/*
 * Copyright (C) 2016, Christian Halstrick <christian.halstrick@sap.com>
 * 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.lfs;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import org.eclipse.jgit.attributes.FilterCommand;
import org.eclipse.jgit.attributes.FilterCommandFactory;
import org.eclipse.jgit.attributes.FilterCommandRegistry;
import org.eclipse.jgit.lfs.internal.LfsConnectionFactory;
import org.eclipse.jgit.lfs.internal.LfsText;
import org.eclipse.jgit.lfs.lib.AnyLongObjectId;
import org.eclipse.jgit.lfs.lib.Constants;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.transport.http.HttpConnection;
import org.eclipse.jgit.util.HttpSupport;

import com.google.gson.Gson;
import com.google.gson.stream.JsonReader;

/**
 * Built-in LFS smudge filter
 *
 * When content is read from git's object-database and written to the filesystem
 * and this filter is configured for that content, then this filter will replace
 * the content of LFS pointer files with the original content. This happens e.g.
 * when a checkout needs to update a working tree file which is under LFS
 * control.
 *
 * @since 4.6
 */
public class SmudgeFilter extends FilterCommand {

	/**
	 * Max number of bytes to copy in a single {@link #run()} call.
	 */
	private static final int MAX_COPY_BYTES = 1024 * 1024 * 256;

	/**
	 * The factory is responsible for creating instances of
	 * {@link org.eclipse.jgit.lfs.SmudgeFilter}
	 */
	public final static FilterCommandFactory FACTORY = new FilterCommandFactory() {
		@Override
		public FilterCommand create(Repository db, InputStream in,
				OutputStream out) throws IOException {
			return new SmudgeFilter(db, in, out);
		}
	};

	/**
	 * Register this filter in JGit
	 */
	static void register() {
		FilterCommandRegistry
				.register(org.eclipse.jgit.lib.Constants.BUILTIN_FILTER_PREFIX
						+ Constants.ATTR_FILTER_DRIVER_PREFIX
						+ org.eclipse.jgit.lib.Constants.ATTR_FILTER_TYPE_SMUDGE,
						FACTORY);
	}

	/**
	 * Constructor for SmudgeFilter.
	 *
	 * @param db
	 *            a {@link org.eclipse.jgit.lib.Repository} object.
	 * @param in
	 *            a {@link java.io.InputStream} object. The stream is closed in
	 *            any case.
	 * @param out
	 *            a {@link java.io.OutputStream} object.
	 * @throws java.io.IOException
	 *             in case of an error
	 */
	public SmudgeFilter(Repository db, InputStream in, OutputStream out)
			throws IOException {
		super(in, out);
		try {
			Lfs lfs = new Lfs(db);
			LfsPointer res = LfsPointer.parseLfsPointer(in);
			if (res != null) {
				AnyLongObjectId oid = res.getOid();
				Path mediaFile = lfs.getMediaFile(oid);
				if (!Files.exists(mediaFile)) {
					downloadLfsResource(lfs, db, res);
				}
				this.in = Files.newInputStream(mediaFile);
			}
		} finally {
			in.close(); // make sure the swapped stream is closed properly.
		}
	}

	/**
	 * Download content which is hosted on a LFS server
	 *
	 * @param lfs
	 *            local {@link Lfs} storage.
	 * @param db
	 *            the repository to work with
	 * @param res
	 *            the objects to download
	 * @return the paths of all mediafiles which have been downloaded
	 * @throws IOException
	 * @since 4.11
	 */
	public static Collection<Path> downloadLfsResource(Lfs lfs, Repository db,
			LfsPointer... res) throws IOException {
		Collection<Path> downloadedPaths = new ArrayList<>();
		Map<String, LfsPointer> oidStr2ptr = new HashMap<>();
		for (LfsPointer p : res) {
			oidStr2ptr.put(p.getOid().name(), p);
		}
		HttpConnection lfsServerConn = LfsConnectionFactory.getLfsConnection(db,
				HttpSupport.METHOD_POST, Protocol.OPERATION_DOWNLOAD);
		Gson gson = Protocol.gson();
		lfsServerConn.getOutputStream()
				.write(gson
						.toJson(LfsConnectionFactory
								.toRequest(Protocol.OPERATION_DOWNLOAD, res))
						.getBytes(UTF_8));
		int responseCode = lfsServerConn.getResponseCode();
		if (responseCode != HttpConnection.HTTP_OK) {
			throw new IOException(
					MessageFormat.format(LfsText.get().serverFailure,
							lfsServerConn.getURL(),
							Integer.valueOf(responseCode)));
		}
		try (JsonReader reader = new JsonReader(
				new InputStreamReader(lfsServerConn.getInputStream(),
						UTF_8))) {
			Protocol.Response resp = gson.fromJson(reader,
					Protocol.Response.class);
			for (Protocol.ObjectInfo o : resp.objects) {
				if (o.error != null) {
					throw new IOException(
							MessageFormat.format(LfsText.get().protocolError,
									Integer.valueOf(o.error.code),
									o.error.message));
				}
				if (o.actions == null) {
					continue;
				}
				LfsPointer ptr = oidStr2ptr.get(o.oid);
				if (ptr == null) {
					// received an object we didn't request
					continue;
				}
				if (ptr.getSize() != o.size) {
					throw new IOException(MessageFormat.format(
							LfsText.get().inconsistentContentLength,
							lfsServerConn.getURL(), Long.valueOf(ptr.getSize()),
							Long.valueOf(o.size)));
				}
				Protocol.Action downloadAction = o.actions
						.get(Protocol.OPERATION_DOWNLOAD);
				if (downloadAction == null || downloadAction.href == null) {
					continue;
				}

				HttpConnection contentServerConn = LfsConnectionFactory
						.getLfsContentConnection(db, downloadAction,
								HttpSupport.METHOD_GET);

				responseCode = contentServerConn.getResponseCode();
				if (responseCode != HttpConnection.HTTP_OK) {
					throw new IOException(
							MessageFormat.format(LfsText.get().serverFailure,
									contentServerConn.getURL(),
									Integer.valueOf(responseCode)));
				}
				Path path = lfs.getMediaFile(ptr.getOid());
				Path parent = path.getParent();
				if (parent != null) {
					parent.toFile().mkdirs();
				}
				try (InputStream contentIn = contentServerConn
						.getInputStream()) {
					long bytesCopied = Files.copy(contentIn, path);
					if (bytesCopied != o.size) {
						throw new IOException(MessageFormat.format(
								LfsText.get().wrongAmoutOfDataReceived,
								contentServerConn.getURL(),
								Long.valueOf(bytesCopied),
								Long.valueOf(o.size)));
					}
					downloadedPaths.add(path);
				}
			}
		}
		return downloadedPaths;
	}

	/** {@inheritDoc} */
	@Override
	public int run() throws IOException {
		try {
			int totalRead = 0;
			int length = 0;
			if (in != null) {
				byte[] buf = new byte[8192];
				while ((length = in.read(buf)) != -1) {
					out.write(buf, 0, length);
					totalRead += length;

					// when threshold reached, loop back to the caller.
					// otherwise we could only support files up to 2GB (int
					// return type) properly. we will be called again as long as
					// we don't return -1 here.
					if (totalRead >= MAX_COPY_BYTES) {
						// leave streams open - we need them in the next call.
						return totalRead;
					}
				}
			}

			if (totalRead == 0 && length == -1) {
				// we're totally done :) cleanup all streams
				in.close();
				out.close();
				return length;
			}

			return totalRead;
		} catch (IOException e) {
			in.close(); // clean up - we swapped this stream.
			out.close();
			throw e;
		}
	}

}