<?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;

    }

}