<?php
/**
 * Base renderer for rendering HTML based diffs for PHP DiffLib.
 *
 * PHP version 5
 *
 * Copyright (c) 2009 Chris Boulton <chris.boulton@interspire.com>
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 *  - Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *  - Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *  - Neither the name of the Chris Boulton nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * @package DiffLib
 * @author Chris Boulton <chris.boulton@interspire.com>
 * @copyright (c) 2009 Chris Boulton
 * @license New BSD License http://www.opensource.org/licenses/bsd-license.php
 * @version 1.1
 * @link http://github.com/chrisboulton/php-diff
 */

require_once dirname(__FILE__).'/../Abstract.php';

class Diff_Renderer_Html_Array extends Diff_Renderer_Abstract
{
	/**
	 * @var array Array of the default options that apply to this renderer.
	 */
	protected $defaultOptions = array(
		'tabSize' => 4
	);

	/**
	 * Render and return an array structure suitable for generating HTML
	 * based differences. Generally called by subclasses that generate a
	 * HTML based diff and return an array of the changes to show in the diff.
	 *
	 * @return array An array of the generated chances, suitable for presentation in HTML.
	 */
	public function render()
	{
		// As we'll be modifying a & b to include our change markers,
		// we need to get the contents and store them here. That way
		// we're not going to destroy the original data
		$a = $this->diff->getA();
		$b = $this->diff->getB();

		$changes = array();
		$opCodes = $this->diff->getGroupedOpcodes();
		foreach($opCodes as $group) {
			$blocks = array();
			$lastTag = null;
			$lastBlock = 0;
			foreach($group as $code) {
				list($tag, $i1, $i2, $j1, $j2) = $code;

				if($tag == 'replace' && $i2 - $i1 == $j2 - $j1) {
					for($i = 0; $i < ($i2 - $i1); ++$i) {
						$fromLine = $a[$i1 + $i];
						$toLine = $b[$j1 + $i];

						list($start, $end) = $this->getChangeExtent($fromLine, $toLine);
						if($start != 0 || $end != 0) {
							$last = $end + strlen($fromLine);
							$fromLine = substr_replace($fromLine, "\0", $start, 0);
							$fromLine = substr_replace($fromLine, "\1", $last + 1, 0);
							$last = $end + strlen($toLine);
							$toLine = substr_replace($toLine, "\0", $start, 0);
							$toLine = substr_replace($toLine, "\1", $last + 1, 0);
							$a[$i1 + $i] = $fromLine;
							$b[$j1 + $i] = $toLine;
						}
					}
				}

				if($tag != $lastTag) {
					$blocks[] = array(
						'tag' => $tag,
						'base' => array(
							'offset' => $i1,
							'lines' => array()
						),
						'changed' => array(
							'offset' => $j1,
							'lines' => array()
						)
					);
					$lastBlock = count($blocks)-1;
				}

				$lastTag = $tag;

				if($tag == 'equal') {
					$lines = array_slice($a, $i1, ($i2 - $i1));
					$blocks[$lastBlock]['base']['lines'] += $this->formatLines($lines);
					$lines = array_slice($b, $j1, ($j2 - $j1));
					$blocks[$lastBlock]['changed']['lines'] +=  $this->formatLines($lines);
				}
				else {
					if($tag == 'replace' || $tag == 'delete') {
						$lines = array_slice($a, $i1, ($i2 - $i1));
						$lines = $this->formatLines($lines);
						$lines = str_replace(array("\0", "\1"), array('<del>', '</del>'), $lines);
						$blocks[$lastBlock]['base']['lines'] += $lines;
					}

					if($tag == 'replace' || $tag == 'insert') {
						$lines = array_slice($b, $j1, ($j2 - $j1));
						$lines =  $this->formatLines($lines);
						$lines = str_replace(array("\0", "\1"), array('<ins>', '</ins>'), $lines);
						$blocks[$lastBlock]['changed']['lines'] += $lines;
					}
				}
			}
			$changes[] = $blocks;
		}
		return $changes;
	}

	/**
	 * Given two strings, determine where the changes in the two strings
	 * begin, and where the changes in the two strings end.
	 *
	 * @param string $fromLine The first string.
	 * @param string $toLine The second string.
	 * @return array Array containing the starting position (0 by default) and the ending position (-1 by default)
	 */
	private function getChangeExtent($fromLine, $toLine)
	{
		$start = 0;
		$limit = min(strlen($fromLine), strlen($toLine));
		while ($start < $limit && $fromLine[$start] == $toLine[$start]) {
			++$start;
		}
		$end = -1;
		$limit = $limit - $start;
		while(-$end <= $limit && substr($fromLine, $end, 1) == substr($toLine, $end, 1)) {
			--$end;
		}
		return array(
			$start,
			$end + 1
		);
	}

	/**
	 * Format a series of lines suitable for output in a HTML rendered diff.
	 * This involves replacing tab characters with spaces, making the HTML safe
	 * for output, ensuring that double spaces are replaced with &nbsp; etc.
	 *
	 * @param array $lines Array of lines to format.
	 * @return array Array of the formatted lines.
	 */
	protected function formatLines($lines)
	{
		$lines = array_map(array($this, 'ExpandTabs'), $lines);
		$lines = array_map(array($this, 'HtmlSafe'), $lines);
		foreach($lines as &$line) {
			$line = preg_replace_callback('# ( +)|^ #', array($this, 'fixSpaces'), $line);
		}
		return $lines;
	}

	/**
	 * Replace a string containing spaces with a HTML representation using &nbsp;.
	 *
	 * @param string[] $matches Array with preg matches.
	 * @return string The HTML representation of the string.
	 */
	private function fixSpaces(array $matches)
	{
		$spaces = $matches[1];
		$count = strlen($spaces);
		if($count == 0) {
			return '';
		}

		$div = floor($count / 2);
		$mod = $count % 2;
		return str_repeat('&nbsp; ', $div).str_repeat('&nbsp;', $mod);
	}

	/**
	 * Replace tabs in a single line with a number of spaces as defined by the tabSize option.
	 *
	 * @param string $line The containing tabs to convert.
	 * @return string The line with the tabs converted to spaces.
	 */
	private function expandTabs($line)
	{
		return str_replace("\t", str_repeat(' ', $this->options['tabSize']), $line);
	}

	/**
	 * Make a string containing HTML safe for output on a page.
	 *
	 * @param string $string The string.
	 * @return string The string with the HTML characters replaced by entities.
	 */
	private function htmlSafe($string)
	{
		return htmlspecialchars($string, ENT_NOQUOTES, 'UTF-8');
	}
}
