<?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;

		}

}