/*
    * 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 static org.eclipse.jgit.lib.FileMode.TYPE_MASK;
  import static org.eclipse.jgit.lib.FileMode.TYPE_TREE;
  
  import java.io.IOException;
  import java.text.MessageFormat;
  import java.util.Arrays;
  
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.ObjectReader;
  import org.eclipse.jgit.treewalk.CanonicalTreeParser;
  
  /**
   * Updates a {@link DirCache} by adding individual {@link DirCacheEntry}s.
   * <p>
   * A builder always starts from a clean slate and appends in every single
   * <code>DirCacheEntry</code> which the final updated index must have to reflect
   * its new content.
   * <p>
   * For maximum performance applications should add entries in path name order.
   * Adding entries out of order is permitted, however a final sorting pass will
   * be implicitly performed during {@link #finish()} to correct any out-of-order
   * entries. Duplicate detection is also delayed until the sorting is complete.
   *
   * @see DirCacheEditor
   */
  public class DirCacheBuilder extends BaseDirCacheEditor {
  	private boolean sorted;
  
  	/**
  	 * Construct a new builder.
  	 *
  	 * @param dc
  	 *            the cache this builder will eventually update.
  	 * @param ecnt
  	 *            estimated number of entries the builder will have upon
  	 *            completion. This sizes the initial entry table.
  	 */
  	protected DirCacheBuilder(final DirCache dc, final int ecnt) {
  		super(dc, ecnt);
  	}
  
  	/**
  	 * Append one entry into the resulting entry list.
  	 * <p>
  	 * The entry is placed at the end of the entry list. If the entry causes the
  	 * list to now be incorrectly sorted a final sorting phase will be
  	 * automatically enabled within {@link #finish()}.
  	 * <p>
  	 * The internal entry table is automatically expanded if there is
  	 * insufficient space for the new addition.
  	 *
  	 * @param newEntry
 	 *            the new entry to add.
 	 * @throws IllegalArgumentException
 	 *             If the FileMode of the entry was not set by the caller.
 	 */
 	public void add(final DirCacheEntry newEntry) {
 		if (newEntry.getRawMode() == 0)
 			throw new IllegalArgumentException(MessageFormat.format(
 					JGitText.get().fileModeNotSetForPath,
 					newEntry.getPathString()));
 		beforeAdd(newEntry);
 		fastAdd(newEntry);
 	}
 
 	/**
 	 * Add a range of existing entries from the destination cache.
 	 * <p>
 	 * The entries are placed at the end of the entry list. If any of the
 	 * entries causes the list to now be incorrectly sorted a final sorting
 	 * phase will be automatically enabled within {@link #finish()}.
 	 * <p>
 	 * This method copies from the destination cache, which has not yet been
 	 * updated with this editor's new table. So all offsets into the destination
 	 * cache are not affected by any updates that may be currently taking place
 	 * in this editor.
 	 * <p>
 	 * The internal entry table is automatically expanded if there is
 	 * insufficient space for the new additions.
 	 *
 	 * @param pos
 	 *            first entry to copy from the destination cache.
 	 * @param cnt
 	 *            number of entries to copy.
 	 */
 	public void keep(final int pos, int cnt) {
 		beforeAdd(cache.getEntry(pos));
 		fastKeep(pos, cnt);
 	}
 
 	/**
 	 * Recursively add an entire tree into this builder.
 	 * <p>
 	 * If pathPrefix is "a/b" and the tree contains file "c" then the resulting
 	 * DirCacheEntry will have the path "a/b/c".
 	 * <p>
 	 * All entries are inserted at stage 0, therefore assuming that the
 	 * application will not insert any other paths with the same pathPrefix.
 	 *
 	 * @param pathPrefix
 	 *            UTF-8 encoded prefix to mount the tree's entries at. If the
 	 *            path does not end with '/' one will be automatically inserted
 	 *            as necessary.
 	 * @param stage
 	 *            stage of the entries when adding them.
 	 * @param reader
 	 *            reader the tree(s) will be read from during recursive
 	 *            traversal. This must be the same repository that the resulting
 	 *            DirCache would be written out to (or used in) otherwise the
 	 *            caller is simply asking for deferred MissingObjectExceptions.
 	 *            Caller is responsible for releasing this reader when done.
 	 * @param tree
 	 *            the tree to recursively add. This tree's contents will appear
 	 *            under <code>pathPrefix</code>. The ObjectId must be that of a
 	 *            tree; the caller is responsible for dereferencing a tag or
 	 *            commit (if necessary).
 	 * @throws IOException
 	 *             a tree cannot be read to iterate through its entries.
 	 */
 	public void addTree(byte[] pathPrefix, int stage, ObjectReader reader,
 			AnyObjectId tree) throws IOException {
 		CanonicalTreeParser p = createTreeParser(pathPrefix, reader, tree);
 		while (!p.eof()) {
 			if (isTree(p)) {
 				p = enterTree(p, reader);
 				continue;
 			}
 
 			DirCacheEntry first = toEntry(stage, p);
 			beforeAdd(first);
 			fastAdd(first);
 			p = p.next();
 			break;
 		}
 
 		// Rest of tree entries are correctly sorted; use fastAdd().
 		while (!p.eof()) {
 			if (isTree(p)) {
 				p = enterTree(p, reader);
 			} else {
 				fastAdd(toEntry(stage, p));
 				p = p.next();
 			}
 		}
 	}
 
 	private static CanonicalTreeParser createTreeParser(byte[] pathPrefix,
 			ObjectReader reader, AnyObjectId tree) throws IOException {
 		return new CanonicalTreeParser(pathPrefix, reader, tree);
 	}
 
 	private static boolean isTree(CanonicalTreeParser p) {
 		return (p.getEntryRawMode() & TYPE_MASK) == TYPE_TREE;
 	}
 
 	private static CanonicalTreeParser enterTree(CanonicalTreeParser p,
 			ObjectReader reader) throws IOException {
 		p = p.createSubtreeIterator(reader);
 		return p.eof() ? p.next() : p;
 	}
 
 	private static DirCacheEntry toEntry(int stage, CanonicalTreeParser i) {
 		byte[] buf = i.getEntryPathBuffer();
 		int len = i.getEntryPathLength();
 		byte[] path = new byte[len];
 		System.arraycopy(buf, 0, path, 0, len);
 
 		DirCacheEntry e = new DirCacheEntry(path, stage);
 		e.setFileMode(i.getEntryRawMode());
 		e.setObjectIdFromRaw(i.idBuffer(), i.idOffset());
 		return e;
 	}
 
 	public void finish() {
 		if (!sorted)
 			resort();
 		replace();
 	}
 
 	private void beforeAdd(final DirCacheEntry newEntry) {
 		if (sorted && entryCnt > 0) {
 			final DirCacheEntry lastEntry = entries[entryCnt - 1];
 			final int cr = DirCache.cmp(lastEntry, newEntry);
 			if (cr > 0) {
 				// The new entry sorts before the old entry; we are
 				// no longer sorted correctly. We'll need to redo
 				// the sorting before we can close out the build.
 				//
 				sorted = false;
 			} else if (cr == 0) {
 				// Same file path; we can only insert this if the
 				// stages won't be violated.
 				//
 				final int peStage = lastEntry.getStage();
 				final int dceStage = newEntry.getStage();
 				if (peStage == dceStage)
 					throw bad(newEntry, JGitText.get().duplicateStagesNotAllowed);
 				if (peStage == 0 || dceStage == 0)
 					throw bad(newEntry, JGitText.get().mixedStagesNotAllowed);
 				if (peStage > dceStage)
 					sorted = false;
 			}
 		}
 	}
 
 	private void resort() {
 		Arrays.sort(entries, 0, entryCnt, DirCache.ENT_CMP);
 
 		for (int entryIdx = 1; entryIdx < entryCnt; entryIdx++) {
 			final DirCacheEntry pe = entries[entryIdx - 1];
 			final DirCacheEntry ce = entries[entryIdx];
 			final int cr = DirCache.cmp(pe, ce);
 			if (cr == 0) {
 				// Same file path; we can only allow this if the stages
 				// are 1-3 and no 0 exists.
 				//
 				final int peStage = pe.getStage();
 				final int ceStage = ce.getStage();
 				if (peStage == ceStage)
 					throw bad(ce, JGitText.get().duplicateStagesNotAllowed);
 				if (peStage == 0 || ceStage == 0)
 					throw bad(ce, JGitText.get().mixedStagesNotAllowed);
 			}
 		}
 
 		sorted = true;
 	}
 
 	private static IllegalStateException bad(DirCacheEntry a, String msg) {
 		return new IllegalStateException(String.format(
 				"%s: %d %s", //$NON-NLS-1$
 				msg, Integer.valueOf(a.getStage()), a.getPathString()));
 	}
 }