/*
    * Copyright (C) 2008-2009, Google Inc.
    * Copyright (C) 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,
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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.dircache;
  
  import java.io.IOException;
  import java.text.MessageFormat;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.List;
  
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.Constants;
  
  /**
   * Updates a {@link DirCache} by supplying discrete edit commands.
   * <p>
   * An editor updates a DirCache by taking a list of {@link PathEdit} commands
   * and executing them against the entries of the destination cache to produce a
   * new cache. This edit style allows applications to insert a few commands and
   * then have the editor compute the proper entry indexes necessary to perform an
   * efficient in-order update of the index records. This can be easier to use
   * than {@link DirCacheBuilder}.
   * <p>
   *
   * @see DirCacheBuilder
   */
  public class DirCacheEditor extends BaseDirCacheEditor {
  	private static final Comparator<PathEdit> EDIT_CMP = new Comparator<PathEdit>() {
  		public int compare(final PathEdit o1, final PathEdit o2) {
  			final byte[] a = o1.path;
  			final byte[] b = o2.path;
  			return DirCache.cmp(a, a.length, b, b.length);
  		}
  	};
  
  	private final List<PathEdit> edits;
  
  	/**
  	 * Construct a new editor.
  	 *
  	 * @param dc
  	 *            the cache this editor will eventually update.
  	 * @param ecnt
  	 *            estimated number of entries the editor will have upon
  	 *            completion. This sizes the initial entry table.
  	 */
  	protected DirCacheEditor(final DirCache dc, final int ecnt) {
  		super(dc, ecnt);
  		edits = new ArrayList<PathEdit>();
  	}
  
  	/**
  	 * Append one edit command to the list of commands to be applied.
  	 * <p>
  	 * Edit commands may be added in any order chosen by the application. They
  	 * are automatically rearranged by the builder to provide the most efficient
 	 * update possible.
 	 *
 	 * @param edit
 	 *            another edit command.
 	 */
 	public void add(final PathEdit edit) {
 		edits.add(edit);
 	}
 
 	@Override
 	public boolean commit() throws IOException {
 		if (edits.isEmpty()) {
 			// No changes? Don't rewrite the index.
 			//
 			cache.unlock();
 			return true;
 		}
 		return super.commit();
 	}
 
 	public void finish() {
 		if (!edits.isEmpty()) {
 			applyEdits();
 			replace();
 		}
 	}
 
 	private void applyEdits() {
 		Collections.sort(edits, EDIT_CMP);
 
 		final int maxIdx = cache.getEntryCount();
 		int lastIdx = 0;
 		for (final PathEdit e : edits) {
 			int eIdx = cache.findEntry(e.path, e.path.length);
 			final boolean missing = eIdx < 0;
 			if (eIdx < 0)
 				eIdx = -(eIdx + 1);
 			final int cnt = Math.min(eIdx, maxIdx) - lastIdx;
 			if (cnt > 0)
 				fastKeep(lastIdx, cnt);
 			lastIdx = missing ? eIdx : cache.nextEntry(eIdx);
 
 			if (e instanceof DeletePath)
 				continue;
 			if (e instanceof DeleteTree) {
 				lastIdx = cache.nextEntry(e.path, e.path.length, eIdx);
 				continue;
 			}
 
 			if (missing) {
 				final DirCacheEntry ent = new DirCacheEntry(e.path);
 				e.apply(ent);
 				if (ent.getRawMode() == 0)
 					throw new IllegalArgumentException(MessageFormat.format(JGitText.get().fileModeNotSetForPath
 							, ent.getPathString()));
 				fastAdd(ent);
 			} else {
 				// Apply to all entries of the current path (different stages)
 				for (int i = eIdx; i < lastIdx; i++) {
 					final DirCacheEntry ent = cache.getEntry(i);
 					e.apply(ent);
 					fastAdd(ent);
 				}
 			}
 		}
 
 		final int cnt = maxIdx - lastIdx;
 		if (cnt > 0)
 			fastKeep(lastIdx, cnt);
 	}
 
 	/**
 	 * Any index record update.
 	 * <p>
 	 * Applications should subclass and provide their own implementation for the
 	 * {@link #apply(DirCacheEntry)} method. The editor will invoke apply once
 	 * for each record in the index which matches the path name. If there are
 	 * multiple records (for example in stages 1, 2 and 3), the edit instance
 	 * will be called multiple times, once for each stage.
 	 */
 	public abstract static class PathEdit {
 		final byte[] path;
 
 		/**
 		 * Create a new update command by path name.
 		 *
 		 * @param entryPath
 		 *            path of the file within the repository.
 		 */
 		public PathEdit(final String entryPath) {
 			path = Constants.encode(entryPath);
 		}
 
 		/**
 		 * Create a new update command for an existing entry instance.
 		 *
 		 * @param ent
 		 *            entry instance to match path of. Only the path of this
 		 *            entry is actually considered during command evaluation.
 		 */
 		public PathEdit(final DirCacheEntry ent) {
 			path = ent.path;
 		}
 
 		/**
 		 * Apply the update to a single cache entry matching the path.
 		 * <p>
 		 * After apply is invoked the entry is added to the output table, and
 		 * will be included in the new index.
 		 *
 		 * @param ent
 		 *            the entry being processed. All fields are zeroed out if
 		 *            the path is a new path in the index.
 		 */
 		public abstract void apply(DirCacheEntry ent);
 	}
 
 	/**
 	 * Deletes a single file entry from the index.
 	 * <p>
 	 * This deletion command removes only a single file at the given location,
 	 * but removes multiple stages (if present) for that path. To remove a
 	 * complete subtree use {@link DeleteTree} instead.
 	 *
 	 * @see DeleteTree
 	 */
 	public static final class DeletePath extends PathEdit {
 		/**
 		 * Create a new deletion command by path name.
 		 *
 		 * @param entryPath
 		 *            path of the file within the repository.
 		 */
 		public DeletePath(final String entryPath) {
 			super(entryPath);
 		}
 
 		/**
 		 * Create a new deletion command for an existing entry instance.
 		 *
 		 * @param ent
 		 *            entry instance to remove. Only the path of this entry is
 		 *            actually considered during command evaluation.
 		 */
 		public DeletePath(final DirCacheEntry ent) {
 			super(ent);
 		}
 
 		public void apply(final DirCacheEntry ent) {
 			throw new UnsupportedOperationException(JGitText.get().noApplyInDelete);
 		}
 	}
 
 	/**
 	 * Recursively deletes all paths under a subtree.
 	 * <p>
 	 * This deletion command is more generic than {@link DeletePath} as it can
 	 * remove all records which appear recursively under the same subtree.
 	 * Multiple stages are removed (if present) for any deleted entry.
 	 * <p>
 	 * This command will not remove a single file entry. To remove a single file
 	 * use {@link DeletePath}.
 	 *
 	 * @see DeletePath
 	 */
 	public static final class DeleteTree extends PathEdit {
 		/**
 		 * Create a new tree deletion command by path name.
 		 *
 		 * @param entryPath
 		 *            path of the subtree within the repository. If the path
 		 *            does not end with "/" a "/" is implicitly added to ensure
 		 *            only the subtree's contents are matched by the command.
 		 *            The special case "" (not "/"!) deletes all entries.
 		 */
 		public DeleteTree(final String entryPath) {
 			super(
 					(entryPath.endsWith("/") || entryPath.length() == 0) ? entryPath //$NON-NLS-1$
 							: entryPath + "/"); //$NON-NLS-1$
 		}
 
 		public void apply(final DirCacheEntry ent) {
 			throw new UnsupportedOperationException(JGitText.get().noApplyInDelete);
 		}
 	}
 }