/*
    * Copyright (C) 2018, Markus Duft <markus.duft@ssi-schaefer.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,
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   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package org.eclipse.jgit.util;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintStream;
  import java.text.MessageFormat;
  import java.util.concurrent.Callable;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.attributes.Attribute;
  import org.eclipse.jgit.attributes.Attributes;
  import org.eclipse.jgit.hooks.PrePushHook;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.ObjectLoader;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.treewalk.FileTreeIterator;
  import org.eclipse.jgit.treewalk.TreeWalk;
  import org.eclipse.jgit.treewalk.filter.PathFilter;
  
  /**
   * Represents an optionally present LFS support implementation
   *
   * @since 4.11
   */
  public class LfsFactory {
  
  	private static LfsFactory instance = new LfsFactory();
  
  	/**
  	 * Constructor
  	 */
  	protected LfsFactory() {
  	}
  
  	/**
  	 * @return the current LFS implementation
  	 */
  	public static LfsFactory getInstance() {
  		return instance;
  	}
  
  	/**
  	 * @param instance
  	 *            register a {@link LfsFactory} instance as the
  	 *            {@link LfsFactory} implementation to use.
  	 */
  	public static void setInstance(LfsFactory instance) {
  		LfsFactory.instance = instance;
  	}
  
  	/**
  	 * @return whether LFS support is available
  	 */
  	public boolean isAvailable() {
  		return false;
  	}
 
 	/**
 	 * Apply clean filtering to the given stream, writing the file content to
 	 * the LFS storage if required and returning a stream to the LFS pointer
 	 * instead.
 	 *
 	 * @param db
 	 *            the repository
 	 * @param input
 	 *            the original input
 	 * @param length
 	 *            the expected input stream length
 	 * @param attribute
 	 *            the attribute used to check for LFS enablement (i.e. "merge",
 	 *            "diff", "filter" from .gitattributes).
 	 * @return a stream to the content that should be written to the object
 	 *         store along with the expected length of the stream. the original
 	 *         stream is not applicable.
 	 * @throws IOException
 	 *             in case of an error
 	 */
 	public LfsInputStream applyCleanFilter(Repository db,
 			InputStream input, long length, Attribute attribute)
 			throws IOException {
 		return new LfsInputStream(input, length);
 	}
 
 	/**
 	 * Apply smudge filtering to a given loader, potentially redirecting it to a
 	 * LFS blob which is downloaded on demand.
 	 *
 	 * @param db
 	 *            the repository
 	 * @param loader
 	 *            the loader for the blob
 	 * @param attribute
 	 *            the attribute used to check for LFS enablement (i.e. "merge",
 	 *            "diff", "filter" from .gitattributes).
 	 * @return a loader for the actual data of a blob, or the original loader in
 	 *         case LFS is not applicable.
 	 * @throws IOException
 	 */
 	public ObjectLoader applySmudgeFilter(Repository db,
 			ObjectLoader loader, Attribute attribute) throws IOException {
 		return loader;
 	}
 
 	/**
 	 * Retrieve a pre-push hook to be applied.
 	 *
 	 * @param repo
 	 *            the {@link Repository} the hook is applied to.
 	 * @param outputStream
 	 * @return a {@link PrePushHook} implementation or <code>null</code>
 	 */
 	public @Nullable PrePushHook getPrePushHook(Repository repo,
 			PrintStream outputStream) {
 		return null;
 	}
 
 	/**
 	 * Retrieve an {@link LfsInstallCommand} which can be used to enable LFS
 	 * support (if available) either per repository or for the user.
 	 *
 	 * @return a command to install LFS support.
 	 */
 	public @Nullable LfsInstallCommand getInstallCommand() {
 		return null;
 	}
 
 	/**
 	 * @param db
 	 *            the repository to check
 	 * @return whether LFS is enabled for the given repository locally or
 	 *         globally.
 	 */
 	public boolean isEnabled(Repository db) {
 		return false;
 	}
 
 	/**
 	 * @param db
 	 *            the repository
 	 * @param path
 	 *            the path to find attributes for
 	 * @return the {@link Attributes} for the given path.
 	 * @throws IOException
 	 *             in case of an error
 	 */
 	public static Attributes getAttributesForPath(Repository db, String path)
 			throws IOException {
 		try (TreeWalk walk = new TreeWalk(db)) {
 			walk.addTree(new FileTreeIterator(db));
 			PathFilter f = PathFilter.create(path);
 			walk.setFilter(f);
 			walk.setRecursive(false);
 			Attributes attr = null;
 			while (walk.next()) {
 				if (f.isDone(walk)) {
 					attr = walk.getAttributes();
 					break;
 				} else if (walk.isSubtree()) {
 					walk.enterSubtree();
 				}
 			}
 			if (attr == null) {
 				throw new IOException(MessageFormat
 						.format(JGitText.get().noPathAttributesFound, path));
 			}
 
 			return attr;
 		}
 	}
 
 	/**
 	 * Get attributes for given path and commit
 	 *
 	 * @param db
 	 *            the repository
 	 * @param path
 	 *            the path to find attributes for
 	 * @param commit
 	 *            the commit to inspect.
 	 * @return the {@link Attributes} for the given path.
 	 * @throws IOException
 	 *             in case of an error
 	 */
 	public static Attributes getAttributesForPath(Repository db, String path,
 			RevCommit commit) throws IOException {
 		if (commit == null) {
 			return getAttributesForPath(db, path);
 		}
 
 		try (TreeWalk walk = TreeWalk.forPath(db, path, commit.getTree())) {
 			Attributes attr = walk == null ? null : walk.getAttributes();
 			if (attr == null) {
 				throw new IOException(MessageFormat
 						.format(JGitText.get().noPathAttributesFound, path));
 			}
 
 			return attr;
 		}
 	}
 
 	/**
 	 * Encapsulate a potentially exchanged {@link InputStream} along with the
 	 * expected stream content length.
 	 */
 	public static final class LfsInputStream extends InputStream {
 		/**
 		 * The actual stream.
 		 */
 		private InputStream stream;
 
 		/**
 		 * The expected stream content length.
 		 */
 		private long length;
 
 		/**
 		 * Create a new wrapper around a certain stream
 		 *
 		 * @param stream
 		 *            the stream to wrap. the stream will be closed on
 		 *            {@link #close()}.
 		 * @param length
 		 *            the expected length of the stream
 		 */
 		public LfsInputStream(InputStream stream, long length) {
 			this.stream = stream;
 			this.length = length;
 		}
 
 		/**
 		 * Create a new wrapper around a temporary buffer.
 		 *
 		 * @param buffer
 		 *            the buffer to initialize stream and length from. The
 		 *            buffer will be destroyed on {@link #close()}
 		 * @throws IOException
 		 *             in case of an error opening the stream to the buffer.
 		 */
 		public LfsInputStream(TemporaryBuffer buffer) throws IOException {
 			this.stream = buffer.openInputStreamWithAutoDestroy();
 			this.length = buffer.length();
 		}
 
 		@Override
 		public void close() throws IOException {
 			stream.close();
 		}
 
 		@Override
 		public int read() throws IOException {
 			return stream.read();
 		}
 
 		/**
 		 * @return the length of the stream
 		 */
 		public long getLength() {
 			return length;
 		}
 	}
 
 	/**
 	 * A command to enable LFS. Optionally set a {@link Repository} to enable
 	 * locally on the repository only.
 	 */
 	public interface LfsInstallCommand extends Callable<Void> {
 		/**
 		 * @param repo
 		 *            the repository to enable support for.
 		 * @return The {@link LfsInstallCommand} for chaining.
 		 */
 		public LfsInstallCommand setRepository(Repository repo);
 	}
 
 }