qa-viewer-basic.php

<?php
/*
	Question2Answer by Gideon Greenspan and contributors
	http://www.question2answer.org/

	Description: Basic viewer module for displaying HTML or plain text


	This program is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public License
	as published by the Free Software Foundation; either version 2
	of the License, or (at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	More about this license: http://www.question2answer.org/license.php
*/

class qa_viewer_basic
{
	private $htmllineseparators;
	private $htmlparagraphseparators;


	public function load_module($localdir, $htmldir)
	{
		$this->htmllineseparators = 'br|option';
		$this->htmlparagraphseparators = 'address|applet|blockquote|center|cite|col|div|dd|dl|dt|embed|form|frame|frameset|h1|h2|h3|h4|h5|h6' .
			'|hr|iframe|input|li|marquee|ol|p|pre|samp|select|spacer|table|tbody|td|textarea|tfoot|th|thead|tr|ul';
	}

	public function calc_quality($content, $format)
	{
		if ($format == '' || $format == 'html')
			return 1.0;

		return 0.0001; // if there's nothing better this will give an error message for unknown formats
	}

	public function get_html($content, $format, $options)
	{
		if ($format == 'html') {
			$html = qa_sanitize_html($content, @$options['linksnewwindow'], false); // sanitize again for display, for extra safety, and due to new window setting

			if (isset($options['blockwordspreg'])) { // filtering out blocked words inline within HTML is pretty complex, e.g. p<b>oo</b>p must be caught
				require_once QA_INCLUDE_DIR . 'util/string.php';

				$html = preg_replace('/<\s*(' . $this->htmllineseparators . ')[^A-Za-z0-9]/i', "\n\\0", $html); // tags to single new line
				$html = preg_replace('/<\s*(' . $this->htmlparagraphseparators . ')[^A-Za-z0-9]/i', "\n\n\\0", $html); // tags to double new line

				preg_match_all('/<[^>]*>/', $html, $pregmatches, PREG_OFFSET_CAPTURE); // find tag positions and lengths
				$tagmatches = $pregmatches[0];
				$text = preg_replace('/<[^>]*>/', '', $html); // effectively strip_tags() but use same regexp as above to ensure consistency

				$blockmatches = qa_block_words_match_all($text, $options['blockwordspreg']); // search for blocked words within text

				$nexttagmatch = array_shift($tagmatches);
				$texttohtml = 0;
				$htmlshift = 0;

				foreach ($blockmatches as $textoffset => $textlength) {
					while (isset($nexttagmatch) && ($nexttagmatch[1] <= ($textoffset + $texttohtml))) { // keep text and html in sync
						$texttohtml += strlen($nexttagmatch[0]);
						$nexttagmatch = array_shift($tagmatches);
					}

					while (1) {
						$replacepart = $textlength;
						if (isset($nexttagmatch))
							$replacepart = min($replacepart, $nexttagmatch[1] - ($textoffset + $texttohtml)); // stop replacing early if we hit an HTML tag

						$replacelength = qa_strlen(substr($text, $textoffset, $replacepart)); // to work with multi-byte characters

						$html = substr_replace($html, str_repeat('*', $replacelength), $textoffset + $texttohtml + $htmlshift, $replacepart);
						$htmlshift += $replacelength - $replacepart; // HTML might have moved around if we replaced multi-byte characters

						if ($replacepart >= $textlength)
							break; // we have replaced everything expected, otherwise more left (due to hitting an HTML tag)

						$textlength -= $replacepart;
						$textoffset += $replacepart;
						$texttohtml += strlen($nexttagmatch[0]);
						$nexttagmatch = array_shift($tagmatches);
					}
				}
			}

			if (@$options['showurllinks']) { // we need to ensure here that we don't put new links inside existing ones
				require_once QA_INCLUDE_DIR . 'util/string.php';

				$htmlunlinkeds = array_reverse(preg_split('#<(a|code|pre)[^>]*>.*</(a|code|pre)\s*>#ims', $html, -1, PREG_SPLIT_OFFSET_CAPTURE)); // start from end so we substitute correctly

				foreach ($htmlunlinkeds as $htmlunlinked) { // and that we don't detect links inside HTML, e.g. <img src="http://...">
					$thishtmluntaggeds = array_reverse(preg_split('/<[^>]*>/', $htmlunlinked[0], -1, PREG_SPLIT_OFFSET_CAPTURE)); // again, start from end

					foreach ($thishtmluntaggeds as $thishtmluntagged) {
						$innerhtml = $thishtmluntagged[0];

						if (is_numeric(strpos($innerhtml, '://'))) { // quick test first
							$newhtml = qa_html_convert_urls($innerhtml, qa_opt('links_in_new_window'));

							$html = substr_replace($html, $newhtml, $htmlunlinked[1] + $thishtmluntagged[1], strlen($innerhtml));
						}
					}
				}
			}

		} elseif ($format == '') {
			if (isset($options['blockwordspreg'])) {
				require_once QA_INCLUDE_DIR . 'util/string.php';
				$content = qa_block_words_replace($content, $options['blockwordspreg']);
			}

			$html = qa_html($content, true);

			if (@$options['showurllinks']) {
				require_once QA_INCLUDE_DIR . 'app/format.php';
				$html = qa_html_convert_urls($html, qa_opt('links_in_new_window'));
			}

		} else
			$html = '[no viewer found for format: ' . qa_html($format) . ']'; // for unknown formats

		return $html;
	}

	public function get_text($content, $format, $options)
	{
		if ($format == 'html') {
			$text = strtr($content, "\n\r\t", '   '); // convert all white space in HTML to spaces
			$text = preg_replace('/<\s*(' . $this->htmllineseparators . ')[^A-Za-z0-9]/i', "\n\\0", $text); // tags to single new line
			$text = preg_replace('/<\s*(' . $this->htmlparagraphseparators . ')[^A-Za-z0-9]/i', "\n\n\\0", $text); // tags to double new line
			$text = strip_tags($text); // all tags removed
			$text = preg_replace('/  +/', ' ', $text); // combine multiple spaces into one
			$text = preg_replace('/ *\n */', "\n", $text); // remove spaces either side new lines
			$text = preg_replace('/\n\n\n+/', "\n\n", $text); // more than two new lines combine into two
			$text = strtr($text, array(
				'&#34;' => "\x22",
				'&#38;' => "\x26",
				'&#39;' => "\x27",
				'&#60;' => "\x3C",
				'&#62;' => "\x3E",
				'&nbsp;' => " ",
				'&quot;' => "\x22",
				'&amp;' => "\x26",
				'&lt;' => "\x3C",
				'&gt;' => "\x3E",
			)); // base HTML entities (others should not be stored in database)

			$text = trim($text);

		} elseif ($format == '')
			$text = $content;
		else
			$text = '[no viewer found for format: ' . $format . ']'; // for unknown formats

		if (isset($options['blockwordspreg'])) {
			require_once QA_INCLUDE_DIR . 'util/string.php';
			$text = qa_block_words_replace($text, $options['blockwordspreg']);
		}

		return $text;
	}
}