/*
    * Copyright (C) 2008, Google Inc. 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.patch;
  
  import static org.eclipse.jgit.lib.Constants.encodeASCII;
  import static org.eclipse.jgit.util.RawParseUtils.match;
  import static org.eclipse.jgit.util.RawParseUtils.nextLF;
  
  import java.nio.charset.Charset;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  
  import org.eclipse.jgit.lib.AbbreviatedObjectId;
  import org.eclipse.jgit.lib.FileMode;
  
  /**
   * A file in the Git "diff --cc" or "diff --combined" format.
   * <p>
   * A combined diff shows an n-way comparison between two or more ancestors and
   * the final revision. Its primary function is to perform code reviews on a
   * merge which introduces changes not in any ancestor.
   */
  public class CombinedFileHeader extends FileHeader {
  	private static final byte[] MODE = encodeASCII("mode "); //$NON-NLS-1$
  
  	private AbbreviatedObjectId[] oldIds;
  
  	private FileMode[] oldModes;
  
  	CombinedFileHeader(byte[] b, int offset) {
  		super(b, offset);
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	@SuppressWarnings("unchecked")
  	public List<? extends CombinedHunkHeader> getHunks() {
  		return (List<CombinedHunkHeader>) super.getHunks();
  	}
  
  	/**
  	 * {@inheritDoc}
  	 * <p>
  	 *
  	 * @return number of ancestor revisions mentioned in this diff.
  	 */
  	@Override
  	public int getParentCount() {
  		return oldIds.length;
  	}
  
  	/**
  	 * {@inheritDoc}
  	 * <p>
  	 * @return get the file mode of the first parent.
  	 */
  	@Override
  	public FileMode getOldMode() {
  		return getOldMode(0);
  	}
  
  	/**
  	 * Get the file mode of the nth ancestor
  	 *
  	 * @param nthParent
  	 *            the ancestor to get the mode of
  	 * @return the mode of the requested ancestor.
  	 */
  	public FileMode getOldMode(int nthParent) {
  		return oldModes[nthParent];
  	}
  
  	/**
  	 * {@inheritDoc}
  	 * <p>
  	 *
  	 * @return get the object id of the first parent.
  	 */
  	@Override
  	public AbbreviatedObjectId getOldId() {
  		return getOldId(0);
  	}
  
  	/**
  	 * Get the ObjectId of the nth ancestor
  	 *
  	 * @param nthParent
  	 *            the ancestor to get the object id of
  	 * @return the id of the requested ancestor.
  	 */
 	public AbbreviatedObjectId getOldId(int nthParent) {
 		return oldIds[nthParent];
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String getScriptText(Charset ocs, Charset ncs) {
 		final Charset[] cs = new Charset[getParentCount() + 1];
 		Arrays.fill(cs, ocs);
 		cs[getParentCount()] = ncs;
 		return getScriptText(cs);
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * <p>
 	 * Convert the patch script for this file into a string.
 	 */
 	@Override
 	public String getScriptText(Charset[] charsetGuess) {
 		return super.getScriptText(charsetGuess);
 	}
 
 	@Override
 	int parseGitHeaders(int ptr, int end) {
 		while (ptr < end) {
 			final int eol = nextLF(buf, ptr);
 			if (isHunkHdr(buf, ptr, end) >= 1) {
 				// First hunk header; break out and parse them later.
 				break;
 
 			} else if (match(buf, ptr, OLD_NAME) >= 0) {
 				parseOldName(ptr, eol);
 
 			} else if (match(buf, ptr, NEW_NAME) >= 0) {
 				parseNewName(ptr, eol);
 
 			} else if (match(buf, ptr, INDEX) >= 0) {
 				parseIndexLine(ptr + INDEX.length, eol);
 
 			} else if (match(buf, ptr, MODE) >= 0) {
 				parseModeLine(ptr + MODE.length, eol);
 
 			} else if (match(buf, ptr, NEW_FILE_MODE) >= 0) {
 				parseNewFileMode(ptr, eol);
 
 			} else if (match(buf, ptr, DELETED_FILE_MODE) >= 0) {
 				parseDeletedFileMode(ptr + DELETED_FILE_MODE.length, eol);
 
 			} else {
 				// Probably an empty patch (stat dirty).
 				break;
 			}
 
 			ptr = eol;
 		}
 		return ptr;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void parseIndexLine(int ptr, int eol) {
 		// "index $asha1,$bsha1..$csha1"
 		//
 		final List<AbbreviatedObjectId> ids = new ArrayList<>();
 		while (ptr < eol) {
 			final int comma = nextLF(buf, ptr, ',');
 			if (eol <= comma)
 				break;
 			ids.add(AbbreviatedObjectId.fromString(buf, ptr, comma - 1));
 			ptr = comma;
 		}
 
 		oldIds = new AbbreviatedObjectId[ids.size() + 1];
 		ids.toArray(oldIds);
 		final int dot2 = nextLF(buf, ptr, '.');
 		oldIds[ids.size()] = AbbreviatedObjectId.fromString(buf, ptr, dot2 - 1);
 		newId = AbbreviatedObjectId.fromString(buf, dot2 + 1, eol - 1);
 		oldModes = new FileMode[oldIds.length];
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected void parseNewFileMode(int ptr, int eol) {
 		for (int i = 0; i < oldModes.length; i++)
 			oldModes[i] = FileMode.MISSING;
 		super.parseNewFileMode(ptr, eol);
 	}
 
 	@Override
 	HunkHeader newHunkHeader(int offset) {
 		return new CombinedHunkHeader(this, offset);
 	}
 
 	private void parseModeLine(int ptr, int eol) {
 		// "mode $amode,$bmode..$cmode"
 		//
 		int n = 0;
 		while (ptr < eol) {
 			final int comma = nextLF(buf, ptr, ',');
 			if (eol <= comma)
 				break;
 			oldModes[n++] = parseFileMode(ptr, comma);
 			ptr = comma;
 		}
 		final int dot2 = nextLF(buf, ptr, '.');
 		oldModes[n] = parseFileMode(ptr, dot2);
 		newMode = parseFileMode(dot2 + 1, eol);
 	}
 
 	private void parseDeletedFileMode(int ptr, int eol) {
 		// "deleted file mode $amode,$bmode"
 		//
 		changeType = ChangeType.DELETE;
 		int n = 0;
 		while (ptr < eol) {
 			final int comma = nextLF(buf, ptr, ',');
 			if (eol <= comma)
 				break;
 			oldModes[n++] = parseFileMode(ptr, comma);
 			ptr = comma;
 		}
 		oldModes[n] = parseFileMode(ptr, eol);
 		newMode = FileMode.MISSING;
 	}
 }