/*
    * Copyright (C) 2011, 2020 IBM Corporation 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 java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Writer;
  import java.nio.file.Files;
  import java.nio.file.StandardCopyOption;
  import java.text.MessageFormat;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  import org.eclipse.jgit.api.errors.GitAPIException;
  import org.eclipse.jgit.api.errors.PatchApplyException;
  import org.eclipse.jgit.api.errors.PatchFormatException;
  import org.eclipse.jgit.diff.DiffEntry.ChangeType;
  import org.eclipse.jgit.diff.RawText;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.FileMode;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.patch.FileHeader;
  import org.eclipse.jgit.patch.HunkHeader;
  import org.eclipse.jgit.patch.Patch;
  import org.eclipse.jgit.util.FileUtils;
  
  /**
   * Apply a patch to files and/or to the index.
   *
   * @see <a href="http://www.kernel.org/pub/software/scm/git/docs/git-apply.html"
   *      >Git documentation about apply</a>
   * @since 2.0
   */
  public class ApplyCommand extends GitCommand<ApplyResult> {
  
  	private InputStream in;
  
  	/**
  	 * Constructs the command if the patch is to be applied to the index.
  	 *
  	 * @param repo
  	 */
  	ApplyCommand(Repository repo) {
  		super(repo);
  	}
  
  	/**
  	 * Set patch
  	 *
  	 * @param in
  	 *            the patch to apply
  	 * @return this instance
  	 */
  	public ApplyCommand setPatch(InputStream in) {
  		checkCallable();
  		this.in = in;
  		return this;
  	}
  
  	/**
  	 * {@inheritDoc}
  	 * <p>
  	 * Executes the {@code ApplyCommand} command with all the options and
  	 * parameters collected by the setter methods (e.g.
  	 * {@link #setPatch(InputStream)} 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 ApplyResult call() throws GitAPIException, PatchFormatException,
  			PatchApplyException {
  		checkCallable();
  		ApplyResult r = new ApplyResult();
  		try {
  			final Patch/Patch.html#Patch">Patch p = new Patch();
  			try {
  				p.parse(in);
  			} finally {
  				in.close();
  			}
  			if (!p.getErrors().isEmpty())
  				throw new PatchFormatException(p.getErrors());
  			for (FileHeader fh : p.getFiles()) {
  				ChangeType type = fh.getChangeType();
  				File f = null;
  				switch (type) {
  				case ADD:
  					f = getFile(fh.getNewPath(), true);
  					apply(f, fh);
  					break;
 				case MODIFY:
 					f = getFile(fh.getOldPath(), false);
 					apply(f, fh);
 					break;
 				case DELETE:
 					f = getFile(fh.getOldPath(), false);
 					if (!f.delete())
 						throw new PatchApplyException(MessageFormat.format(
 								JGitText.get().cannotDeleteFile, f));
 					break;
 				case RENAME:
 					f = getFile(fh.getOldPath(), false);
 					File dest = getFile(fh.getNewPath(), false);
 					try {
 						FileUtils.mkdirs(dest.getParentFile(), true);
 						FileUtils.rename(f, dest,
 								StandardCopyOption.ATOMIC_MOVE);
 					} catch (IOException e) {
 						throw new PatchApplyException(MessageFormat.format(
 								JGitText.get().renameFileFailed, f, dest), e);
 					}
 					apply(dest, fh);
 					break;
 				case COPY:
 					f = getFile(fh.getOldPath(), false);
 					File target = getFile(fh.getNewPath(), false);
 					FileUtils.mkdirs(target.getParentFile(), true);
 					Files.copy(f.toPath(), target.toPath());
 					apply(target, fh);
 				}
 				r.addUpdatedFile(f);
 			}
 		} catch (IOException e) {
 			throw new PatchApplyException(MessageFormat.format(
 					JGitText.get().patchApplyException, e.getMessage()), e);
 		}
 		setCallable(false);
 		return r;
 	}
 
 	private File getFile(String path, boolean create)
 			throws PatchApplyException {
 		File f = new File(getRepository().getWorkTree(), path);
 		if (create)
 			try {
 				File parent = f.getParentFile();
 				FileUtils.mkdirs(parent, true);
 				FileUtils.createNewFile(f);
 			} catch (IOException e) {
 				throw new PatchApplyException(MessageFormat.format(
 						JGitText.get().createNewFileFailed, f), e);
 			}
 		return f;
 	}
 
 	/**
 	 * @param f
 	 * @param fh
 	 * @throws IOException
 	 * @throws PatchApplyException
 	 */
 	private void apply(File f, FileHeader fh)
 			throws IOException, PatchApplyException {
 		RawText rt = new RawText(f);
 		List<String> oldLines = new ArrayList<>(rt.size());
 		for (int i = 0; i < rt.size(); i++)
 			oldLines.add(rt.getString(i));
 		List<String> newLines = new ArrayList<>(oldLines);
 		int afterLastHunk = 0;
 		int lineNumberShift = 0;
 		int lastHunkNewLine = -1;
 		for (HunkHeader hh : fh.getHunks()) {
 
 			// We assume hunks to be ordered
 			if (hh.getNewStartLine() <= lastHunkNewLine) {
 				throw new PatchApplyException(MessageFormat
 						.format(JGitText.get().patchApplyException, hh));
 			}
 			lastHunkNewLine = hh.getNewStartLine();
 
 			byte[] b = new byte[hh.getEndOffset() - hh.getStartOffset()];
 			System.arraycopy(hh.getBuffer(), hh.getStartOffset(), b, 0,
 					b.length);
 			RawText hrt = new RawText(b);
 
 			List<String> hunkLines = new ArrayList<>(hrt.size());
 			for (int i = 0; i < hrt.size(); i++) {
 				hunkLines.add(hrt.getString(i));
 			}
 
 			if (hh.getNewStartLine() == 0) {
 				// Must be the single hunk for clearing all content
 				if (fh.getHunks().size() == 1
 						&& canApplyAt(hunkLines, newLines, 0)) {
 					newLines.clear();
 					break;
 				}
 				throw new PatchApplyException(MessageFormat
 						.format(JGitText.get().patchApplyException, hh));
 			}
 			// Hunk lines as reported by the hunk may be off, so don't rely on
 			// them.
 			int applyAt = hh.getNewStartLine() - 1 + lineNumberShift;
 			// But they definitely should not go backwards.
 			if (applyAt < afterLastHunk && lineNumberShift < 0) {
 				applyAt = hh.getNewStartLine() - 1;
 				lineNumberShift = 0;
 			}
 			if (applyAt < afterLastHunk) {
 				throw new PatchApplyException(MessageFormat
 						.format(JGitText.get().patchApplyException, hh));
 			}
 			boolean applies = false;
 			int oldLinesInHunk = hh.getLinesContext()
 					+ hh.getOldImage().getLinesDeleted();
 			if (oldLinesInHunk <= 1) {
 				// Don't shift hunks without context lines. Just try the
 				// position corrected by the current lineNumberShift, and if
 				// that fails, the position recorded in the hunk header.
 				applies = canApplyAt(hunkLines, newLines, applyAt);
 				if (!applies && lineNumberShift != 0) {
 					applyAt = hh.getNewStartLine() - 1;
 					applies = applyAt >= afterLastHunk
 							&& canApplyAt(hunkLines, newLines, applyAt);
 				}
 			} else {
 				int maxShift = applyAt - afterLastHunk;
 				for (int shift = 0; shift <= maxShift; shift++) {
 					if (canApplyAt(hunkLines, newLines, applyAt - shift)) {
 						applies = true;
 						applyAt -= shift;
 						break;
 					}
 				}
 				if (!applies) {
 					// Try shifting the hunk downwards
 					applyAt = hh.getNewStartLine() - 1 + lineNumberShift;
 					maxShift = newLines.size() - applyAt - oldLinesInHunk;
 					for (int shift = 1; shift <= maxShift; shift++) {
 						if (canApplyAt(hunkLines, newLines, applyAt + shift)) {
 							applies = true;
 							applyAt += shift;
 							break;
 						}
 					}
 				}
 			}
 			if (!applies) {
 				throw new PatchApplyException(MessageFormat
 						.format(JGitText.get().patchApplyException, hh));
 			}
 			// Hunk applies at applyAt. Apply it, and update afterLastHunk and
 			// lineNumberShift
 			lineNumberShift = applyAt - hh.getNewStartLine() + 1;
 			int sz = hunkLines.size();
 			for (int j = 1; j < sz; j++) {
 				String hunkLine = hunkLines.get(j);
 				switch (hunkLine.charAt(0)) {
 				case ' ':
 					applyAt++;
 					break;
 				case '-':
 					newLines.remove(applyAt);
 					break;
 				case '+':
 					newLines.add(applyAt++, hunkLine.substring(1));
 					break;
 				default:
 					break;
 				}
 			}
 			afterLastHunk = applyAt;
 		}
 		if (!isNoNewlineAtEndOfFile(fh)) {
 			newLines.add(""); //$NON-NLS-1$
 		}
 		if (!rt.isMissingNewlineAtEnd()) {
 			oldLines.add(""); //$NON-NLS-1$
 		}
 		if (!isChanged(oldLines, newLines)) {
 			return; // Don't touch the file
 		}
 		try (Writer fw = Files.newBufferedWriter(f.toPath())) {
 			for (Iterator<String> l = newLines.iterator(); l.hasNext();) {
 				fw.write(l.next());
 				if (l.hasNext()) {
 					// Don't bother handling line endings - if it was Windows,
 					// the \r is still there!
 					fw.write('\n');
 				}
 			}
 		}
 		getRepository().getFS().setExecute(f, fh.getNewMode() == FileMode.EXECUTABLE_FILE);
 	}
 
 	private boolean canApplyAt(List<String> hunkLines, List<String> newLines,
 			int line) {
 		int sz = hunkLines.size();
 		int limit = newLines.size();
 		int pos = line;
 		for (int j = 1; j < sz; j++) {
 			String hunkLine = hunkLines.get(j);
 			switch (hunkLine.charAt(0)) {
 			case ' ':
 			case '-':
 				if (pos >= limit
 						|| !newLines.get(pos).equals(hunkLine.substring(1))) {
 					return false;
 				}
 				pos++;
 				break;
 			default:
 				break;
 			}
 		}
 		return true;
 	}
 
 	private static boolean isChanged(List<String> ol, List<String> nl) {
 		if (ol.size() != nl.size())
 			return true;
 		for (int i = 0; i < ol.size(); i++)
 			if (!ol.get(i).equals(nl.get(i)))
 				return true;
 		return false;
 	}
 
 	private boolean isNoNewlineAtEndOfFile(FileHeader fh) {
 		List<? extends HunkHeader> hunks = fh.getHunks();
 		if (hunks == null || hunks.isEmpty()) {
 			return false;
 		}
 		HunkHeader lastHunk = hunks.get(hunks.size() - 1);
 		RawText lhrt = new RawText(lastHunk.getBuffer());
 		return lhrt.getString(lhrt.size() - 1)
 				.equals("\\ No newline at end of file"); //$NON-NLS-1$
 	}
 }