/*
 * Copyright (C) 2009, Constantine Plotnikov <constantine.plotnikov@gmail.com>
 * Copyright (C) 2007, Dave Watson <dwatson@mimvista.com>
 * Copyright (C) 2009, Google Inc.
 * Copyright (C) 2009, JetBrains s.r.o.
 * Copyright (C) 2008-2009, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * Copyright (C) 2008, Thad Hughes <thadh@thad.corp.google.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.storage.file;

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

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.text.MessageFormat;

import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.errors.LockFailedException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.internal.storage.file.FileSnapshot;
import org.eclipse.jgit.internal.storage.file.LockFile;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.StoredConfig;
import org.eclipse.jgit.util.FS;
import org.eclipse.jgit.util.FileUtils;
import org.eclipse.jgit.util.IO;
import org.eclipse.jgit.util.RawParseUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

The configuration file that is stored in the file of the file system.
/**
 * The configuration file that is stored in the file of the file system.
 */
public class FileBasedConfig extends StoredConfig {
	private static final Logger LOG = LoggerFactory
			.getLogger(FileBasedConfig.class);

	private final File configFile;

	private final FS fs;

	private boolean utf8Bom;

	private volatile FileSnapshot snapshot;

	private volatile ObjectId hash;

	
Create a configuration with no default fallback.
Params:
cfgLocation – 
           the location of the configuration file on the file system
fs – 
           the file system abstraction which will be necessary to perform
           certain file system operations./**
	 * Create a configuration with no default fallback.
	 *
	 * @param cfgLocation
	 *            the location of the configuration file on the file system
	 * @param fs
	 *            the file system abstraction which will be necessary to perform
	 *            certain file system operations.
	 */
	public FileBasedConfig(File cfgLocation, FS fs) {
		this(null, cfgLocation, fs);
	}

	
The constructor
Params:
base – 
           the base configuration file
cfgLocation – 
           the location of the configuration file on the file system
fs – 
           the file system abstraction which will be necessary to perform
           certain file system operations./**
	 * The constructor
	 *
	 * @param base
	 *            the base configuration file
	 * @param cfgLocation
	 *            the location of the configuration file on the file system
	 * @param fs
	 *            the file system abstraction which will be necessary to perform
	 *            certain file system operations.
	 */
	public FileBasedConfig(Config base, File cfgLocation, FS fs) {
		super(base);
		configFile = cfgLocation;
		this.fs = fs;
		this.snapshot = FileSnapshot.DIRTY;
		this.hash = ObjectId.zeroId();
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	protected boolean notifyUponTransientChanges() {
		// we will notify listeners upon save()
		return false;
	}

	
Get location of the configuration file on disk
Returns:
location of the configuration file on disk/**
	 * Get location of the configuration file on disk
	 *
	 * @return location of the configuration file on disk
	 */
	public final File getFile() {
		return configFile;
	}

	
{@inheritDoc}

Load the configuration as a Git text style configuration file.

If the file does not exist, this configuration is cleared, and thus
behaves the same as though the file exists, but is empty.
/**
	 * {@inheritDoc}
	 * <p>
	 * Load the configuration as a Git text style configuration file.
	 * <p>
	 * If the file does not exist, this configuration is cleared, and thus
	 * behaves the same as though the file exists, but is empty.
	 */
	@Override
	public void load() throws IOException, ConfigInvalidException {
		final int maxRetries = 5;
		int retryDelayMillis = 20;
		int retries = 0;
		while (true) {
			final FileSnapshot oldSnapshot = snapshot;
			final FileSnapshot newSnapshot;
			// don't use config in this snapshot to avoid endless recursion
			newSnapshot = FileSnapshot.saveNoConfig(getFile());
			try {
				final byte[] in = IO.readFully(getFile());
				final ObjectId newHash = hash(in);
				if (hash.equals(newHash)) {
					if (oldSnapshot.equals(newSnapshot)) {
						oldSnapshot.setClean(newSnapshot);
					} else {
						snapshot = newSnapshot;
					}
				} else {
					final String decoded;
					if (isUtf8(in)) {
						decoded = RawParseUtils.decode(UTF_8,
								in, 3, in.length);
						utf8Bom = true;
					} else {
						decoded = RawParseUtils.decode(in);
					}
					fromText(decoded);
					snapshot = newSnapshot;
					hash = newHash;
				}
				return;
			} catch (FileNotFoundException noFile) {
				// might be locked by another process (see exception Javadoc)
				if (retries < maxRetries && configFile.exists()) {
					if (LOG.isDebugEnabled()) {
						LOG.debug(MessageFormat.format(
								JGitText.get().configHandleMayBeLocked,
								Integer.valueOf(retries)), noFile);
					}
					try {
						Thread.sleep(retryDelayMillis);
					} catch (InterruptedException e) {
						Thread.currentThread().interrupt();
					}
					retries++;
					retryDelayMillis *= 2; // max wait 1260 ms
					continue;
				}
				if (configFile.exists()) {
					throw noFile;
				}
				clear();
				snapshot = newSnapshot;
				return;
			} catch (IOException e) {
				if (FileUtils.isStaleFileHandle(e)
						&& retries < maxRetries) {
					if (LOG.isDebugEnabled()) {
						LOG.debug(MessageFormat.format(
								JGitText.get().configHandleIsStale,
								Integer.valueOf(retries)), e);
					}
					retries++;
					continue;
				}
				throw new IOException(MessageFormat
						.format(JGitText.get().cannotReadFile, getFile()), e);
			} catch (ConfigInvalidException e) {
				throw new ConfigInvalidException(MessageFormat
						.format(JGitText.get().cannotReadFile, getFile()), e);
			}
		}
	}

	
{@inheritDoc}

Save the configuration as a Git text style configuration file.

Warning: Although this method uses the traditional Git file
locking approach to protect against concurrent writes of the
configuration file, it does not ensure that the file has not been
modified since the last read, which means updates performed by other
objects accessing the same backing file may be lost.
/**
	 * {@inheritDoc}
	 * <p>
	 * Save the configuration as a Git text style configuration file.
	 * <p>
	 * <b>Warning:</b> Although this method uses the traditional Git file
	 * locking approach to protect against concurrent writes of the
	 * configuration file, it does not ensure that the file has not been
	 * modified since the last read, which means updates performed by other
	 * objects accessing the same backing file may be lost.
	 */
	@Override
	public void save() throws IOException {
		final byte[] out;
		final String text = toText();
		if (utf8Bom) {
			final ByteArrayOutputStream bos = new ByteArrayOutputStream();
			bos.write(0xEF);
			bos.write(0xBB);
			bos.write(0xBF);
			bos.write(text.getBytes(UTF_8));
			out = bos.toByteArray();
		} else {
			out = Constants.encode(text);
		}

		final LockFile lf = new LockFile(getFile());
		if (!lf.lock())
			throw new LockFailedException(getFile());
		try {
			lf.setNeedSnapshot(true);
			lf.write(out);
			if (!lf.commit())
				throw new IOException(MessageFormat.format(JGitText.get().cannotCommitWriteTo, getFile()));
		} finally {
			lf.unlock();
		}
		snapshot = lf.getCommitSnapshot();
		hash = hash(out);
		// notify the listeners
		fireConfigChangedEvent();
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public void clear() {
		hash = hash(new byte[0]);
		super.clear();
	}

	private static ObjectId hash(byte[] rawText) {
		return ObjectId.fromRaw(Constants.newMessageDigest().digest(rawText));
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@SuppressWarnings("nls")
	@Override
	public String toString() {
		return getClass().getSimpleName() + "[" + getFile().getPath() + "]";
	}

	
Whether the currently loaded configuration file is outdated
Returns:
returns true if the currently loaded configuration file is older
        than the file on disk/**
	 * Whether the currently loaded configuration file is outdated
	 *
	 * @return returns true if the currently loaded configuration file is older
	 *         than the file on disk
	 */
	public boolean isOutdated() {
		return snapshot.isModified(getFile());
	}

	
{@inheritDoc}
Since:
4.10/**
	 * {@inheritDoc}
	 *
	 * @since 4.10
	 */
	@Override
	protected byte[] readIncludedConfig(String relPath)
			throws ConfigInvalidException {
		final File file;
		if (relPath.startsWith("~/")) { //$NON-NLS-1$
			file = fs.resolve(fs.userHome(), relPath.substring(2));
		} else {
			file = fs.resolve(configFile.getParentFile(), relPath);
		}

		if (!file.exists()) {
			return null;
		}

		try {
			return IO.readFully(file);
		} catch (IOException ioe) {
			throw new ConfigInvalidException(MessageFormat
					.format(JGitText.get().cannotReadFile, relPath), ioe);
		}
	}
}