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

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;

import org.eclipse.jgit.attributes.FilterCommand;
import org.eclipse.jgit.attributes.FilterCommandFactory;
import org.eclipse.jgit.attributes.FilterCommandRegistry;
import org.eclipse.jgit.lfs.errors.CorruptMediaFile;
import org.eclipse.jgit.lfs.internal.AtomicObjectOutputStream;
import org.eclipse.jgit.lfs.lib.AnyLongObjectId;
import org.eclipse.jgit.lfs.lib.Constants;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.util.FileUtils;

/**
 * Built-in LFS clean filter
 *
 * When new content is about to be added to the git repository and this filter
 * is configured for that content, then this filter will replace the original
 * content with content of a so-called LFS pointer file. The pointer file
 * content will then be added to the git repository. Additionally this filter
 * writes the original content in a so-called 'media file' to '.git/lfs/objects/
 * &lt;first-two-characters-of-contentid&gt;/&lt;rest-of-contentid&gt;'
 *
 * @see <a href="https://github.com/github/git-lfs/blob/master/docs/spec.md">Git
 *      LFS Specification</a>
 * @since 4.6
 */
public class CleanFilter extends FilterCommand {
	/**
	 * The factory is responsible for creating instances of
	 * {@link org.eclipse.jgit.lfs.CleanFilter}
	 */
	public final static FilterCommandFactory FACTORY = CleanFilter::new;

	/**
	 * Registers this filter by calling
	 * {@link FilterCommandRegistry#register(String, FilterCommandFactory)}
	 */
	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_CLEAN,
						FACTORY);
	}

	// Used to compute the hash for the original content
	private AtomicObjectOutputStream aOut;

	private Lfs lfsUtil;

	// the size of the original content
	private long size;

	// a temporary file into which the original content is written. When no
	// errors occur this file will be renamed to the mediafile
	private Path tmpFile;

	/**
	 * Constructor for CleanFilter.
	 *
	 * @param db
	 *            the repository
	 * @param in
	 *            an {@link java.io.InputStream} providing the original content
	 * @param out
	 *            the {@link java.io.OutputStream} into which the content of the
	 *            pointer file should be written. That's the content which will
	 *            be added to the git repository
	 * @throws java.io.IOException
	 *             when the creation of the temporary file fails or when no
	 *             {@link java.io.OutputStream} for this file can be created
	 */
	public CleanFilter(Repository db, InputStream in, OutputStream out)
			throws IOException {
		super(in, out);
		lfsUtil = new Lfs(db);
		Files.createDirectories(lfsUtil.getLfsTmpDir());
		tmpFile = lfsUtil.createTmpFile();
		this.aOut = new AtomicObjectOutputStream(tmpFile.toAbsolutePath());
	}

	/** {@inheritDoc} */
	@Override
	public int run() throws IOException {
		try {
			byte[] buf = new byte[8192];
			int length = in.read(buf);
			if (length != -1) {
				aOut.write(buf, 0, length);
				size += length;
				return length;
			}
			aOut.close();
			AnyLongObjectId loid = aOut.getId();
			aOut = null;
			Path mediaFile = lfsUtil.getMediaFile(loid);
			if (Files.isRegularFile(mediaFile)) {
				long fsSize = Files.size(mediaFile);
				if (fsSize != size) {
					throw new CorruptMediaFile(mediaFile, size, fsSize);
				}
				FileUtils.delete(tmpFile.toFile());
			} else {
				Path parent = mediaFile.getParent();
				if (parent != null) {
					FileUtils.mkdirs(parent.toFile(), true);
				}
				FileUtils.rename(tmpFile.toFile(), mediaFile.toFile(),
						StandardCopyOption.ATOMIC_MOVE);
			}
			LfsPointer lfsPointer = new LfsPointer(loid, size);
			lfsPointer.encode(out);
			in.close();
			out.close();
			return -1;
		} catch (IOException e) {
			if (aOut != null) {
				aOut.abort();
			}
			in.close();
			out.close();
			throw e;
		}
	}
}