/*
 * 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 java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLConnection;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.TreeMap;

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 Amazon S3 protocol.

This transport communicates with the Amazon S3 servers (a non-free commercial
hosting service that users must subscribe to). Some users may find transport
to and from S3 to be a useful backup service.

The transport does not require any specialized Git support on the remote
(server side) repository, as Amazon does not provide any such support.
Repository files are retrieved directly through the S3 API, which uses
extended HTTP/1.1 semantics. This make it possible to read or write Git data
from a remote repository that is stored on S3.
 Unlike the HTTP variant (see TransportHttp) we rely upon being able to list objects in a bucket, as the S3 API supports this function. By listing the bucket contents we can avoid relying on objects/info/packs
or info/refs in the remote repository.

Concurrent pushing over this transport is not supported. Multiple concurrent
push operations may cause confusion in the repository state.
See Also:
WalkFetchConnection
WalkPushConnection/**
 * Transport over the non-Git aware Amazon S3 protocol.
 * <p>
 * This transport communicates with the Amazon S3 servers (a non-free commercial
 * hosting service that users must subscribe to). Some users may find transport
 * to and from S3 to be a useful backup service.
 * <p>
 * The transport does not require any specialized Git support on the remote
 * (server side) repository, as Amazon does not provide any such support.
 * Repository files are retrieved directly through the S3 API, which uses
 * extended HTTP/1.1 semantics. This make it possible to read or write Git data
 * from a remote repository that is stored on S3.
 * <p>
 * Unlike the HTTP variant (see
 * {@link org.eclipse.jgit.transport.TransportHttp}) we rely upon being able to
 * list objects in a bucket, as the S3 API supports this function. By listing
 * the bucket contents we can avoid relying on <code>objects/info/packs</code>
 * or <code>info/refs</code> in the remote repository.
 * <p>
 * Concurrent pushing over this transport is not supported. Multiple concurrent
 * push operations may cause confusion in the repository state.
 *
 * @see WalkFetchConnection
 * @see WalkPushConnection
 */
public class TransportAmazonS3 extends HttpTransport implements WalkTransport {
	static final String S3_SCHEME = "amazon-s3"; //$NON-NLS-1$

	static final TransportProtocol PROTO_S3 = new TransportProtocol() {
		@Override
		public String getName() {
			return "Amazon S3"; //$NON-NLS-1$
		}

		@Override
		public Set<String> getSchemes() {
			return Collections.singleton(S3_SCHEME);
		}

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

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

		@Override
		public Transport open(URIish uri, Repository local, String remoteName)
				throws NotSupportedException {
			return new TransportAmazonS3(local, uri);
		}
	};

	
User information necessary to connect to S3. /** User information necessary to connect to S3. */
	final AmazonS3 s3;

	
Bucket the remote repository is stored in. /** Bucket the remote repository is stored in. */
	final String bucket;

	
Key prefix which all objects related to the repository start with.

The prefix does not start with "/".

The prefix does not end with "/". The trailing slash is stripped during
the constructor if a trailing slash was supplied in the URIish.

All files within the remote repository start with
keyPrefix + "/".
/**
	 * Key prefix which all objects related to the repository start with.
	 * <p>
	 * The prefix does not start with "/".
	 * <p>
	 * The prefix does not end with "/". The trailing slash is stripped during
	 * the constructor if a trailing slash was supplied in the URIish.
	 * <p>
	 * All files within the remote repository start with
	 * <code>keyPrefix + "/"</code>.
	 */
	private final String keyPrefix;

	TransportAmazonS3(final Repository local, final URIish uri)
			throws NotSupportedException {
		super(local, uri);

		Properties props = loadProperties();
		File directory = local.getDirectory();
		if (!props.containsKey("tmpdir") && directory != null) //$NON-NLS-1$
			props.put("tmpdir", directory.getPath()); //$NON-NLS-1$

		s3 = new AmazonS3(props);
		bucket = uri.getHost();

		String p = uri.getPath();
		if (p.startsWith("/")) //$NON-NLS-1$
			p = p.substring(1);
		if (p.endsWith("/")) //$NON-NLS-1$
			p = p.substring(0, p.length() - 1);
		keyPrefix = p;
	}

	private Properties loadProperties() throws NotSupportedException {
		if (local.getDirectory() != null) {
			File propsFile = new File(local.getDirectory(), uri.getUser());
			if (propsFile.isFile())
				return loadPropertiesFile(propsFile);
		}

		File propsFile = new File(local.getFS().userHome(), uri.getUser());
		if (propsFile.isFile())
			return loadPropertiesFile(propsFile);

		Properties props = new Properties();
		String user = uri.getUser();
		String pass = uri.getPass();
		if (user != null && pass != null) {
		        props.setProperty("accesskey", user); //$NON-NLS-1$
		        props.setProperty("secretkey", pass); //$NON-NLS-1$
		} else
			throw new NotSupportedException(MessageFormat.format(
					JGitText.get().cannotReadFile, propsFile));
		return props;
	}

	private static Properties loadPropertiesFile(File propsFile)
			throws NotSupportedException {
		try {
			return AmazonS3.properties(propsFile);
		} catch (IOException e) {
			throw new NotSupportedException(MessageFormat.format(
					JGitText.get().cannotReadFile, propsFile), e);
		}
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public FetchConnection openFetch() throws TransportException {
		final DatabaseS3 c = new DatabaseS3(bucket, keyPrefix + "/objects"); //$NON-NLS-1$
		final WalkFetchConnection r = new WalkFetchConnection(this, c);
		r.available(c.readAdvertisedRefs());
		return r;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public PushConnection openPush() throws TransportException {
		final DatabaseS3 c = new DatabaseS3(bucket, keyPrefix + "/objects"); //$NON-NLS-1$
		final WalkPushConnection r = new WalkPushConnection(this, c);
		r.available(c.readAdvertisedRefs());
		return r;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public void close() {
		// No explicit connections are maintained.
	}

	class DatabaseS3 extends WalkRemoteObjectDatabase {
		private final String bucketName;

		private final String objectsKey;

		DatabaseS3(final String b, final String o) {
			bucketName = b;
			objectsKey = o;
		}

		private String resolveKey(String subpath) {
			if (subpath.endsWith("/")) //$NON-NLS-1$
				subpath = subpath.substring(0, subpath.length() - 1);
			String k = objectsKey;
			while (subpath.startsWith(ROOT_DIR)) {
				k = k.substring(0, k.lastIndexOf('/'));
				subpath = subpath.substring(3);
			}
			return k + "/" + subpath; //$NON-NLS-1$
		}

		@Override
		URIish getURI() {
			URIish u = new URIish();
			u = u.setScheme(S3_SCHEME);
			u = u.setHost(bucketName);
			u = u.setPath("/" + objectsKey); //$NON-NLS-1$
			return u;
		}

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

		@Override
		WalkRemoteObjectDatabase openAlternate(String location)
				throws IOException {
			return new DatabaseS3(bucketName, resolveKey(location));
		}

		@Override
		Collection<String> getPackNames() throws IOException {
			final HashSet<String> have = new HashSet<>();
			have.addAll(s3.list(bucket, resolveKey("pack"))); //$NON-NLS-1$

			final Collection<String> packs = new ArrayList<>();
			for (String n : have) {
				if (!n.startsWith("pack-") || !n.endsWith(".pack")) //$NON-NLS-1$ //$NON-NLS-2$
					continue;

				final String in = n.substring(0, n.length() - 5) + ".idx"; //$NON-NLS-1$
				if (have.contains(in))
					packs.add(n);
			}
			return packs;
		}

		@Override
		FileStream open(String path) throws IOException {
			final URLConnection c = s3.get(bucket, resolveKey(path));
			final InputStream raw = c.getInputStream();
			final InputStream in = s3.decrypt(c);
			final int len = c.getContentLength();
			return new FileStream(in, raw == in ? len : -1);
		}

		@Override
		void deleteFile(String path) throws IOException {
			s3.delete(bucket, resolveKey(path));
		}

		@Override
		OutputStream writeFile(final String path,
				final ProgressMonitor monitor, final String monitorTask)
				throws IOException {
			return s3.beginPut(bucket, resolveKey(path), monitor, monitorTask);
		}

		@Override
		void writeFile(String path, byte[] data) throws IOException {
			s3.put(bucket, resolveKey(path), data);
		}

		Map<String, Ref> readAdvertisedRefs() throws TransportException {
			final TreeMap<String, Ref> avail = new TreeMap<>();
			readPackedRefs(avail);
			readLooseRefs(avail);
			readRef(avail, Constants.HEAD);
			return avail;
		}

		private void readLooseRefs(TreeMap<String, Ref> avail)
				throws TransportException {
			try {
				for (final String n : s3.list(bucket, resolveKey(ROOT_DIR
						+ "refs"))) //$NON-NLS-1$
					readRef(avail, "refs/" + n); //$NON-NLS-1$
			} catch (IOException e) {
				throw new TransportException(getURI(), JGitText.get().cannotListRefs, e);
			}
		}

		private Ref readRef(TreeMap<String, Ref> avail, String rn)
				throws TransportException {
			final String s;
			String ref = ROOT_DIR + rn;
			try {
				try (BufferedReader br = openReader(ref)) {
					s = br.readLine();
				}
			} catch (FileNotFoundException noRef) {
				return null;
			} catch (IOException err) {
				throw new TransportException(getURI(), MessageFormat.format(
						JGitText.get().transportExceptionReadRef, ref), err);
			}

			if (s == null)
				throw new TransportException(getURI(), MessageFormat.format(JGitText.get().transportExceptionEmptyRef, rn));

			if (s.startsWith("ref: ")) { //$NON-NLS-1$
				final String target = s.substring("ref: ".length()); //$NON-NLS-1$
				Ref r = avail.get(target);
				if (r == null)
					r = readRef(avail, target);
				if (r == null)
					r = new ObjectIdRef.Unpeeled(Ref.Storage.NEW, target, null);
				r = new SymbolicRef(rn, r);
				avail.put(r.getName(), r);
				return r;
			}

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

			throw new TransportException(getURI(), MessageFormat.format(JGitText.get().transportExceptionBadRef, rn, s));
		}

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

		@Override
		void close() {
			// We do not maintain persistent connections.
		}
	}
}