/*
    * Copyright (C) 2008, 2009, Google Inc.
    * Copyright (C) 2008, 2020 Shawn O. Pearce <spearce@spearce.org> 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.dircache;
  
  import static org.eclipse.jgit.dircache.DirCache.cmp;
  import static org.eclipse.jgit.dircache.DirCacheTree.peq;
  import static org.eclipse.jgit.lib.FileMode.TYPE_TREE;
  
  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;
  import org.eclipse.jgit.util.Paths;
  
  /**
   * Updates a {@link org.eclipse.jgit.dircache.DirCache} by supplying discrete
   * edit commands.
   * <p>
   * An editor updates a DirCache by taking a list of
   * {@link org.eclipse.jgit.dircache.DirCacheEditor.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 org.eclipse.jgit.dircache.DirCacheBuilder}.
   * <p>
   *
   * @see DirCacheBuilder
   */
  public class DirCacheEditor extends BaseDirCacheEditor {
  	private static final Comparator<PathEdit> EDIT_CMP = (PathEdit o1,
  			PathEdit o2) -> {
  		final byte[] a = o1.path;
  		final byte[] b = o2.path;
  		return cmp(a, a.length, b, b.length);
  	};
  
  	private final List<PathEdit> edits;
  	private int editIdx;
  
  	/**
  	 * 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(DirCache dc, int ecnt) {
  		super(dc, ecnt);
  		edits = new ArrayList<>();
  	}
  
  	/**
  	 * 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(PathEdit edit) {
  		edits.add(edit);
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public boolean commit() throws IOException {
  		if (edits.isEmpty()) {
  			// No changes? Don't rewrite the index.
  			//
  			cache.unlock();
  			return true;
  		}
  		return super.commit();
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public void finish() {
  		if (!edits.isEmpty()) {
  			applyEdits();
 			replace();
 		}
 	}
 
 	private void applyEdits() {
 		Collections.sort(edits, EDIT_CMP);
 		editIdx = 0;
 
 		final int maxIdx = cache.getEntryCount();
 		int lastIdx = 0;
 		while (editIdx < edits.size()) {
 			PathEdit e = edits.get(editIdx++);
 			int eIdx = cache.findEntry(lastIdx, 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);
 
 			if (e instanceof DeletePath) {
 				lastIdx = missing ? eIdx : cache.nextEntry(eIdx);
 				continue;
 			}
 			if (e instanceof DeleteTree) {
 				lastIdx = cache.nextEntry(e.path, e.path.length, eIdx);
 				continue;
 			}
 
 			if (missing) {
 				DirCacheEntry ent = new DirCacheEntry(e.path);
 				e.apply(ent);
 				if (ent.getRawMode() == 0) {
 					throw new IllegalArgumentException(MessageFormat.format(
 							JGitText.get().fileModeNotSetForPath,
 							ent.getPathString()));
 				}
 				lastIdx = e.replace
 					? deleteOverlappingSubtree(ent, eIdx)
 					: eIdx;
 				fastAdd(ent);
 			} else {
 				lastIdx = cache.nextEntry(eIdx);
 				if (lastIdx > eIdx + 1) {
 					// Apply to all entries of the current path (different
 					// stages). If any apply() resets the stage to STAGE_0, take
 					// only that entry and omit all others.
 					DirCacheEntry[] tmp = new DirCacheEntry[lastIdx - eIdx];
 					int n = 0;
 					for (int i = eIdx; i < lastIdx; i++) {
 						DirCacheEntry ent = cache.getEntry(i);
 						e.apply(ent);
 						if (ent.getStage() == DirCacheEntry.STAGE_0) {
 							fastAdd(ent);
 							n = 0;
 							break;
 						}
 						tmp[n++] = ent;
 					}
 					for (int i = 0; i < n; i++) {
 						fastAdd(tmp[i]);
 					}
 				} else {
 					DirCacheEntry ent = cache.getEntry(eIdx);
 					e.apply(ent);
 					fastAdd(ent);
 				}
 			}
 		}
 
 		final int cnt = maxIdx - lastIdx;
 		if (cnt > 0)
 			fastKeep(lastIdx, cnt);
 	}
 
 	private int deleteOverlappingSubtree(DirCacheEntry ent, int eIdx) {
 		byte[] entPath = ent.path;
 		int entLen = entPath.length;
 
 		// Delete any file that was previously processed and overlaps
 		// the parent directory for the new entry. Since the editor
 		// always processes entries in path order, binary search back
 		// for the overlap for each parent directory.
 		for (int p = pdir(entPath, entLen); p > 0; p = pdir(entPath, p)) {
 			int i = findEntry(entPath, p);
 			if (i >= 0) {
 				// A file does overlap, delete the file from the array.
 				// No other parents can have overlaps as the file should
 				// have taken care of that itself.
 				int n = --entryCnt - i;
 				System.arraycopy(entries, i + 1, entries, i, n);
 				break;
 			}
 
 			// If at least one other entry already exists in this parent
 			// directory there is no need to continue searching up the tree.
 			i = -(i + 1);
 			if (i < entryCnt && inDir(entries[i], entPath, p)) {
 				break;
 			}
 		}
 
 		int maxEnt = cache.getEntryCount();
 		if (eIdx >= maxEnt) {
 			return maxEnt;
 		}
 
 		DirCacheEntry next = cache.getEntry(eIdx);
 		if (Paths.compare(next.path, 0, next.path.length, 0,
 				entPath, 0, entLen, TYPE_TREE) < 0) {
 			// Next DirCacheEntry sorts before new entry as tree. Defer a
 			// DeleteTree command to delete any entries if they exist. This
 			// case only happens for A, A.c, A/c type of conflicts (rare).
 			insertEdit(new DeleteTree(entPath));
 			return eIdx;
 		}
 
 		// Next entry may be contained by the entry-as-tree, skip if so.
 		while (eIdx < maxEnt && inDir(cache.getEntry(eIdx), entPath, entLen)) {
 			eIdx++;
 		}
 		return eIdx;
 	}
 
 	private int findEntry(byte[] p, int pLen) {
 		int low = 0;
 		int high = entryCnt;
 		while (low < high) {
 			int mid = (low + high) >>> 1;
 			int cmp = cmp(p, pLen, entries[mid]);
 			if (cmp < 0) {
 				high = mid;
 			} else if (cmp == 0) {
 				while (mid > 0 && cmp(p, pLen, entries[mid - 1]) == 0) {
 					mid--;
 				}
 				return mid;
 			} else {
 				low = mid + 1;
 			}
 		}
 		return -(low + 1);
 	}
 
 	private void insertEdit(DeleteTree d) {
 		for (int i = editIdx; i < edits.size(); i++) {
 			int cmp = EDIT_CMP.compare(d, edits.get(i));
 			if (cmp < 0) {
 				edits.add(i, d);
 				return;
 			} else if (cmp == 0) {
 				return;
 			}
 		}
 		edits.add(d);
 	}
 
 	private static boolean inDir(DirCacheEntry e, byte[] path, int pLen) {
 		return e.path.length > pLen && e.path[pLen] == '/'
 				&& peq(path, e.path, pLen);
 	}
 
 	private static int pdir(byte[] path, int e) {
 		for (e--; e > 0; e--) {
 			if (path[e] == '/') {
 				return e;
 			}
 		}
 		return 0;
 	}
 
 	/**
 	 * 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. If any of these calls
 	 * resets the stage to 0, only this entry will be taken and entries for
 	 * other stages are discarded.
 	 */
 	public abstract static class PathEdit {
 		final byte[] path;
 		boolean replace = true;
 
 		/**
 		 * Create a new update command by path name.
 		 *
 		 * @param entryPath
 		 *            path of the file within the repository.
 		 */
 		public PathEdit(String entryPath) {
 			path = Constants.encode(entryPath);
 		}
 
 		PathEdit(byte[] path) {
 			this.path = path;
 		}
 
 		/**
 		 * 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(DirCacheEntry ent) {
 			path = ent.path;
 		}
 
 		/**
 		 * Configure if a file can replace a directory (or vice versa).
 		 * <p>
 		 * Default is {@code true} as this is usually the desired behavior.
 		 *
 		 * @param ok
 		 *            if true a file can replace a directory, or a directory can
 		 *            replace a file.
 		 * @return {@code this}
 		 * @since 4.2
 		 */
 		public PathEdit setReplace(boolean ok) {
 			replace = ok;
 			return this;
 		}
 
 		/**
 		 * 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);
 
 		@Override
 		public String toString() {
 			String p = DirCacheEntry.toString(path);
 			return getClass().getSimpleName() + '[' + p + ']';
 		}
 	}
 
 	/**
 	 * 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(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(DirCacheEntry ent) {
 			super(ent);
 		}
 
 		@Override
 		public void apply(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(String entryPath) {
 			super(entryPath.isEmpty()
 					|| entryPath.charAt(entryPath.length() - 1) == '/'
 					? entryPath
 					: entryPath + '/');
 		}
 
 		DeleteTree(byte[] path) {
 			super(appendSlash(path));
 		}
 
 		private static byte[] appendSlash(byte[] path) {
 			int n = path.length;
 			if (n > 0 && path[n - 1] != '/') {
 				byte[] r = new byte[n + 1];
 				System.arraycopy(path, 0, r, 0, n);
 				r[n] = '/';
 				return r;
 			}
 			return path;
 		}
 
 		@Override
 		public void apply(DirCacheEntry ent) {
 			throw new UnsupportedOperationException(JGitText.get().noApplyInDelete);
 		}
 	}
 }