/*
    * Copyright (C) 2011, Tomasz Zarna <Tomasz.Zarna@pl.ibm.com> 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.api;
  
  import static org.eclipse.jgit.lib.Constants.HEAD;
  
  import java.io.BufferedOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.List;
  
  import org.eclipse.jgit.api.errors.GitAPIException;
  import org.eclipse.jgit.api.errors.JGitInternalException;
  import org.eclipse.jgit.api.errors.NoHeadException;
  import org.eclipse.jgit.diff.DiffEntry;
  import org.eclipse.jgit.diff.DiffFormatter;
  import org.eclipse.jgit.dircache.DirCacheIterator;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.NullProgressMonitor;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectReader;
  import org.eclipse.jgit.lib.ProgressMonitor;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.treewalk.AbstractTreeIterator;
  import org.eclipse.jgit.treewalk.CanonicalTreeParser;
  import org.eclipse.jgit.treewalk.FileTreeIterator;
  import org.eclipse.jgit.treewalk.filter.TreeFilter;
  import org.eclipse.jgit.util.io.NullOutputStream;
  
  /**
   * Show changes between commits, commit and working tree, etc.
   *
   * @see <a href="http://www.kernel.org/pub/software/scm/git/docs/git-diff.html"
   *      >Git documentation about diff</a>
   */
  public class DiffCommand extends GitCommand<List<DiffEntry>> {
  	private AbstractTreeIterator oldTree;
  
  	private AbstractTreeIterator newTree;
  
  	private boolean cached;
  
  	private TreeFilter pathFilter = TreeFilter.ALL;
  
  	private boolean showNameAndStatusOnly;
  
  	private boolean showNameOnly;
  
  	private OutputStream out;
  
  	private int contextLines = -1;
  
  	private String sourcePrefix;
  
  	private String destinationPrefix;
  
  	private ProgressMonitor monitor = NullProgressMonitor.INSTANCE;
  
  	/**
  	 * Constructor for DiffCommand
  	 *
  	 * @param repo
  	 *            a {@link org.eclipse.jgit.lib.Repository} object.
  	 */
  	protected DiffCommand(Repository repo) {
  		super(repo);
  	}
  
  	private DiffFormatter getDiffFormatter() {
  		return out != null && !showNameAndStatusOnly && !showNameOnly
  				? new DiffFormatter(new BufferedOutputStream(out))
  				: new DiffFormatter(NullOutputStream.INSTANCE);
  	}
  
  	/**
  	 * {@inheritDoc}
  	 * <p>
  	 * Executes the {@code Diff} command with all the options and parameters
  	 * collected by the setter methods (e.g. {@link #setCached(boolean)} of this
  	 * class. Each instance of this class should only be used for one invocation
  	 * of the command. Don't call this method twice on an instance.
  	 */
  	@Override
  	public List<DiffEntry> call() throws GitAPIException {
  		try (DiffFormatter diffFmt = getDiffFormatter()) {
  			diffFmt.setRepository(repo);
  			diffFmt.setProgressMonitor(monitor);
  			if (cached) {
  				if (oldTree == null) {
  					ObjectId head = repo.resolve(HEAD + "^{tree}"); //$NON-NLS-1$
  					if (head == null)
  						throw new NoHeadException(JGitText.get().cannotReadTree);
 					CanonicalTreeParser p = new CanonicalTreeParser();
 					try (ObjectReader reader = repo.newObjectReader()) {
 						p.reset(reader, head);
 					}
 					oldTree = p;
 				}
 				newTree = new DirCacheIterator(repo.readDirCache());
 			} else {
 				if (oldTree == null) {
 					oldTree = new DirCacheIterator(repo.readDirCache());
 				}
 				if (newTree == null) {
 					newTree = new FileTreeIterator(repo);
 				}
 			}
 
 			diffFmt.setPathFilter(pathFilter);
 
 			List<DiffEntry> result = diffFmt.scan(oldTree, newTree);
 			if (showNameAndStatusOnly || showNameOnly) {
 				return result;
 			}
 			if (contextLines >= 0) {
 				diffFmt.setContext(contextLines);
 			}
 			if (destinationPrefix != null) {
 				diffFmt.setNewPrefix(destinationPrefix);
 			}
 			if (sourcePrefix != null) {
 				diffFmt.setOldPrefix(sourcePrefix);
 			}
 			diffFmt.format(result);
 			diffFmt.flush();
 			return result;
 		} catch (IOException e) {
 			throw new JGitInternalException(e.getMessage(), e);
 		}
 	}
 
 	/**
 	 * Whether to view the changes staged for the next commit
 	 *
 	 * @param cached
 	 *            whether to view the changes staged for the next commit
 	 * @return this instance
 	 */
 	public DiffCommand setCached(boolean cached) {
 		this.cached = cached;
 		return this;
 	}
 
 	/**
 	 * Set path filter
 	 *
 	 * @param pathFilter
 	 *            parameter, used to limit the diff to the named path
 	 * @return this instance
 	 */
 	public DiffCommand setPathFilter(TreeFilter pathFilter) {
 		this.pathFilter = pathFilter;
 		return this;
 	}
 
 	/**
 	 * Set old tree
 	 *
 	 * @param oldTree
 	 *            the previous state
 	 * @return this instance
 	 */
 	public DiffCommand setOldTree(AbstractTreeIterator oldTree) {
 		this.oldTree = oldTree;
 		return this;
 	}
 
 	/**
 	 * Set new tree
 	 *
 	 * @param newTree
 	 *            the updated state
 	 * @return this instance
 	 */
 	public DiffCommand setNewTree(AbstractTreeIterator newTree) {
 		this.newTree = newTree;
 		return this;
 	}
 
 	/**
 	 * Set whether to return only names and status of changed files
 	 *
 	 * @param showNameAndStatusOnly
 	 *            whether to return only names and status of changed files
 	 * @return this instance
 	 */
 	public DiffCommand setShowNameAndStatusOnly(boolean showNameAndStatusOnly) {
 		this.showNameAndStatusOnly = showNameAndStatusOnly;
 		return this;
 	}
 
 	/**
 	 * Set whether to return only names of changed files
 	 *
 	 * @param showNameOnly
 	 *            whether to return only names files
 	 * @return this instance
 	 * @since 6.4
 	 */
 	public DiffCommand setShowNameOnly(boolean showNameOnly) {
 		this.showNameOnly = showNameOnly;
 		return this;
 	}
 
 	/**
 	 * Set output stream
 	 *
 	 * @param out
 	 *            the stream to write line data
 	 * @return this instance
 	 */
 	public DiffCommand setOutputStream(OutputStream out) {
 		this.out = out;
 		return this;
 	}
 
 	/**
 	 * Set number of context lines instead of the usual three.
 	 *
 	 * @param contextLines
 	 *            the number of context lines
 	 * @return this instance
 	 */
 	public DiffCommand setContextLines(int contextLines) {
 		this.contextLines = contextLines;
 		return this;
 	}
 
 	/**
 	 * Set the given source prefix instead of "a/".
 	 *
 	 * @param sourcePrefix
 	 *            the prefix
 	 * @return this instance
 	 */
 	public DiffCommand setSourcePrefix(String sourcePrefix) {
 		this.sourcePrefix = sourcePrefix;
 		return this;
 	}
 
 	/**
 	 * Set the given destination prefix instead of "b/".
 	 *
 	 * @param destinationPrefix
 	 *            the prefix
 	 * @return this instance
 	 */
 	public DiffCommand setDestinationPrefix(String destinationPrefix) {
 		this.destinationPrefix = destinationPrefix;
 		return this;
 	}
 
 	/**
 	 * The progress monitor associated with the diff operation. By default, this
 	 * is set to <code>NullProgressMonitor</code>
 	 *
 	 * @see NullProgressMonitor
 	 * @param monitor
 	 *            a progress monitor
 	 * @return this instance
 	 */
 	public DiffCommand setProgressMonitor(ProgressMonitor monitor) {
 		if (monitor == null) {
 			monitor = NullProgressMonitor.INSTANCE;
 		}
 		this.monitor = monitor;
 		return this;
 	}
 }