Copyright (c) 2000, 2011 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2011 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.compare.internal.core.patch;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import org.eclipse.compare.patch.*;
import org.eclipse.core.runtime.Assert;

A Hunk describes a range of changed lines and some context lines.
/**
 * A Hunk describes a range of changed lines and some context lines.
 */
public class Hunk implements IHunk {
	private FilePatch2 fParent;
	private int fOldStart, fOldLength;
	private int fNewStart, fNewLength;
	private String[] fLines;
	private int hunkType;
	private String charset = null;

	public static Hunk createHunk(FilePatch2 parent, int[] oldRange, int[] newRange,
			List<String> lines, boolean hasLineAdditions, boolean hasLineDeletions, boolean hasContextLines) {
		int oldStart = 0;
		int oldLength = 0;
		int newStart = 0;
		int newLength = 0;
		if (oldRange[0] > 0)
			oldStart= oldRange[0]-1;	// line number start at 0!
		else
			oldStart= 0;
		oldLength= oldRange[1];
		if (newRange[0] > 0)
			newStart= newRange[0]-1;	// line number start at 0!
		else
			newStart= 0;
		newLength= newRange[1];
		int hunkType = FilePatch2.CHANGE;
		if (!hasContextLines) {
			if (hasLineAdditions && !hasLineDeletions) {
				hunkType = FilePatch2.ADDITION;
			} else if (!hasLineAdditions && hasLineDeletions) {
				hunkType = FilePatch2.DELETION;
			}
		}
		return new Hunk(parent, hunkType, oldStart, oldLength, newStart, newLength, lines.toArray(new String[lines.size()]));
	}

	public Hunk(FilePatch2 parent, int hunkType, int oldStart, int oldLength,
			int newStart, int newLength, String[] lines) {
		this.fParent = parent;
		if (this.fParent != null) {
			this.fParent.add(this);
		}
		this.hunkType = hunkType;
		this.fOldLength = oldLength;
		this.fOldStart = oldStart;
		this.fNewLength = newLength;
		this.fNewStart = newStart;
		this.fLines = lines;
	}

	public Hunk(FilePatch2 parent, Hunk toCopy) {
		this(parent, toCopy.hunkType, toCopy.fOldStart, toCopy.fOldLength, toCopy.fNewStart, toCopy.fNewLength, toCopy.fLines);
	}

	/*
	 * Returns the contents of this hunk.
	 * Each line starts with a control character. Their meaning is as follows:
	 * <ul>
	 * <li>
	 * '+': add the line
	 * <li>
	 * '-': delete the line
	 * <li>
	 * ' ': no change, context line
	 * </ul>
	 */
	public String getContent() {
		StringBuilder sb= new StringBuilder();
		for (String line : this.fLines) {
			sb.append(line.substring(0, LineReader.length(line)));
			sb.append('\n');
		}
		return sb.toString();
	}

	/*
	 * Returns a descriptive String for this hunk.
	 * It is in the form old_start,old_length -> new_start,new_length.
	 */
	String getDescription() {
		StringBuilder sb= new StringBuilder();
		sb.append(Integer.toString(this.fOldStart));
		sb.append(',');
		sb.append(Integer.toString(this.fOldLength));
		sb.append(" -> "); //$NON-NLS-1$
		sb.append(Integer.toString(this.fNewStart));
		sb.append(',');
		sb.append(Integer.toString(this.fNewLength));
		return sb.toString();
	}

	public String getRejectedDescription() {
		StringBuilder sb= new StringBuilder();
		sb.append("@@ -"); //$NON-NLS-1$
		sb.append(Integer.toString(this.fOldStart));
		sb.append(',');
		sb.append(Integer.toString(this.fOldLength));
		sb.append(" +"); //$NON-NLS-1$
		sb.append(Integer.toString(this.fNewStart));
		sb.append(',');
		sb.append(Integer.toString(this.fNewLength));
		sb.append(" @@"); //$NON-NLS-1$
		return sb.toString();
	}

	public int getHunkType(boolean reverse) {
		if (reverse) {
			if (this.hunkType == FilePatch2.ADDITION)
				return FilePatch2.DELETION;
			if (this.hunkType == FilePatch2.DELETION)
				return FilePatch2.ADDITION;
		}
		return this.hunkType;
	}

	void setHunkType(int hunkType) {
		this.hunkType = hunkType;
	}

	public String[] getLines() {
		return this.fLines;
	}

	@Override
	public String[] getUnifiedLines() {
		String[] ret = new String[this.fLines.length];
		System.arraycopy(this.fLines, 0, ret, 0, this.fLines.length);
		return ret;
	}

	
Set the parent of this hunk. This method should only be invoked from FilePatch2.add(Hunk) 
Params:
diff – the parent of this hunk/**
	 * Set the parent of this hunk. This method
	 * should only be invoked from {@link FilePatch2#add(Hunk)}
	 * @param diff the parent of this hunk
	 */
	void setParent(FilePatch2 diff) {
		if (this.fParent == diff)
			return;
		if (this.fParent != null)
			this.fParent.remove(this);
		this.fParent = diff;
	}

	public FilePatch2 getParent() {
		return this.fParent;
	}

	/*
	 * Tries to apply the given hunk on the specified lines.
	 * The parameter shift is added to the line numbers given
	 * in the hunk.
	 */
	public boolean tryPatch(PatchConfiguration configuration, List<String> lines, int shift, int fuzz) {
		boolean reverse = configuration.isReversed();
		int pos = getStart(reverse) + shift;
		List<String> contextLines = new ArrayList<>();
		boolean contextLinesMatched = true;
		boolean precedingLinesChecked = false;
		for (String s : this.fLines) {
			Assert.isTrue(s.length() > 0);
			String line = s.substring(1);
			char controlChar = s.charAt(0);

			if (controlChar == ' ') {	// context lines

				if (pos < 0 || pos >= lines.size())
					return false;
				contextLines.add(line);
				if (linesMatch(configuration, line, lines.get(pos))) {
					pos++;
					continue;
				} else if (fuzz > 0) {
					// doesn't match, use the fuzz factor
					contextLinesMatched = false;
					pos++;
					continue;
				}
				return false;
			} else if (isDeletedDelimeter(controlChar, reverse)) {
				// deleted lines

				if (precedingLinesChecked && !contextLinesMatched && contextLines.size() > 0)
					// context lines inside hunk don't match
					return false;

				// check following context lines if exist
				// use the fuzz factor if needed
				if (!precedingLinesChecked
						&& !contextLinesMatched
						&& contextLines.size() >= fuzz
						&& !checkPrecedingContextLines(configuration, lines,
								fuzz, pos, contextLines))
					return false;
				// else if there is less or equal context line to the fuzz
				// factor we ignore them all and treat as matching

				precedingLinesChecked = true;
				contextLines.clear();
				contextLinesMatched = true;

				if (pos < 0 || pos >= lines.size()) // out of the file
					return false;
				if (linesMatch(configuration, line, lines.get(pos))) {
					pos++;
					continue; // line matched, continue with the next one
				}

				// We must remove all lines at once, return false if this
				// fails. In other words, all lines considered for deletion
				// must be found one by one.
				return false;
			} else if (isAddedDelimeter(controlChar, reverse)) {

				if (precedingLinesChecked && !contextLinesMatched && contextLines.size() > 0)
					return false;

				if (!precedingLinesChecked
						&& !contextLinesMatched
						&& contextLines.size() >= fuzz
						&& !checkPrecedingContextLines(configuration, lines,
								fuzz, pos, contextLines))
					return false;

				precedingLinesChecked = true;
				contextLines.clear();
				contextLinesMatched = true;

				// we don't have to do anything more for a 'try'
			} else
				Assert.isTrue(false, "tryPatch: unknown control character: " + controlChar); //$NON-NLS-1$
		}

		// check following context lines if exist
		if (!contextLinesMatched
				&& fuzz > 0
				&& contextLines.size() > fuzz
				&& !checkFollowingContextLines(configuration, lines, fuzz, pos,
						contextLines))
			return false;

		return true;
	}

	private boolean checkPrecedingContextLines(
			PatchConfiguration configuration, List<String> lines, int fuzz, int pos,
			List<String> contextLines) {
		// ignore from the beginning
		for (int j = fuzz; j < contextLines.size(); j++) {
			if (!linesMatch(configuration, contextLines.get(j),
							lines.get(pos - contextLines.size() + j)))
				return false;
		}
		return true;
	}

	private boolean checkFollowingContextLines(
			PatchConfiguration configuration, List<String> lines, int fuzz, int pos,
			List<String> contextLines) {
		if (!contextLines.isEmpty()) {
			// ignore from the end
			for (int j = 0; j < contextLines.size() - fuzz; j++) {
				if (!linesMatch(configuration, contextLines.get(j),
						lines.get(pos - contextLines.size() + j)))
					return false;
			}
		}
		return true;
	}

	public int getStart(boolean after) {
		if (after) {
			return this.fNewStart;
		}
		return this.fOldStart;
	}

	public void setStart(int start, boolean after) {
		if (after) {
			this.fNewStart = start;
		} else {
			this.fOldStart = start;
		}
	}

	public int getLength(boolean after) {
		if (after) {
			return this.fNewLength;
		}
		return this.fOldLength;
	}

	private int getShift(boolean reverse) {
		if (reverse) {
			return this.fOldLength - this.fNewLength;
		}
		return this.fNewLength - this.fOldLength;
	}

	int doPatch(PatchConfiguration configuration, List<String> lines, int shift, int fuzz) {
		boolean reverse = configuration.isReversed();
		int pos = getStart(reverse) + shift;
		List<String> contextLines = new ArrayList<>();
		boolean contextLinesMatched = true;
		boolean precedingLinesChecked = false;
		String lineDelimiter = getLineDelimiter(lines);

		for (String s : this.fLines) {
			Assert.isTrue(s.length() > 0);
			String line= s.substring(1);
			char controlChar= s.charAt(0);
			if (controlChar == ' ') {
				// context lines
				Assert.isTrue(pos < lines.size(), "doPatch: inconsistency in context"); //$NON-NLS-1$
				contextLines.add(line);
				if (linesMatch(configuration, line, lines.get(pos))) {
					pos++;
					continue;
				} else if (fuzz > 0) {
					// doesn't match, use the fuzz factor
					contextLinesMatched = false;
					pos++;
					continue;
				}
				Assert.isTrue(false, "doPatch: context doesn't match"); //$NON-NLS-1$
//					pos++;
			} else if (isDeletedDelimeter(controlChar, reverse)) {
				// deleted lines
				if (precedingLinesChecked && !contextLinesMatched && contextLines.size() > 0)
					// context lines inside hunk don't match
					Assert.isTrue(false, "doPatch: context lines inside hunk don't match"); //$NON-NLS-1$

				// check following context lines if exist
				// use the fuzz factor if needed
				if (!precedingLinesChecked
						&& !contextLinesMatched
						&& contextLines.size() >= fuzz
						&& !checkPrecedingContextLines(configuration, lines,
								fuzz, pos, contextLines))
					Assert.isTrue(false, "doPatch: preceding context lines don't match, even though fuzz factor has been used"); //$NON-NLS-1$
				// else if there is less or equal context line to the fuzz
				// factor we ignore them all and treat as matching

				precedingLinesChecked = true;
				contextLines.clear();
				contextLinesMatched = true;

				lines.remove(pos);
			} else if (isAddedDelimeter(controlChar, reverse)) {
				// added lines
				if (precedingLinesChecked && !contextLinesMatched && contextLines.size() > 0)
					Assert.isTrue(false, "doPatch: context lines inside hunk don't match"); //$NON-NLS-1$

				if (!precedingLinesChecked
						&& !contextLinesMatched
						&& contextLines.size() >= fuzz
						&& !checkPrecedingContextLines(configuration, lines,
								fuzz, pos, contextLines))
					Assert.isTrue(false, "doPatch: preceding context lines don't match, even though fuzz factor has been used"); //$NON-NLS-1$

				precedingLinesChecked = true;
				contextLines.clear();
				contextLinesMatched = true;

				// if the line contains a delimiter, use a proper one
				if (line.length() > LineReader.length(line))
					line = line.substring(0, LineReader.length(line)) + lineDelimiter;

				if (getLength(reverse) == 0 && pos+1 < lines.size())
					lines.add(pos+1, line);
				else
					lines.add(pos, line);
				pos++;
			} else
				Assert.isTrue(false, "doPatch: unknown control character: " + controlChar); //$NON-NLS-1$
		}
		return getShift(reverse);
	}

	private boolean isDeletedDelimeter(char controlChar, boolean reverse) {
		return (!reverse && controlChar == '-') || (reverse && controlChar == '+');
	}

	private boolean isAddedDelimeter(char controlChar, boolean reverse) {
		return (reverse && controlChar == '-') || (!reverse && controlChar == '+');
	}

	/*
	 * Compares two strings.
	 * If fIgnoreWhitespace is true whitespace is ignored.
	 */
	private boolean linesMatch(PatchConfiguration configuration, String line1, String line2) {
		if (configuration.isIgnoreWhitespace())
			return stripWhiteSpace(line1).equals(stripWhiteSpace(line2));
		if (isIgnoreLineDelimiter()) {
			int l1= LineReader.length(line1);
			int l2= LineReader.length(line2);
			if (l1 != l2)
				return false;
			return line1.regionMatches(0, line2, 0, l1);
		}
		return line1.equals(line2);
	}

	private boolean isIgnoreLineDelimiter() {
		return true;
	}

	private String getLineDelimiter(List<String> lines) {
		if (lines.size() > 0) {
			// get a line separator from the file being patched
			String line0 = lines.get(0);
			return line0.substring(LineReader.length(line0));
		} else if (this.fLines.length > 0) {
			// if the file doesn't exist use a line separator from the patch
			return this.fLines[0].substring(LineReader.length(this.fLines[0]));
		}
		return System.getProperty("line.separator"); //$NON-NLS-1$
	}

	/*
	 * Returns the given string with all whitespace characters removed.
	 * Whitespace is defined by <code>Character.isWhitespace(...)</code>.
	 */
	private String stripWhiteSpace(String s) {
		StringBuilder sb= new StringBuilder();
		int l= s.length();
		for (int i= 0; i < l; i++) {
			char c= s.charAt(i);
			if (!Character.isWhitespace(c))
				sb.append(c);
		}
		return sb.toString();
	}

	public String getContents(boolean isAfterState, boolean reverse) {
		StringBuilder result= new StringBuilder();
		for (String line : this.fLines) {
			String rest= line.substring(1);
			char c = line.charAt(0);
			if (c == ' ') {
				result.append(rest);
			} else if (isDeletedDelimeter(c, reverse) && !isAfterState) {
				result.append(rest);
			} else if (isAddedDelimeter(c, reverse) && isAfterState) {
				result.append(rest);
			}
		}
		return result.toString();
	}

	@Override
	public String getLabel() {
		return getDescription();
	}

	@Override
	public int getStartPosition() {
		return getStart(false);
	}

	@Override
	public InputStream getOriginalContents() {
		String contents = getContents(false, false);
		return asInputStream(contents);
	}

	@Override
	public InputStream getPatchedContents() {
		String contents = getContents(true, false);
		return asInputStream(contents);
	}

	private InputStream asInputStream(String contents) {
		String charSet = getCharset();
		return FileDiffResult.asInputStream(contents, charSet);
	}

	void setCharset(String charset) {
		this.charset = charset;
	}

	
{@inheritDoc}
Deprecated:
This method can be called before the first attempt to apply the hunk when it is impossible to determine the encoding and in this case it always returns null. Please see IFilePatchResult.getCharset() as a proper way to obtain charset./**
	 * {@inheritDoc}
	 * @deprecated This method can be called before the first attempt to apply
	 *             the hunk when it is impossible to determine the encoding and
	 *             in this case it always returns null. Please see
	 *             {@link IFilePatchResult#getCharset()} as a proper way to
	 *             obtain charset.
	 */
	@Deprecated
	@Override
	public String getCharset() {
		return this.charset;
	}

}