemes() {
			return Collections.singleton("sftp"); //$NON-NLS-1$
		}

		@Override
		public Set<URIishField> getRequiredFields() {
			return Collections.unmodifiableSet(EnumSet.of(URIishField.HOST,
					URIishField.PATH));
		}

		@Override
		public Set<URIishField> getOptionalFields() {
			return Collections.unmodifiableSet(EnumSet.of(URIishField.USER,
					URIishField.PASS, URIishField.PORT));
		}

		@Override
		public int getDefaultPort() {
			return 22;
		}

		@Override
		public Transport open(URIish uri, Repository local, String remoteName)
				throws NotSupportedException {
			return new TransportSftp(local, uri);
		}
	};

	TransportSftp(Repository local, URIish uri) {
		super(local, uri);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public FetchConnection openFetch() throws TransportException {
		final SftpObjectDB c = new SftpObjectDB(uri.getPath());
		final WalkFetchConnection r = new WalkFetchConnection(this, c);
		r.available(c.readAdvertisedRefs());
		return r;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public PushConnection openPush() throws TransportException {
		final SftpObjectDB c = new SftpObjectDB(uri.getPath());
		final WalkPushConnection r = new WalkPushConnection(this, c);
		r.available(c.readAdvertisedRefs());
		return r;
	}

	FtpChannel newSftp() throws IOException {
		FtpChannel channel = getSession().getFtpChannel();
		channel.connect(getTimeout(), TimeUnit.SECONDS);
		return channel;
	}

	class SftpObjectDB extends WalkRemoteObjectDatabase {
		private final String objectsPath;

		private FtpChannel ftp;

		SftpObjectDB(String path) throws TransportException {
			if (path.startsWith("/~")) //$NON-NLS-1$
				path = path.substring(1);
			if (path.startsWith("~/")) //$NON-NLS-1$
				path = path.substring(2);
			try {
				ftp = newSftp();
				ftp.cd(path);
				ftp.cd(OBJECTS);
				objectsPath = ftp.pwd();
			} catch (FtpChannel.FtpException f) {
				throw new TransportException(MessageFormat.format(
						JGitText.get().cannotEnterObjectsPath, path,
						f.getMessage()), f);
			} catch (IOException ioe) {
				close();
				throw new TransportException(uri, ioe.getMessage(), ioe);
			}
		}

		SftpObjectDB(SftpObjectDB parent, String p)
				throws TransportException {
			try {
				ftp = newSftp();
				ftp.cd(parent.objectsPath);
				ftp.cd(p);
				objectsPath = ftp.pwd();
			} catch (FtpChannel.FtpException f) {
				throw new TransportException(MessageFormat.format(
						JGitText.get().cannotEnterPathFromParent, p,
						parent.objectsPath, f.getMessage()), f);
			} catch (IOException ioe) {
				close();
				throw new TransportException(uri, ioe.getMessage(), ioe);
			}
		}

		@Override
		URIish getURI() {
			return uri.setPath(objectsPath);
		}

		@Override
		Collection<WalkRemoteObjectDatabase> getAlternates() throws IOException {
			try {
				return readAlternates(INFO_ALTERNATES);
			} catch (FileNotFoundException err) {
				return null;
			}
		}

		@Override
		WalkRemoteObjectDatabase openAlternate(String location)
				throws IOException {
			return new SftpObjectDB(this, location);
		}

		@Override
		Collection<String> getPackNames() throws IOException {
			final List<String> packs = new ArrayList<>();
			try {
				Collection<FtpChannel.DirEntry> list = ftp.ls("pack"); //$NON-NLS-1$
				Set<String> files = list.stream()
						.map(FtpChannel.DirEntry::getFilename)
						.collect(Collectors.toSet());
				HashMap<String, Long> mtimes = new HashMap<>();

				for (FtpChannel.DirEntry ent : list) {
					String n = ent.getFilename();
					if (!n.startsWith("pack-") || !n.endsWith(".pack")) { //$NON-NLS-1$ //$NON-NLS-2$
						continue;
					}
					String in = n.substring(0, n.length() - 5) + ".idx"; //$NON-NLS-1$
					if (!files.contains(in)) {
						continue;
					}
					mtimes.put(n, Long.valueOf(ent.getModifiedTime()));
					packs.add(n);
				}

				Collections.sort(packs,
						(o1, o2) -> mtimes.get(o2).compareTo(mtimes.get(o1)));
			} catch (FtpChannel.FtpException f) {
				throw new TransportException(
						MessageFormat.format(JGitText.get().cannotListPackPath,
								objectsPath, f.getMessage()),
						f);
			}
			return packs;
		}

		@Override
		FileStream open(String path) throws IOException {
			try {
				return new FileStream(ftp.get(path));
			} catch (FtpChannel.FtpException f) {
				if (f.getStatus() == FtpChannel.FtpException.NO_SUCH_FILE) {
					throw new FileNotFoundException(path);
				}
				throw new TransportException(MessageFormat.format(
						JGitText.get().cannotGetObjectsPath, objectsPath, path,
						f.getMessage()), f);
			}
		}

		@Override
		void deleteFile(String path) throws IOException {
			try {
				ftp.delete(path);
			} catch (FtpChannel.FtpException f) {
				throw new TransportException(MessageFormat.format(
						JGitText.get().cannotDeleteObjectsPath, objectsPath,
						path, f.getMessage()), f);
			}

			// Prune any now empty directories.
			//
			String dir = path;
			int s = dir.lastIndexOf('/');
			while (s > 0) {
				try {
					dir = dir.substring(0, s);
					ftp.rmdir(dir);
					s = dir.lastIndexOf('/');
				} catch (IOException je) {
					// If we cannot delete it, leave it alone. It may have
					// entries still in it, or maybe we lack write access on
					// the parent. Either way it isn't a fatal error.
					//
					break;
				}
			}
		}

		@Override
		OutputStream writeFile(String path, ProgressMonitor monitor,
				String monitorTask) throws IOException {
			Throwable err = null;
			try {
				return ftp.put(path);
			} catch (FileNotFoundException e) {
				mkdir_p(path);
			} catch (FtpChannel.FtpException je) {
				if (je.getStatus() == FtpChannel.FtpException.NO_SUCH_FILE) {
					mkdir_p(path);
				} else {
					err = je;
				}
			}
			if (err == null) {
				try {
					return ftp.put(path);
				} catch (IOException e) {
					err = e;
				}
			}
			throw new TransportException(
					MessageFormat.format(JGitText.get().cannotWriteObjectsPath,
							objectsPath, path, err.getMessage()),
					err);
		}

		@Override
		void writeFile(String path, byte[] data) throws IOException {
			final String lock = path + LOCK_SUFFIX;
			try {
				super.writeFile(lock, data);
				try {
					ftp.rename(lock, path);
				} catch (IOException e) {
					throw new TransportException(MessageFormat.format(
							JGitText.get().cannotWriteObjectsPath, objectsPath,
							path, e.getMessage()), e);
				}
			} catch (IOException err) {
				try {
					ftp.rm(lock);
				} catch (IOException e) {
					// Ignore deletion failure, we are already
					// failing anyway.
				}
				throw err;
			}
		}

		private void mkdir_p(String path) throws IOException {
			final int s = path.lastIndexOf('/');
			if (s <= 0)
				return;

			path = path.substring(0, s);
			Throwable err = null;
			try {
				ftp.mkdir(path);
				return;
			} catch (FileNotFoundException f) {
				mkdir_p(path);
			} catch (FtpChannel.FtpException je) {
				if (je.getStatus() == FtpChannel.FtpException.NO_SUCH_FILE) {
					mkdir_p(path);
				} else {
					err = je;
				}
			}
			if (err == null) {
				try {
					ftp.mkdir(path);
					return;
				} catch (IOException e) {
					err = e;
				}
			}
			throw new TransportException(MessageFormat.format(
						JGitText.get().cannotMkdirObjectPath, objectsPath, path,
					err.getMessage()), err);
		}

		Map<String, Ref> readAdvertisedRefs() throws TransportException {
			final TreeMap<String, Ref> avail = new TreeMap<>();
			readPackedRefs(avail);
			readRef(avail, ROOT_DIR + Constants.HEAD, Constants.HEAD);
			readLooseRefs(avail, ROOT_DIR + "refs", "refs/"); //$NON-NLS-1$ //$NON-NLS-2$
			return avail;
		}

		private void readLooseRefs(TreeMap<String, Ref> avail, String dir,
				String prefix) throws TransportException {
			final Collection<FtpChannel.DirEntry> list;
			try {
				list = ftp.ls(dir);
			} catch (IOException e) {
				throw new TransportException(MessageFormat.format(
						JGitText.get().cannotListObjectsPath, objectsPath, dir,
						e.getMessage()), e);
			}

			for (FtpChannel.DirEntry ent : list) {
				String n = ent.getFilename();
				if (".".equals(n) || "..".equals(n)) //$NON-NLS-1$ //$NON-NLS-2$
					continue;

				String nPath = dir + "/" + n; //$NON-NLS-1$
				if (ent.isDirectory()) {
					readLooseRefs(avail, nPath, prefix + n + "/"); //$NON-NLS-1$
				} else {
					readRef(avail, nPath, prefix + n);
				}
			}
		}

		private Ref readRef(TreeMap<String, Ref> avail, String path,
				String name) throws TransportException {
			final String line;
			try (BufferedReader br = openReader(path)) {
				line = br.readLine();
			} catch (FileNotFoundException noRef) {
				return null;
			} catch (IOException err) {
				throw new TransportException(MessageFormat.format(
						JGitText.get().cannotReadObjectsPath, objectsPath, path,
						err.getMessage()), err);
			}

			if (line == null) {
				throw new TransportException(
						MessageFormat.format(JGitText.get().emptyRef, name));
			}
			if (line.startsWith("ref: ")) { //$NON-NLS-1$
				final String target = line.substring("ref: ".length()); //$NON-NLS-1$
				Ref r = avail.get(target);
				if (r == null)
					r = readRef(avail, ROOT_DIR + target, target);
				if (r == null)
					r = new ObjectIdRef.Unpeeled(Ref.Storage.NEW, target, null);
				r = new SymbolicRef(name, r);
				avail.put(r.getName(), r);
				return r;
			}

			if (ObjectId.isId(line)) {
				final Ref r = new ObjectIdRef.Unpeeled(loose(avail.get(name)),
						name, ObjectId.fromString(line));
				avail.put(r.getName(), r);
				return r;
			}

			throw new TransportException(
					MessageFormat.format(JGitText.get().badRef, name, line));
		}

		private Storage loose(Ref r) {
			if (r != null && r.getStorage() == Storage.PACKED) {
				return Storage.LOOSE_PACKED;
			}
			return Storage.LOOSE;
		}

		@Override
		void close() {
			if (ftp != null) {
				try {
					if (ftp.isConnected()) {
						ftp.disconnect();
					}
				} finally {
					ftp = null;
				}
			}
		}
	}
}