/*
    * Copyright (C) 2008, 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.treewalk.filter;
  
  import java.io.IOException;
  
  import org.eclipse.jgit.dircache.DirCacheIterator;
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.treewalk.TreeWalk;
  import org.eclipse.jgit.treewalk.WorkingTreeIterator;
  
  /**
   * Selects interesting tree entries during walking.
   * <p>
   * This is an abstract interface. Applications may implement a subclass, or use
   * one of the predefined implementations already available within this package.
   * <p>
   * Unless specifically noted otherwise a TreeFilter implementation is not thread
   * safe and may not be shared by different TreeWalk instances at the same time.
   * This restriction allows TreeFilter implementations to cache state within
   * their instances during {@link #include(TreeWalk)} if it is beneficial to
   * their implementation. Deep clones created by {@link #clone()} may be used to
   * construct a thread-safe copy of an existing filter.
   *
   * <p>
   * <b>Path filters:</b>
   * <ul>
   * <li>Matching pathname:
   * {@link org.eclipse.jgit.treewalk.filter.PathFilter}</li>
   * </ul>
   *
   * <p>
   * <b>Difference filters:</b>
   * <ul>
   * <li>Only select differences: {@link #ANY_DIFF}.</li>
   * </ul>
   *
   * <p>
   * <b>Boolean modifiers:</b>
   * <ul>
   * <li>AND: {@link org.eclipse.jgit.treewalk.filter.AndTreeFilter}</li>
   * <li>OR: {@link org.eclipse.jgit.treewalk.filter.OrTreeFilter}</li>
   * <li>NOT: {@link org.eclipse.jgit.treewalk.filter.NotTreeFilter}</li>
   * </ul>
   */
  public abstract class TreeFilter {
  	/** Selects all tree entries. */
  	public static final TreeFilter ALL = new AllFilter();
  
  	private static final class AllFilter extends TreeFilter {
  		@Override
  		public boolean include(TreeWalk walker) {
  			return true;
  		}
  
  		@Override
  		public boolean shouldBeRecursive() {
  			return false;
  		}
  
  		@Override
  		public TreeFilter clone() {
  			return this;
  		}
  
  		@Override
  		public String toString() {
  			return "ALL"; //$NON-NLS-1$
  		}
  	}
  
  	/**
  	 * Selects only tree entries which differ between at least 2 trees.
  	 * <p>
  	 * This filter also prevents a TreeWalk from recursing into a subtree if all
  	 * parent trees have the identical subtree at the same path. This
  	 * dramatically improves walk performance as only the changed subtrees are
  	 * entered into.
  	 * <p>
  	 * If this filter is applied to a walker with only one tree it behaves like
  	 * {@link #ALL}, or as though the walker was matching a virtual empty tree
  	 * against the single tree it was actually given. Applications may wish to
  	 * treat such a difference as "all names added".
  	 * <p>
  	 * When comparing {@link WorkingTreeIterator} and {@link DirCacheIterator}
  	 * applications should use {@link IndexDiffFilter}.
  	 */
  	public static final TreeFilter ANY_DIFF = new AnyDiffFilter();
  
  	private static final class AnyDiffFilter extends TreeFilter {
 		private static final int baseTree = 0;
 
 		@Override
 		public boolean include(TreeWalk walker) {
 			final int n = walker.getTreeCount();
 			if (n == 1) // Assume they meant difference to empty tree.
 				return true;
 
 			final int m = walker.getRawMode(baseTree);
 			for (int i = 1; i < n; i++)
 				if (walker.getRawMode(i) != m || !walker.idEqual(i, baseTree))
 					return true;
 			return false;
 		}
 
 		@Override
 		public boolean shouldBeRecursive() {
 			return false;
 		}
 
 		@Override
 		public TreeFilter clone() {
 			return this;
 		}
 
 		@Override
 		public String toString() {
 			return "ANY_DIFF"; //$NON-NLS-1$
 		}
 	}
 
 	/**
 	 * Create a new filter that does the opposite of this filter.
 	 *
 	 * @return a new filter that includes tree entries this filter rejects.
 	 */
 	public TreeFilter negate() {
 		return NotTreeFilter.create(this);
 	}
 
 	/**
 	 * Determine if the current entry is interesting to report.
 	 * <p>
 	 * This method is consulted for subtree entries even if
 	 * {@link org.eclipse.jgit.treewalk.TreeWalk#isRecursive()} is enabled. The
 	 * consultation allows the filter to bypass subtree recursion on a
 	 * case-by-case basis, even when recursion is enabled at the application
 	 * level.
 	 *
 	 * @param walker
 	 *            the walker the filter needs to examine.
 	 * @return true if the current entry should be seen by the application;
 	 *         false to hide the entry.
 	 * @throws org.eclipse.jgit.errors.MissingObjectException
 	 *             an object the filter needs to consult to determine its answer
 	 *             does not exist in the Git repository the walker is operating
 	 *             on. Filtering this current walker entry is impossible without
 	 *             the object.
 	 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
 	 *             an object the filter needed to consult was not of the
 	 *             expected object type. This usually indicates a corrupt
 	 *             repository, as an object link is referencing the wrong type.
 	 * @throws java.io.IOException
 	 *             a loose object or pack file could not be read to obtain data
 	 *             necessary for the filter to make its decision.
 	 */
 	public abstract boolean include(TreeWalk walker)
 			throws MissingObjectException, IncorrectObjectTypeException,
 			IOException;
 
 	/**
 	 * Determine if the current entry is a parent, a match, or no match.
 	 * <p>
 	 * This method extends the result returned by {@link #include(TreeWalk)}
 	 * with a third option (-1), splitting the value true. This gives the
 	 * application a possibility to distinguish between an exact match and the
 	 * case when a subtree to the current entry might be a match.
 	 *
 	 * @param walker
 	 *            the walker the filter needs to examine.
 	 * @return -1 if the current entry is a parent of the filter but no exact
 	 *         match has been made; 0 if the current entry should be seen by the
 	 *         application; 1 if it should be hidden.
 	 * @throws org.eclipse.jgit.errors.MissingObjectException
 	 *             as thrown by {@link #include(TreeWalk)}
 	 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
 	 *             as thrown by {@link #include(TreeWalk)}
 	 * @throws java.io.IOException
 	 *             as thrown by {@link #include(TreeWalk)}
 	 * @since 4.7
 	 */
 	public int matchFilter(TreeWalk walker)
 			throws MissingObjectException, IncorrectObjectTypeException,
 			IOException
 	{
 		return include(walker) ? 0 : 1;
 	}
 
 	/**
 	 * Does this tree filter require a recursive walk to match everything?
 	 * <p>
 	 * If this tree filter is matching on full entry path names and its pattern
 	 * is looking for a '/' then the filter would require a recursive TreeWalk
 	 * to accurately make its decisions. The walker is not required to enable
 	 * recursive behavior for any particular filter, this is only a hint.
 	 *
 	 * @return true if the filter would like to have the walker recurse into
 	 *         subtrees to make sure it matches everything correctly; false if
 	 *         the filter does not require entering subtrees.
 	 */
 	public abstract boolean shouldBeRecursive();
 
 	/**
 	 * {@inheritDoc}
 	 *
 	 * Clone this tree filter, including its parameters.
 	 * <p>
 	 * This is a deep clone. If this filter embeds objects or other filters it
 	 * must also clone those, to ensure the instances do not share mutable data.
 	 */
 	@Override
 	public abstract TreeFilter clone();
 
 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		String n = getClass().getName();
 		int lastDot = n.lastIndexOf('.');
 		if (lastDot >= 0) {
 			n = n.substring(lastDot + 1);
 		}
 		return n.replace('$', '.');
 	}
 }