/*
    * 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.HideDotFiles;
  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);
 		HideDotFiles hideDotFiles = getConfig().getEnum(
 				ConfigConstants.CONFIG_CORE_SECTION, null,
 				ConfigConstants.CONFIG_KEY_HIDEDOTFILES,
 				HideDotFiles.DOTGITONLY);
 		if (hideDotFiles != HideDotFiles.FALSE && !isBare()
 				&& getDirectory().getName().startsWith(".")) //$NON-NLS-1$
 			getFS().setHidden(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);
 		if (!bare) {
 			File workTree = getWorkTree();
 			if (!getDirectory().getParentFile().equals(workTree)) {
 				cfg.setString(ConfigConstants.CONFIG_CORE_SECTION, null,
 						ConfigConstants.CONFIG_KEY_WORKTREE, getWorkTree()
 								.getAbsolutePath());
 				LockFile dotGitLockFile = new LockFile(new File(workTree,
 						Constants.DOT_GIT), getFS());
 				try {
 					if (dotGitLockFile.lock()) {
 						dotGitLockFile.write(Constants.encode(Constants.GITDIR
 								+ getDirectory().getAbsolutePath()));
 						dotGitLockFile.commit();
 					}
 				} finally {
 					dotGitLockFile.unlock();
 				}
 			}
 		}
 		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;
 	}
 }