<?php

/**

 * Class used internally by Diff to actually compute the diffs.

 *

 * This class uses the Unix `diff` program via shell_exec to compute the

 * differences between the two input arrays.

 *

 * Copyright 2007-2010 The Horde Project (http://www.horde.org/)

 *

 * See the enclosed file COPYING for license information (LGPL). If you did

 * not receive this file, see http://opensource.org/licenses/lgpl-license.php.

 *

 * @author  Milian Wolff <mail@milianw.de>

 * @package Text_Diff

 * @since   0.3.0

 */

class Text_Diff_Engine_shell {

    /**

     * Path to the diff executable

     *

     * @var string

     */

    var $_diffCommand = 'diff';

    /**

     * Returns the array of differences.

     *

     * @param array $from_lines lines of text from old file

     * @param array $to_lines   lines of text from new file

     *

     * @return array all changes made (array with Text_Diff_Op_* objects)

     */

    function diff($from_lines, $to_lines)

    {

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

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

        $temp_dir = Text_Diff::_getTempDir();

        // Execute gnu diff or similar to get a standard diff file.

        $from_file = tempnam($temp_dir, 'Text_Diff');

        $to_file = tempnam($temp_dir, 'Text_Diff');

        $fp = fopen($from_file, 'w');

        fwrite($fp, implode("\n", $from_lines));

        fclose($fp);

        $fp = fopen($to_file, 'w');

        fwrite($fp, implode("\n", $to_lines));

        fclose($fp);

        $diff = shell_exec($this->_diffCommand . ' ' . $from_file . ' ' . $to_file);

        unlink($from_file);

        unlink($to_file);

        if (is_null($diff)) {

            // No changes were made

            return array(new Text_Diff_Op_copy($from_lines));

        }

        $from_line_no = 1;

        $to_line_no = 1;

        $edits = array();

        // Get changed lines by parsing something like:

        // 0a1,2

        // 1,2c4,6

        // 1,5d6

        preg_match_all('#^(\d+)(?:,(\d+))?([adc])(\d+)(?:,(\d+))?$#m', $diff,

            $matches, PREG_SET_ORDER);

        foreach ($matches as $match) {

            if (!isset($match[5])) {

                // This paren is not set every time (see regex).

                $match[5] = false;

            }

            if ($match[3] == 'a') {

                $from_line_no--;

            }

            if ($match[3] == 'd') {

                $to_line_no--;

            }

            if ($from_line_no < $match[1] || $to_line_no < $match[4]) {

                // copied lines

                assert('$match[1] - $from_line_no == $match[4] - $to_line_no');

                array_push($edits,

                    new Text_Diff_Op_copy(

                        $this->_getLines($from_lines, $from_line_no, $match[1] - 1),

                        $this->_getLines($to_lines, $to_line_no, $match[4] - 1)));

            }

            switch ($match[3]) {

            case 'd':

                // deleted lines

                array_push($edits,

                    new Text_Diff_Op_delete(

                        $this->_getLines($from_lines, $from_line_no, $match[2])));

                $to_line_no++;

                break;

            case 'c':

                // changed lines

                array_push($edits,

                    new Text_Diff_Op_change(

                        $this->_getLines($from_lines, $from_line_no, $match[2]),

                        $this->_getLines($to_lines, $to_line_no, $match[5])));

                break;

            case 'a':

                // added lines

                array_push($edits,

                    new Text_Diff_Op_add(

                        $this->_getLines($to_lines, $to_line_no, $match[5])));

                $from_line_no++;

                break;

            }

        }

        if (!empty($from_lines)) {

            // Some lines might still be pending. Add them as copied

            array_push($edits,

                new Text_Diff_Op_copy(

                    $this->_getLines($from_lines, $from_line_no,

                                     $from_line_no + count($from_lines) - 1),

                    $this->_getLines($to_lines, $to_line_no,

                                     $to_line_no + count($to_lines) - 1)));

        }

        return $edits;

    }

    /**

     * Get lines from either the old or new text

     *

     * @access private

     *

     * @param array &$text_lines Either $from_lines or $to_lines

     * @param int   &$line_no    Current line number

     * @param int   $end         Optional end line, when we want to chop more

     *                           than one line.

     *

     * @return array The chopped lines

     */

    function _getLines(&$text_lines, &$line_no, $end = false)

    {

        if (!empty($end)) {

            $lines = array();

            // We can shift even more

            while ($line_no <= $end) {

                array_push($lines, array_shift($text_lines));

                $line_no++;

            }

        } else {

            $lines = array(array_shift($text_lines));

            $line_no++;

        }

        return $lines;

    }

}