<?php

/**

 * Parses unified or context diffs output from eg. the diff utility.

 *

 * Example:

 * <code>

 * $patch = file_get_contents('example.patch');

 * $diff = &new Text_Diff('string', array($patch));

 * $renderer = &new Text_Diff_Renderer_inline();

 * echo $renderer->render($diff);

 * </code>

 *

 * @author    �rjan Persson <o@42mm.org>

 * @copyright Copyright 2005 �rjan Persson

 * @package   Text_Diff

 * @since     0.2.0

 * @access    private

 */

class Text_Diff_Engine_string {

    /**

     * Parses a unified or context diff.

     *

     * First param contains the whole diff and the second can be used to force 

     * a specific diff type. If the second parameter is 'autodetect', the 

     * diff will be examined to find out which type of diff this is.

     * 

     * @param string $diff  The diff content.

     * @param string $mode  The diff mode of the content in $diff. One of

     *                      'context', 'unified', or 'autodetect'.

     *

     * @return array  List of all diff operations.

     */

    function diff($diff, $mode = 'autodetect')

    {

        if ($mode != 'autodetect' && $mode != 'context' && $mode != 'unified') {

            die_friendly('Text_Diff', '<p>Type of diff is unsupported</p>');

        }

        if ($mode == 'autodetect') {

            $context = strpos($diff, '***');

            $unified = strpos($diff, '---');

            if ($context === $unified) {

                die_friendly('Text_Diff', '<p>Type of diff could not be detected</p>');

            } elseif ($context === false || $context === false) {

                $mode = $context !== false ? 'context' : 'unified';

            } else {

                $mode = $context < $unified ? 'context' : 'unified';

            }

        }

        // split by new line and remove the diff header

        $diff = explode("\n", $diff);

        array_shift($diff);

        array_shift($diff);

        if ($mode == 'context') {

            return $this->parseContextDiff($diff);

        } else {

            return $this->parseUnifiedDiff($diff);

        }

    }

    /**

     * Parses an array containing the unified diff.

     *

     * @param array $diff  Array of lines.

     *

     * @return array  List of all diff operations.

     */

    function parseUnifiedDiff($diff)

    {

        $edits = array();

        $end = count($diff) - 1;

        for ($i = 0; $i < $end;) {

            $diff1 = array();

            switch (substr($diff[$i], 0, 1)) {

            case ' ':

                do {

                    $diff1[] = substr($diff[$i], 1);

                } while (++$i < $end && substr($diff[$i], 0, 1) == ' ');

                $edits[] = &new Text_Diff_Op_copy($diff1);

                break;

            case '+':

                // get all new lines

                do {

                    $diff1[] = substr($diff[$i], 1);

                } while (++$i < $end && substr($diff[$i], 0, 1) == '+');

                $edits[] = &new Text_Diff_Op_add($diff1);

                break;

            case '-':

                // get changed or removed lines

                $diff2 = array();

                do {

                    $diff1[] = substr($diff[$i], 1);

                } while (++$i < $end && substr($diff[$i], 0, 1) == '-');

                while ($i < $end && substr($diff[$i], 0, 1) == '+') {

                    $diff2[] = substr($diff[$i++], 1);

                }

                if (count($diff2) == 0) {

                    $edits[] = &new Text_Diff_Op_delete($diff1);

                } else {

                    $edits[] = &new Text_Diff_Op_change($diff1, $diff2);

                }

                break;

            default:

                $i++;

                break;

            }

        }

        return $edits;

    }

    /**

     * Parses an array containing the context diff.

     *

     * @param array $diff  Array of lines.

     *

     * @return array  List of all diff operations.

     */

    function parseContextDiff(&$diff)

    {

        $edits = array();

        $i = $max_i = $j = $max_j = 0;

        $end = count($diff) - 1;

        while ($i < $end && $j < $end) {

            while ($i >= $max_i && $j >= $max_j) {

                // find the boundaries of the diff output of the two files

                for ($i = $j;

                     $i < $end && substr($diff[$i], 0, 3) == '***';

                     $i++);

                for ($max_i = $i;

                     $max_i < $end && substr($diff[$max_i], 0, 3) != '---';

                     $max_i++);

                for ($j = $max_i;

                     $j < $end && substr($diff[$j], 0, 3) == '---';

                     $j++);

                for ($max_j = $j;

                     $max_j < $end && substr($diff[$max_j], 0, 3) != '***';

                     $max_j++);

            }

            // find what hasn't been changed

            $array = array();

            while ($i < $max_i &&

                   $j < $max_j &&

                   strcmp($diff[$i], $diff[$j]) == 0) {

                $array[] = substr($diff[$i], 2);

                $i++;

                $j++;

            }

            while ($i < $max_i && ($max_j-$j) <= 1) {

                if ($diff[$i] != '' && substr($diff[$i], 0, 1) != ' ') {

                    break;

                }

                $array[] = substr($diff[$i++], 2);

            }

            while ($j < $max_j && ($max_i-$i) <= 1) {

                if ($diff[$j] != '' && substr($diff[$j], 0, 1) != ' ') {

                    break;

                }

                $array[] = substr($diff[$j++], 2);

            }

            if (count($array) > 0) {

                $edits[] = &new Text_Diff_Op_copy($array);

            }

            if ($i < $max_i) {

                $diff1 = array();

                switch (substr($diff[$i], 0, 1)) {

                case '!':

                    $diff2 = array();

                    do {

                        $diff1[] = substr($diff[$i], 2);

                        if ($j < $max_j && substr($diff[$j], 0, 1) == '!') {

                            $diff2[] = substr($diff[$j++], 2);

                        }

                    } while (++$i < $max_i && substr($diff[$i], 0, 1) == '!');

                    $edits[] = &new Text_Diff_Op_change($diff1, $diff2);

                    break;

                case '+':

                    do {

                        $diff1[] = substr($diff[$i], 2);

                    } while (++$i < $max_i && substr($diff[$i], 0, 1) == '+');

                    $edits[] = &new Text_Diff_Op_add($diff1);

                    break;

                case '-':

                    do {

                        $diff1[] = substr($diff[$i], 2);

                    } while (++$i < $max_i && substr($diff[$i], 0, 1) == '-');

                    $edits[] = &new Text_Diff_Op_delete($diff1);

                    break;

                }

            }

            if ($j < $max_j) {

                $diff2 = array();

                switch (substr($diff[$j], 0, 1)) {

                case '+':

                    do {

                        $diff2[] = substr($diff[$j++], 2);

                    } while ($j < $max_j && substr($diff[$j], 0, 1) == '+');

                    $edits[] = &new Text_Diff_Op_add($diff2);

                    break;

                case '-':

                    do {

                        $diff2[] = substr($diff[$j++], 2);

                    } while ($j < $max_j && substr($diff[$j], 0, 1) == '-');

                    $edits[] = &new Text_Diff_Op_delete($diff2);

                    break;

                }

            }

        }

        return $edits;

    }

}