/*
 * 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 Also:
Git documentation about apply
Since:
2.0/**
 * 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.
Params:
repo – /**
	 * Constructs the command if the patch is to be applied to the index.
	 *
	 * @param repo
	 */
	ApplyCommand(Repository repo) {
		super(repo);
	}

	
Set patch
Params:
in – 
           the patch to apply
Returns:
this instance/**
	 * Set patch
	 *
	 * @param in
	 *            the patch to apply
	 * @return this instance
	 */
	public ApplyCommand setPatch(InputStream in) {
		checkCallable();
		this.in = in;
		return this;
	}

	
{@inheritDoc}
 Executes the ApplyCommand command with all the options and parameters collected by the setter methods (e.g. 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. /**
	 * {@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 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;
	}

	
Params:
f – 
fh – 
Throws:
IOException – 
PatchApplyException – /**
	 * @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"); //$NON-NLS-1$
	}
}