<?php

/**

 * 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)

		{

				array_walk($from_lines, array('Text_Diff', 'trimNewlines'));

				array_walk($to_lines, array('Text_Diff', 'trimNewlines'));

				/* 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 = array();

				foreach ($diff as $line) {

						switch ($line[0]) {

						case ' ':

								$edits[] = &new Text_Diff_Op_copy(array(substr($line, 1)));

								break;

						case '+':

								$edits[] = &new Text_Diff_Op_add(array(substr($line, 1)));

								break;

						case '-':

								$edits[] = &new Text_Diff_Op_delete(array(substr($line, 1)));

								break;

						}

				}

				return $edits;

		}

}