/*
 * Copyright (C) 2007, Dave Watson <dwatson@mimvista.com>
 * Copyright (C) 2008-2010, Google Inc.
 * Copyright (C) 2006-2010, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2006-2008, 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.internal.storage.file;

import static org.eclipse.jgit.lib.RefDatabase.ALL;

import java.io.File;
import java.io.IOException;
import java.text.MessageFormat;
import java.util.HashSet;
import java.util.Set;

import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.events.ConfigChangedEvent;
import org.eclipse.jgit.events.ConfigChangedListener;
import org.eclipse.jgit.events.IndexChangedEvent;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.internal.storage.file.ObjectDirectory.AlternateHandle;
import org.eclipse.jgit.internal.storage.file.ObjectDirectory.AlternateRepository;
import org.eclipse.jgit.lib.BaseRepositoryBuilder;
import org.eclipse.jgit.lib.ConfigConstants;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.CoreConfig.SymLinks;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefDatabase;
import org.eclipse.jgit.lib.RefUpdate;
import org.eclipse.jgit.lib.ReflogReader;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.storage.file.FileBasedConfig;
import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
import org.eclipse.jgit.util.FS;
import org.eclipse.jgit.util.FileUtils;
import org.eclipse.jgit.util.StringUtils;
import org.eclipse.jgit.util.SystemReader;

/**
 * Represents a Git repository. A repository holds all objects and refs used for
 * managing source code (could by any type of file, but source code is what
 * SCM's are typically used for).
 *
 * In Git terms all data is stored in GIT_DIR, typically a directory called
 * .git. A work tree is maintained unless the repository is a bare repository.
 * Typically the .git directory is located at the root of the work dir.
 *
 * <ul>
 * <li>GIT_DIR
 * 	<ul>
 * 		<li>objects/ - objects</li>
 * 		<li>refs/ - tags and heads</li>
 * 		<li>config - configuration</li>
 * 		<li>info/ - more configurations</li>
 * 	</ul>
 * </li>
 * </ul>
 * <p>
 * This class is thread-safe.
 * <p>
 * This implementation only handles a subtly undocumented subset of git features.
 *
 */
public class FileRepository extends Repository {
	private final FileBasedConfig systemConfig;

	private final FileBasedConfig userConfig;

	private final FileBasedConfig repoConfig;

	private final RefDatabase refs;

	private final ObjectDirectory objectDatabase;

	private FileSnapshot snapshot;

	/**
	 * Construct a representation of a Git repository.
	 * <p>
	 * The work tree, object directory, alternate object directories and index
	 * file locations are deduced from the given git directory and the default
	 * rules by running {@link FileRepositoryBuilder}. This constructor is the
	 * same as saying:
	 *
	 * <pre>
	 * new FileRepositoryBuilder().setGitDir(gitDir).build()
	 * </pre>
	 *
	 * @param gitDir
	 *            GIT_DIR (the location of the repository metadata).
	 * @throws IOException
	 *             the repository appears to already exist but cannot be
	 *             accessed.
	 * @see FileRepositoryBuilder
	 */
	public FileRepository(final File gitDir) throws IOException {
		this(new FileRepositoryBuilder().setGitDir(gitDir).setup());
	}

	/**
	 * A convenience API for {@link #FileRepository(File)}.
	 *
	 * @param gitDir
	 *            GIT_DIR (the location of the repository metadata).
	 * @throws IOException
	 *             the repository appears to already exist but cannot be
	 *             accessed.
	 * @see FileRepositoryBuilder
	 */
	public FileRepository(final String gitDir) throws IOException {
		this(new File(gitDir));
	}

	/**
	 * Create a repository using the local file system.
	 *
	 * @param options
	 *            description of the repository's important paths.
	 * @throws IOException
	 *             the user configuration file or repository configuration file
	 *             cannot be accessed.
	 */
	public FileRepository(final BaseRepositoryBuilder options) throws IOException {
		super(options);

		if (StringUtils.isEmptyOrNull(SystemReader.getInstance().getenv(
				Constants.GIT_CONFIG_NOSYSTEM_KEY)))
			systemConfig = SystemReader.getInstance().openSystemConfig(null,
					getFS());
		else
			systemConfig = new FileBasedConfig(null, FS.DETECTED) {
				public void load() {
					// empty, do not load
				}

				public boolean isOutdated() {
					// regular class would bomb here
					return false;
				}
			};
		userConfig = SystemReader.getInstance().openUserConfig(systemConfig,
				getFS());
		repoConfig = new FileBasedConfig(userConfig, getFS().resolve(
				getDirectory(), Constants.CONFIG),
				getFS());

		loadSystemConfig();
		loadUserConfig();
		loadRepoConfig();

		repoConfig.addChangeListener(new ConfigChangedListener() {
			public void onConfigChanged(ConfigChangedEvent event) {
				fireEvent(event);
			}
		});

		refs = new RefDirectory(this);
		objectDatabase = new ObjectDirectory(repoConfig, //
				options.getObjectDirectory(), //
				options.getAlternateObjectDirectories(), //
				getFS(), //
				new File(getDirectory(), Constants.SHALLOW));

		if (objectDatabase.exists()) {
			final long repositoryFormatVersion = getConfig().getLong(
					ConfigConstants.CONFIG_CORE_SECTION, null,
					ConfigConstants.CONFIG_KEY_REPO_FORMAT_VERSION, 0);
			if (repositoryFormatVersion > 0)
				throw new IOException(MessageFormat.format(
						JGitText.get().unknownRepositoryFormat2,
						Long.valueOf(repositoryFormatVersion)));
		}

		if (!isBare())
			snapshot = FileSnapshot.save(getIndexFile());
	}

	private void loadSystemConfig() throws IOException {
		try {
			systemConfig.load();
		} catch (ConfigInvalidException e1) {
			IOException e2 = new IOException(MessageFormat.format(JGitText
					.get().systemConfigFileInvalid, systemConfig.getFile()
					.getAbsolutePath(), e1));
			e2.initCause(e1);
			throw e2;
		}
	}

	private void loadUserConfig() throws IOException {
		try {
			userConfig.load();
		} catch (ConfigInvalidException e1) {
			IOException e2 = new IOException(MessageFormat.format(JGitText
					.get().userConfigFileInvalid, userConfig.getFile()
					.getAbsolutePath(), e1));
			e2.initCause(e1);
			throw e2;
		}
	}

	private void loadRepoConfig() throws IOException {
		try {
			repoConfig.load();
		} catch (ConfigInvalidException e1) {
			IOException e2 = new IOException(JGitText.get().unknownRepositoryFormat);
			e2.initCause(e1);
			throw e2;
		}
	}

	/**
	 * Create a new Git repository initializing the necessary files and
	 * directories.
	 *
	 * @param bare
	 *            if true, a bare repository is created.
	 *
	 * @throws IOException
	 *             in case of IO problem
	 */
	public void create(boolean bare) throws IOException {
		final FileBasedConfig cfg = getConfig();
		if (cfg.getFile().exists()) {
			throw new IllegalStateException(MessageFormat.format(
					JGitText.get().repositoryAlreadyExists, getDirectory()));
		}
		FileUtils.mkdirs(getDirectory(), true);
		refs.create();
		objectDatabase.create();

		FileUtils.mkdir(new File(getDirectory(), "branches")); //$NON-NLS-1$
		FileUtils.mkdir(new File(getDirectory(), "hooks")); //$NON-NLS-1$

		RefUpdate head = updateRef(Constants.HEAD);
		head.disableRefLog();
		head.link(Constants.R_HEADS + Constants.MASTER);

		final boolean fileMode;
		if (getFS().supportsExecute()) {
			File tmp = File.createTempFile("try", "execute", getDirectory()); //$NON-NLS-1$ //$NON-NLS-2$

			getFS().setExecute(tmp, true);
			final boolean on = getFS().canExecute(tmp);

			getFS().setExecute(tmp, false);
			final boolean off = getFS().canExecute(tmp);
			FileUtils.delete(tmp);

			fileMode = on && !off;
		} else {
			fileMode = false;
		}

		SymLinks symLinks = SymLinks.FALSE;
		if (getFS().supportsSymlinks()) {
			File tmp = new File(getDirectory(), "tmplink"); //$NON-NLS-1$
			try {
				getFS().createSymLink(tmp, "target"); //$NON-NLS-1$
				symLinks = null;
				FileUtils.delete(tmp);
			} catch (IOException e) {
				// Normally a java.nio.file.FileSystemException
			}
		}
		if (symLinks != null)
			cfg.setString(ConfigConstants.CONFIG_CORE_SECTION, null,
					ConfigConstants.CONFIG_KEY_SYMLINKS, symLinks.name()
							.toLowerCase());
		cfg.setInt(ConfigConstants.CONFIG_CORE_SECTION, null,
				ConfigConstants.CONFIG_KEY_REPO_FORMAT_VERSION, 0);
		cfg.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
				ConfigConstants.CONFIG_KEY_FILEMODE, fileMode);
		if (bare)
			cfg.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
					ConfigConstants.CONFIG_KEY_BARE, true);
		cfg.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
				ConfigConstants.CONFIG_KEY_LOGALLREFUPDATES, !bare);
		if (SystemReader.getInstance().isMacOS())
			// Java has no other way
			cfg.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
					ConfigConstants.CONFIG_KEY_PRECOMPOSEUNICODE, true);
		cfg.save();
	}

	/**
	 * @return the directory containing the objects owned by this repository.
	 */
	public File getObjectsDirectory() {
		return objectDatabase.getDirectory();
	}

	/**
	 * @return the object database which stores this repository's data.
	 */
	public ObjectDirectory getObjectDatabase() {
		return objectDatabase;
	}

	/** @return the reference database which stores the reference namespace. */
	public RefDatabase getRefDatabase() {
		return refs;
	}

	/**
	 * @return the configuration of this repository
	 */
	public FileBasedConfig getConfig() {
		if (systemConfig.isOutdated()) {
			try {
				loadSystemConfig();
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		if (userConfig.isOutdated()) {
			try {
				loadUserConfig();
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		if (repoConfig.isOutdated()) {
				try {
					loadRepoConfig();
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
		}
		return repoConfig;
	}

	/**
	 * Objects known to exist but not expressed by {@link #getAllRefs()}.
	 * <p>
	 * When a repository borrows objects from another repository, it can
	 * advertise that it safely has that other repository's references, without
	 * exposing any other details about the other repository.  This may help
	 * a client trying to push changes avoid pushing more than it needs to.
	 *
	 * @return unmodifiable collection of other known objects.
	 */
	public Set<ObjectId> getAdditionalHaves() {
		HashSet<ObjectId> r = new HashSet<ObjectId>();
		for (AlternateHandle d : objectDatabase.myAlternates()) {
			if (d instanceof AlternateRepository) {
				Repository repo;

				repo = ((AlternateRepository) d).repository;
				for (Ref ref : repo.getAllRefs().values()) {
					if (ref.getObjectId() != null)
						r.add(ref.getObjectId());
					if (ref.getPeeledObjectId() != null)
						r.add(ref.getPeeledObjectId());
				}
				r.addAll(repo.getAdditionalHaves());
			}
		}
		return r;
	}

	/**
	 * Add a single existing pack to the list of available pack files.
	 *
	 * @param pack
	 *            path of the pack file to open.
	 * @throws IOException
	 *             index file could not be opened, read, or is not recognized as
	 *             a Git pack file index.
	 */
	public void openPack(final File pack) throws IOException {
		objectDatabase.openPack(pack);
	}

	@Override
	public void scanForRepoChanges() throws IOException {
		getRefDatabase().getRefs(ALL); // This will look for changes to refs
		detectIndexChanges();
	}

	/**
	 * Detect index changes.
	 */
	private void detectIndexChanges() {
		if (isBare())
			return;

		File indexFile = getIndexFile();
		if (snapshot == null)
			snapshot = FileSnapshot.save(indexFile);
		else if (snapshot.isModified(indexFile))
			notifyIndexChanged();
	}

	@Override
	public void notifyIndexChanged() {
		snapshot = FileSnapshot.save(getIndexFile());
		fireEvent(new IndexChangedEvent());
	}

	/**
	 * @param refName
	 * @return a {@link ReflogReader} for the supplied refname, or null if the
	 *         named ref does not exist.
	 * @throws IOException the ref could not be accessed.
	 */
	public ReflogReader getReflogReader(String refName) throws IOException {
		Ref ref = getRef(refName);
		if (ref != null)
			return new ReflogReaderImpl(this, ref.getName());
		return null;
	}
}
