<?php
/**
 * Text_Diff
 *
 * General API for generating and formatting diffs - the differences between
 * two sequences of strings.
 *
 * The PHP diff code used in this package was originally written by Geoffrey
 * T. Dairiki and is used with his permission.
 *
 * $Horde: framework/Text_Diff/Diff.php,v 1.8 2004/10/13 09:30:20 jan Exp $
 *
 * @package Text_Diff
 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
 */
class Text_Diff
{

	/**
	 * Array of changes.
	 *
	 * @var array $_edits
	 */
	var $_edits;

	/**
	 * Computes diffs between sequences of strings.
	 *
	 * @param array $from_lines  An array of strings.  Typically these are
	 *                           lines from a file.
	 * @param array $to_lines    An array of strings.
	 */
	function __construct($from_lines, $to_lines)
	{
		array_walk($from_lines, [$this, '_trimNewlines']);
		array_walk($to_lines, [$this, '_trimNewlines']);

		if (extension_loaded('xdiff')) {
			$engine = new Text_Diff_Engine_xdiff();
		} else {
			$engine = new Text_Diff_Engine_native();
		}

		$this->_edits = $engine->diff($from_lines, $to_lines);
	}

	/**
	 * Returns the array of differences.
	 */
	function getDiff()
	{
		return $this->_edits;
	}

	/**
	 * Computes a reversed diff.
	 *
	 * Example:
	 * <code>
	 * $diff = new Text_Diff($lines1, $lines2);
	 * $rev = $diff->reverse();
	 * </code>
	 *
	 * @return Text_Diff  A Diff object representing the inverse of the
	 *                    original diff.  Note that we purposely don't return a
	 *                    reference here, since this essentially is a clone()
	 *                    method.
	 */
	function reverse()
	{
		if (version_compare(zend_version(), '2', '>')) {
			$rev = clone($obj);
		} else {
			$rev = $this;
		}
		$rev->_edits = [];
		foreach ($this->_edits as $edit) {
			$rev->_edits[] = $edit->reverse();
		}
		return $rev;
	}

	/**
	 * Checks for an empty diff.
	 *
	 * @return boolean  True if two sequences were identical.
	 */
	function isEmpty()
	{
		foreach ($this->_edits as $edit) {
			if (! is_a($edit, 'Text_Diff_Op_copy')) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Computes the length of the Longest Common Subsequence (LCS).
	 *
	 * This is mostly for diagnostic purposed.
	 *
	 * @return int  The length of the LCS.
	 */
	function lcs()
	{
		$lcs = 0;
		foreach ($this->_edits as $edit) {
			if (is_a($edit, 'Text_Diff_Op_copy')) {
				$lcs += count($edit->orig);
			}
		}
		return $lcs;
	}

	/**
	 * Gets the original set of lines.
	 *
	 * This reconstructs the $from_lines parameter passed to the constructor.
	 *
	 * @return array  The original sequence of strings.
	 */
	function getOriginal()
	{
		$lines = [];
		foreach ($this->_edits as $edit) {
			if ($edit->orig) {
				array_splice($lines, count($lines), 0, $edit->orig);
			}
		}
		return $lines;
	}

	/**
	 * Gets the final set of lines.
	 *
	 * This reconstructs the $to_lines parameter passed to the constructor.
	 *
	 * @return array  The sequence of strings.
	 */
	function getFinal()
	{
		$lines = [];
		foreach ($this->_edits as $edit) {
			if ($edit->final) {
				array_splice($lines, count($lines), 0, $edit->final);
			}
		}
		return $lines;
	}

	/**
	 * Removes trailing newlines from a line of text. This is meant to be used
	 * with array_walk().
	 *
	 * @param string $line  The line to trim.
	 * @param integer $key  The index of the line in the array. Not used.
	 */
	function _trimNewlines(&$line, $key)
	{
		$line = str_replace(["\n", "\r", "\r\n"], '', $line);
	}

	/**
	 * Checks a diff for validity.
	 *
	 * This is here only for debugging purposes.
	 */
	function _check($from_lines, $to_lines)
	{
		if (serialize($from_lines) != serialize($this->getOriginal())) {
			trigger_error("Reconstructed original doesn't match", E_USER_ERROR);
		}
		if (serialize($to_lines) != serialize($this->getFinal())) {
			trigger_error("Reconstructed final doesn't match", E_USER_ERROR);
		}

		$rev = $this->reverse();
		if (serialize($to_lines) != serialize($rev->getOriginal())) {
			trigger_error("Reversed original doesn't match", E_USER_ERROR);
		}
		if (serialize($from_lines) != serialize($rev->getFinal())) {
			trigger_error("Reversed final doesn't match", E_USER_ERROR);
		}

		$prevtype = null;
		foreach ($this->_edits as $edit) {
			if ($prevtype == get_class($edit)) {
				trigger_error("Edit sequence is non-optimal", E_USER_ERROR);
			}
			$prevtype = get_class($edit);
		}

		return true;
	}
}

/**
 * $Horde: framework/Text_Diff/Diff.php,v 1.8 2004/10/13 09:30:20 jan Exp $
 *
 * @package Text_Diff
 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
 */
class Text_MappedDiff extends Text_Diff
{

	/**
	 * Computes a diff between sequences of strings.
	 *
	 * This can be used to compute things like case-insensitve diffs, or diffs
	 * which ignore changes in white-space.
	 *
	 * @param array $from_lines         An array of strings.
	 * @param array $to_lines           An array of strings.
	 * @param array $mapped_from_lines  This array should have the same size
	 *                                  number of elements as $from_lines.  The
	 *                                  elements in $mapped_from_lines and
	 *                                  $mapped_to_lines are what is actually
	 *                                  compared when computing the diff.
	 * @param array $mapped_to_lines    This array should have the same number
	 *                                  of elements as $to_lines.
	 */
	function __construct(
		$from_lines,
		$to_lines,
		$mapped_from_lines,
		$mapped_to_lines
	) {

//        assert(count($from_lines) == count($mapped_from_lines));
//        assert(count($to_lines) == count($mapped_to_lines));

		parent::__construct($mapped_from_lines, $mapped_to_lines);

		$xi = $yi = 0;
		for ($i = 0, $count_edits = count($this->edits); $i < $count_edits; $i++) {
			$orig = &$this->edits[$i]->orig;
			if (is_array($orig)) {
				$orig = array_slice($from_lines, $xi, count($orig));
				$xi += count($orig);
			}

			$final = &$this->edits[$i]->final;
			if (is_array($final)) {
				$final = array_slice($to_lines, $yi, count($final));
				$yi += count($final);
			}
		}
	}
}

/**
 * Class used internally by Diff to actually compute the diffs.  This class
 * uses the xdiff PECL package (http://pecl.php.net/package/xdiff) to compute
 * the differences between the two input arrays.
 *
 * @author  Jon Parise <jon@horde.org>
 * @package Text_Diff
 * @access  private
 */
class Text_Diff_Engine_xdiff
{
	function diff($from_lines, $to_lines)
	{
		/* Convert the two input arrays into strings for xdiff processing. */
		$from_string = implode("\n", $from_lines);
		$to_string = implode("\n", $to_lines);

		/* Diff the two strings and convert the result to an array. */
		$diff = xdiff_string_diff($from_string, $to_string, count($to_lines));
		$diff = explode("\n", $diff);

		/* Walk through the diff one line at a time.  We build the $edits
		 * array of diff operations by reading the first character of the
		 * xdiff output (which is in the "unified diff" format).
		 *
		 * Note that we don't have enough information to detect "changed"
		 * lines using this approach, so we can't add Text_Diff_Op_changed
		 * instances to the $edits array.  The result is still perfectly
		 * valid, albeit a little less descriptive and efficient. */
		$edits = [];
		foreach ($diff as $line) {
			switch ($line[0]) {
				case ' ':
					$edits[] = new Text_Diff_Op_copy([substr($line, 1)]);
					break;

				case '+':
					$edits[] = new Text_Diff_Op_add([substr($line, 1)]);
					break;

				case '-':
					$edits[] = new Text_Diff_Op_delete([substr($line, 1)]);
					break;
			}
		}

		return $edits;
	}
}

/**
 * Class used internally by Diff to actually compute the diffs.  This class is
 * implemented using native PHP code.
 *
 * The algorithm used here is mostly lifted from the perl module
 * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
 * http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
 *
 * More ideas are taken from:
 * http://www.ics.uci.edu/~eppstein/161/960229.html
 *
 * Some ideas (and a bit of code) are from from analyze.c, from GNU
 * diffutils-2.7, which can be found at:
 * ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
 *
 * Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from
 * Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this
 * code was writting by him, and is used/adapted with his permission.
 *
 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
 * @package Text_Diff
 * @access  private
 */
class Text_Diff_Engine_native
{

	function diff($from_lines, $to_lines)
	{
		$n_from = count($from_lines);
		$n_to = count($to_lines);

		$this->xchanged = $this->ychanged = [];
		$this->xv = $this->yv = [];
		$this->xind = $this->yind = [];
		unset($this->seq);
		unset($this->in_seq);
		unset($this->lcs);

		// Skip leading common lines.
		for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
			if ($from_lines[$skip] != $to_lines[$skip]) {
				break;
			}
			$this->xchanged[$skip] = $this->ychanged[$skip] = false;
		}

		// Skip trailing common lines.
		$xi = $n_from;
		$yi = $n_to;
		for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
			if ($from_lines[$xi] != $to_lines[$yi]) {
				break;
			}
			$this->xchanged[$xi] = $this->ychanged[$yi] = false;
		}

		// Ignore lines which do not exist in both files.
		for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
			$xhash[$from_lines[$xi]] = 1;
		}
		for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
			$line = $to_lines[$yi];
			if (($this->ychanged[$yi] = empty($xhash[$line]))) {
				continue;
			}
			$yhash[$line] = 1;
			$this->yv[] = $line;
			$this->yind[] = $yi;
		}
		for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
			$line = $from_lines[$xi];
			if (($this->xchanged[$xi] = empty($yhash[$line]))) {
				continue;
			}
			$this->xv[] = $line;
			$this->xind[] = $xi;
		}

		// Find the LCS.
		$this->_compareseq(0, count($this->xv), 0, count($this->yv));

		// Merge edits when possible.
		$this->_shiftBoundaries($from_lines, $this->xchanged, $this->ychanged);
		$this->_shiftBoundaries($to_lines, $this->ychanged, $this->xchanged);

		// Compute the edit operations.
		$edits = [];
		$xi = $yi = 0;
		while ($xi < $n_from || $yi < $n_to) {
//            assert($yi < $n_to || $this->xchanged[$xi]);
//            assert($xi < $n_from || $this->ychanged[$yi]);

			// Skip matching "snake".
			$copy = [];
			while ($xi < $n_from && $yi < $n_to
				   && ! $this->xchanged[$xi] && ! $this->ychanged[$yi]) {
				$copy[] = $from_lines[$xi++];
				++$yi;
			}
			if ($copy) {
				$edits[] = new Text_Diff_Op_copy($copy);
			}

			// Find deletes & adds.
			$delete = [];
			while ($xi < $n_from && $this->xchanged[$xi]) {
				$delete[] = $from_lines[$xi++];
			}

			$add = [];
			while ($yi < $n_to && $this->ychanged[$yi]) {
				$add[] = $to_lines[$yi++];
			}

			if ($delete && $add) {
				$edits[] = new Text_Diff_Op_change($delete, $add);
			} elseif ($delete) {
				$edits[] = new Text_Diff_Op_delete($delete);
			} elseif ($add) {
				$edits[] = new Text_Diff_Op_add($add);
			}
		}

		return $edits;
	}

	/**
	 * Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
	 * XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized
	 * segments.
	 *
	 * Returns (LCS, PTS).  LCS is the length of the LCS. PTS is an array of
	 * NCHUNKS+1 (X, Y) indexes giving the diving points between sub
	 * sequences.  The first sub-sequence is contained in (X0, X1), (Y0, Y1),
	 * the second in (X1, X2), (Y1, Y2) and so on.  Note that (X0, Y0) ==
	 * (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
	 *
	 * This function assumes that the first lines of the specified portions of
	 * the two files do not match, and likewise that the last lines do not
	 * match.  The caller must trim matching lines from the beginning and end
	 * of the portions it is going to specify.
	 */
	function _diag($xoff, $xlim, $yoff, $ylim, $nchunks)
	{
		$flip = false;

		if ($xlim - $xoff > $ylim - $yoff) {
			/* Things seems faster (I'm not sure I understand why) when the
			 * shortest sequence is in X. */
			$flip = true;
			list ($xoff, $xlim, $yoff, $ylim)
				= [$yoff, $ylim, $xoff, $xlim];
		}

		if ($flip) {
			for ($i = $ylim - 1; $i >= $yoff; $i--) {
				$ymatches[$this->xv[$i]][] = $i;
			}
		} else {
			for ($i = $ylim - 1; $i >= $yoff; $i--) {
				$ymatches[$this->yv[$i]][] = $i;
			}
		}

		$this->lcs = 0;
		$this->seq[0] = $yoff - 1;
		$this->in_seq = [];
		$ymids[0] = [];

		$numer = $xlim - $xoff + $nchunks - 1;
		$x = $xoff;
		for ($chunk = 0; $chunk < $nchunks; $chunk++) {
			if ($chunk > 0) {
				for ($i = 0; $i <= $this->lcs; $i++) {
					$ymids[$i][$chunk - 1] = $this->seq[$i];
				}
			}

			$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $chunk) / $nchunks);
			for (; $x < $x1; $x++) {
				$line = $flip ? $this->yv[$x] : $this->xv[$x];
				if (empty($ymatches[$line])) {
					continue;
				}
				$matches = $ymatches[$line];
				foreach ($matches as $y) {
					if (empty($this->in_seq[$y])) {
						$k = $this->_lcsPos($y);
//                        assert($k > 0);
						$ymids[$k] = $ymids[$k - 1];
						break;
					}
				}

				foreach ($matches as $y) {
					if ($y > $this->seq[$k - 1]) {
//                        assert($y < $this->seq[$k]);
						/* Optimization: this is a common case: next match is
						 * just replacing previous match. */
						$this->in_seq[$this->seq[$k]] = false;
						$this->seq[$k] = $y;
						$this->in_seq[$y] = 1;
					} elseif (empty($this->in_seq[$y])) {
						$k = $this->_lcsPos($y);
//                        assert($k > 0);
						$ymids[$k] = $ymids[$k - 1];
					}
				}
			}
		}

		$seps[] = $flip ? [$yoff, $xoff] : [$xoff, $yoff];
		$ymid = $ymids[$this->lcs];
		for ($n = 0; $n < $nchunks - 1; $n++) {
			$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
			$y1 = $ymid[$n] + 1;
			$seps[] = $flip ? [$y1, $x1] : [$x1, $y1];
		}
		$seps[] = $flip ? [$ylim, $xlim] : [$xlim, $ylim];

		return [$this->lcs, $seps];
	}

	function _lcsPos($ypos)
	{
		$end = $this->lcs;
		if ($end == 0 || $ypos > $this->seq[$end]) {
			$this->seq[++$this->lcs] = $ypos;
			$this->in_seq[$ypos] = 1;
			return $this->lcs;
		}

		$beg = 1;
		while ($beg < $end) {
			$mid = (int)(($beg + $end) / 2);
			if ($ypos > $this->seq[$mid]) {
				$beg = $mid + 1;
			} else {
				$end = $mid;
			}
		}

//        assert($ypos != $this->seq[$end]);

		$this->in_seq[$this->seq[$end]] = false;
		$this->seq[$end] = $ypos;
		$this->in_seq[$ypos] = 1;
		return $end;
	}

	/**
	 * Finds LCS of two sequences.
	 *
	 * The results are recorded in the vectors $this->{x,y}changed[], by
	 * storing a 1 in the element for each line that is an insertion or
	 * deletion (ie. is not in the LCS).
	 *
	 * The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
	 *
	 * Note that XLIM, YLIM are exclusive bounds.  All line numbers are
	 * origin-0 and discarded lines are not counted.
	 */
	function _compareseq($xoff, $xlim, $yoff, $ylim)
	{
		/* Slide down the bottom initial diagonal. */
		while ($xoff < $xlim && $yoff < $ylim
			   && $this->xv[$xoff] == $this->yv[$yoff]) {
			++$xoff;
			++$yoff;
		}

		/* Slide up the top initial diagonal. */
		while ($xlim > $xoff && $ylim > $yoff
			   && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
			--$xlim;
			--$ylim;
		}

		if ($xoff == $xlim || $yoff == $ylim) {
			$lcs = 0;
		} else {
			/* This is ad hoc but seems to work well.  $nchunks =
			 * sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5); $nchunks =
			 * max(2,min(8,(int)$nchunks)); */
			$nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
			list($lcs, $seps)
				= $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
		}

		if ($lcs == 0) {
			/* X and Y sequences have no common subsequence: mark all
			 * changed. */
			while ($yoff < $ylim) {
				$this->ychanged[$this->yind[$yoff++]] = 1;
			}
			while ($xoff < $xlim) {
				$this->xchanged[$this->xind[$xoff++]] = 1;
			}
		} else {
			/* Use the partitions to split this problem into subproblems. */
			reset($seps);
			$pt1 = $seps[0];
			while ($pt2 = next($seps)) {
				$this->_compareseq($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
				$pt1 = $pt2;
			}
		}
	}

	/**
	 * Adjusts inserts/deletes of identical lines to join changes as much as
	 * possible.
	 *
	 * We do something when a run of changed lines include a line at one end
	 * and has an excluded, identical line at the other.  We are free to
	 * choose which identical line is included.  `compareseq' usually chooses
	 * the one at the beginning, but usually it is cleaner to consider the
	 * following identical line to be the "change".
	 *
	 * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
	 */
	function _shiftBoundaries($lines, &$changed, $other_changed)
	{
		$i = 0;
		$j = 0;

//        assert('count($lines) == count($changed)');
		$len = count($lines);
		$other_len = count($other_changed);

		while (1) {
			/* Scan forward to find the beginning of another run of
			 * changes. Also keep track of the corresponding point in the
			 * other file.
			 *
			 * Throughout this code, $i and $j are adjusted together so that
			 * the first $i elements of $changed and the first $j elements of
			 * $other_changed both contain the same number of zeros (unchanged
			 * lines).
			 *
			 * Furthermore, $j is always kept so that $j == $other_len or
			 * $other_changed[$j] == false. */
			while ($j < $other_len && $other_changed[$j]) {
				$j++;
			}

			while ($i < $len && ! $changed[$i]) {
//                assert('$j < $other_len && ! $other_changed[$j]');
				$i++;
				$j++;
				while ($j < $other_len && $other_changed[$j]) {
					$j++;
				}
			}

			if ($i == $len) {
				break;
			}

			$start = $i;

			/* Find the end of this run of changes. */
			while (++$i < $len && $changed[$i]) {
				continue;
			}

			do {
				/* Record the length of this run of changes, so that we can
				 * later determine whether the run has grown. */
				$runlength = $i - $start;

				/* Move the changed region back, so long as the previous
				 * unchanged line matches the last changed one.  This merges
				 * with previous changed regions. */
				while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
					$changed[--$start] = 1;
					$changed[--$i] = false;
					while ($start > 0 && $changed[$start - 1]) {
						$start--;
					}
//                    assert('$j > 0');
					while ($other_changed[--$j]) {
						continue;
					}
//                    assert('$j >= 0 && !$other_changed[$j]');
				}

				/* Set CORRESPONDING to the end of the changed run, at the
				 * last point where it corresponds to a changed run in the
				 * other file. CORRESPONDING == LEN means no such point has
				 * been found. */
				$corresponding = $j < $other_len ? $i : $len;

				/* Move the changed region forward, so long as the first
				 * changed line matches the following unchanged one.  This
				 * merges with following changed regions.  Do this second, so
				 * that if there are no merges, the changed region is moved
				 * forward as far as possible. */
				while ($i < $len && $lines[$start] == $lines[$i]) {
					$changed[$start++] = false;
					$changed[$i++] = 1;
					while ($i < $len && $changed[$i]) {
						$i++;
					}

//                    assert('$j < $other_len && ! $other_changed[$j]');
					$j++;
					if ($j < $other_len && $other_changed[$j]) {
						$corresponding = $i;
						while ($j < $other_len && $other_changed[$j]) {
							$j++;
						}
					}
				}
			} while ($runlength != $i - $start);

			/* If possible, move the fully-merged run of changes back to a
			 * corresponding run in the other file. */
			while ($corresponding < $i) {
				$changed[--$start] = 1;
				$changed[--$i] = 0;
//                assert('$j > 0');
				while ($other_changed[--$j]) {
					continue;
				}
//                assert('$j >= 0 && !$other_changed[$j]');
			}
		}
	}
}

/**
 * @package Text_Diff
 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
 * @access  private
 */
class Text_Diff_Op
{
	var $orig;
	var $final;

	function reverse()
	{
		trigger_error('Abstract method', E_USER_ERROR);
	}

	function norig()
	{
		return $this->orig ? count($this->orig) : 0;
	}

	function nfinal()
	{
		return $this->final ? count($this->final) : 0;
	}
}

/**
 * @package Text_Diff
 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
 * @access  private
 */
class Text_Diff_Op_copy extends Text_Diff_Op
{
	function __construct($orig, $final = false)
	{
		if (! is_array($final)) {
			$final = $orig;
		}
		$this->orig = $orig;
		$this->final = $final;
	}

	function &reverse()
	{
		return $reverse = new Text_Diff_Op_copy($this->final, $this->orig);
	}
}

/**
 * @package Text_Diff
 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
 * @access  private
 */
class Text_Diff_Op_delete extends Text_Diff_Op
{
	function __construct($lines)
	{
		$this->orig = $lines;
		$this->final = false;
	}

	function &reverse()
	{
		return $reverse = new Text_Diff_Op_add($this->orig);
	}
}

/**
 * @package Text_Diff
 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
 * @access  private
 */
class Text_Diff_Op_add extends Text_Diff_Op
{
	function __construct($lines)
	{
		$this->final = $lines;
		$this->orig = false;
	}

	function &reverse()
	{
		return $reverse = new Text_Diff_Op_delete($this->final);
	}
}

/**
 * @package Text_Diff
 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
 * @access  private
 */
class Text_Diff_Op_change extends Text_Diff_Op
{
	function __construct($orig, $final)
	{
		$this->orig = $orig;
		$this->final = $final;
	}

	function &reverse()
	{
		return $reverse = new Text_Diff_Op_change($this->final, $this->orig);
	}
}
