Copyright (c) 2006, 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) 2006, 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.util.List;

import org.eclipse.compare.patch.IHunkFilter;
import org.eclipse.compare.patch.PatchConfiguration;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.OperationCanceledException;

public class HunkResult {

	private static final boolean DEBUG= false;

	
Default maximum fuzz factor equals 2. This is related to the default
number of context lines, which is 3.
/**
	 * Default maximum fuzz factor equals 2. This is related to the default
	 * number of context lines, which is 3.
	 */
	private static final int MAXIMUM_FUZZ_FACTOR = 2;

	private Hunk fHunk;
	private boolean fMatches;
	private int fShift;
	private int fFuzz = -1; // not set or couldn't be found

	private final FileDiffResult fDiffResult;

	
Create a hunk result for the given hunk
Params:
diffResult – the parent diff result
hunk – the hunk/**
	 * Create a hunk result for the given hunk
	 * @param diffResult the parent diff result
	 * @param hunk the hunk
	 */
	public HunkResult(FileDiffResult diffResult, Hunk hunk) {
		this.fDiffResult = diffResult;
		this.fHunk = hunk;
	}

	
Try to apply the specified hunk to the given lines.
If the hunk cannot be applied at the original position
the method tries shift lines up and down.
Params:
lines – the lines to be patched
Returns:
whether the hunk could be applied/**
	 * Try to apply the specified hunk to the given lines.
	 * If the hunk cannot be applied at the original position
	 * the method tries shift lines up and down.
	 * @param lines the lines to be patched
	 * @return whether the hunk could be applied
	 */
	public boolean patch(List<String> lines) {
		this.fMatches = false;
		PatchConfiguration configuration = getConfiguration();
		// if the fuzz is not set for the current hunk use the one from fDiffResult
		int fuzz = this.fFuzz != -1 ? this.fFuzz : configuration.getFuzz();
		if (isEnabled(configuration)) {
			if (this.fHunk.tryPatch(configuration, lines, this.fShift, fuzz)) {
				// it's a perfect match, no shifting is needed
				this.fShift += this.fHunk.doPatch(configuration, lines, this.fShift, fuzz);
				this.fMatches = true;
			} else {
				boolean found= false;
				int oldShift= this.fShift;

				int hugeShift = lines.size();
				for (int i = 1; i <= hugeShift; i++) {
					if (this.fHunk.tryPatch(configuration, lines, this.fShift - i, fuzz)) {
						if (isAdjustShift())
							this.fShift -= i;
						found = true;
						break;
					}
				}

				if (!found) {
					for (int i = 1; i <= hugeShift; i++) {
						if (this.fHunk.tryPatch(configuration, lines, this.fShift + i, fuzz)) {
							if (isAdjustShift())
								this.fShift += i;
							found = true;
							break;
						}
					}
				}

				if (found) {
					if (DEBUG) System.out.println("patched hunk at offset: " + (this.fShift-oldShift)); //$NON-NLS-1$
					this.fShift+= this.fHunk.doPatch(configuration, lines, this.fShift, fuzz);
					this.fMatches = true;
				}
			}
		}
		return this.fMatches;
	}

	private boolean isAdjustShift() {
		return true;
	}

	private PatchConfiguration getConfiguration() {
		return getDiffResult().getConfiguration();
	}

	
Calculate the fuzz that will allow the most hunks to be matched. Even
though we're interested only in the value of the fuzz, the shifting is
done anyway.
Params:
lines – 
           the lines of the target file
monitor – 
           a progress monitor
Returns:
the fuzz factor or -1 if the hunk could not be matched/**
	 * Calculate the fuzz that will allow the most hunks to be matched. Even
	 * though we're interested only in the value of the fuzz, the shifting is
	 * done anyway.
	 *
	 * @param lines
	 *            the lines of the target file
	 * @param monitor
	 *            a progress monitor
	 * @return the fuzz factor or -1 if the hunk could not be matched
	 */
	public int calculateFuzz(List<String> lines, IProgressMonitor monitor) {
		this.fMatches = false;
		PatchConfiguration configuration = getConfiguration();
		int fuzz = 0;
		int maxFuzz = configuration.getFuzz() == -1 ? MAXIMUM_FUZZ_FACTOR
				: configuration.getFuzz();
		for (; fuzz <= maxFuzz; fuzz++) {
			// try to apply using lines coordinates from the patch
			if (this.fHunk.tryPatch(configuration, lines, this.fShift, fuzz)) {
				// it's a perfect match, no adjustment is needed
				this.fShift += this.fHunk.doPatch(configuration, lines, this.fShift, fuzz);
				this.fMatches = true;
				break;
			}

			// TODO (tzarna): hugeShift=lines.size() is more than we need.
			// Lines to the beg/end of a file would be enough but this can still
			// in matching hunks out of order. Try to shift using only lines
			// available "between" hunks.
			int hugeShift = lines.size();

			// shift up
			for (int i = 1; i <= hugeShift; i++) {
				if (monitor.isCanceled()) {
					throw new OperationCanceledException();
				}
				if (this.fHunk.tryPatch(configuration, lines, this.fShift - i, fuzz)) {
					if (isAdjustShift())
						this.fShift -= i;
					this.fMatches = true;
					break;
				}
			}

			// shift down
			if (!this.fMatches) {
				for (int i = 1; i <= hugeShift; i++) {
					if (monitor.isCanceled()) {
						throw new OperationCanceledException();
					}
					if (this.fHunk.tryPatch(configuration, lines, this.fShift + i, fuzz)) {
						if (isAdjustShift())
							this.fShift += i;
						this.fMatches = true;
						break;
					}
				}
			}

			if (this.fMatches) {
				this.fShift += this.fHunk.doPatch(configuration, lines, this.fShift, fuzz);
				break;
			}
		}
		// set fuzz for the current hunk
		this.fFuzz = this.fMatches ? fuzz : -1;
		return this.fFuzz;
	}

	
Return the amount that this hunk should be shifted when a match with the file
is attempted. The shift is needed to compensate for previous hunks that have
been applied.
Returns:
the amount that this hunk should be shifted when applied/**
	 * Return the amount that this hunk should be shifted when a match with the file
	 * is attempted. The shift is needed to compensate for previous hunks that have
	 * been applied.
	 * @return the amount that this hunk should be shifted when applied
	 */
	public int getShift() {
		return this.fShift;
	}

	
Set the amount that this hunk should be shifted when a match with the file
is attempted. The shift is needed to compensate for previous hunks that have
been applied.
Params:
shift – the amount to shift this hunk/**
	 * Set the amount that this hunk should be shifted when a match with the file
	 * is attempted. The shift is needed to compensate for previous hunks that have
	 * been applied.
	 * @param shift the amount to shift this hunk
	 */
	public void setShift(int shift) {
		this.fShift = shift;
	}

	
Return the hunk to which this result applies.
Returns:
the hunk to which this result applies/**
	 * Return the hunk to which this result applies.
	 * @return the hunk to which this result applies
	 */
	public Hunk getHunk() {
		return this.fHunk;
	}

	
Return the parent diff result.
Returns:
the parent diff result/**
	 * Return the parent diff result.
	 * @return the parent diff result
	 */
	public FileDiffResult getDiffResult() {
		return this.fDiffResult;
	}

	
Return whether the hunk was matched with the target file.
Returns:
whether the hunk was matched with the target file/**
	 * Return whether the hunk was matched with the target file.
	 * @return whether the hunk was matched with the target file
	 */
	public boolean isOK() {
		return this.fMatches;
	}

	
Return the contents that should be displayed for the hunk result.
Params:
afterState – whether the after state or before state of the hunk is desired
fullContext – whether the hunk should be displayed with the entire file or
only the lines in the hunk itself
Returns:
the contents to be display/**
	 * Return the contents that should be displayed for the hunk result.
	 * @param afterState whether the after state or before state of the hunk is desired
	 * @param fullContext whether the hunk should be displayed with the entire file or
	 * only the lines in the hunk itself
	 * @return the contents to be display
	 */
	public String getContents(boolean afterState, boolean fullContext) {
		if (fullContext) {
			boolean problemFound = false;
			List<String> lines = getDiffResult().getBeforeLines();
			if (afterState) {
				if (isOK()) {
					int oldShift = this.fShift;
					try {
						this.fShift = 0;
						problemFound = !patch(lines);
					} finally {
						this.fShift = oldShift;
					}
				} else {
					problemFound = true;
				}
			}
			// Only return the full context if we could apply the hunk
			if (!problemFound)
				return LineReader.createString(this.fDiffResult.isPreserveLineDelimeters(), lines);
		}
		return getHunk().getContents(afterState, getConfiguration().isReversed());
	}

	private boolean isEnabled(PatchConfiguration configuration) {
		IHunkFilter[] filters = configuration.getHunkFilters();
		for (IHunkFilter filter : filters) {
			if (!filter.select(this.fHunk)) {
				return false;
			}
		}
		return true;
	}

	public void setMatches(boolean matches) {
		this.fMatches = matches;
	}

	public String getCharset() {
		return this.fDiffResult.getCharset();
	}

	public int getFuzz() {
		return this.fFuzz;
	}
}