path: root/include/markdown.php

<?php
/**
 * @file include/markdown.php
 * @brief Some functions for BB conversions for Diaspora protocol.
 */

use Michelf\MarkdownExtra;

use League\HTMLToMarkdown\HtmlConverter;
use League\HTMLToMarkdown\Environment;
use League\HTMLToMarkdown\Converter\ConverterInterface;
use League\HTMLToMarkdown\ElementInterface;

require_once("include/oembed.php");
require_once("include/event.php");
require_once("include/html2bbcode.php");
require_once("include/bbcode.php");


/**
 * @brief Convert Markdown to bbcode.
 *
 * We don't want to support a bbcode specific markdown interpreter
 * and the markdown library we have is pretty good, but provides HTML output.
 * So we'll use that to convert to HTML, then convert the HTML back to bbcode,
 * and then clean up a few Diaspora specific constructs.
 *
 * @param string $s The message as Markdown
 * @param boolean $use_zrl default false
 * @param array $options default empty
 * @return string The message converted to bbcode
 */
function markdown_to_bb($s, $use_zrl = false, $options = []) {

	if(is_array($s)) {
		btlogger('markdown_to_bb called with array. ' . print_r($s, true), LOGGER_NORMAL, LOG_WARNING);
		return '';
	}

	$s = str_replace("&#xD;","\r",$s);
	$s = str_replace("&#xD;\n&gt;","",$s);

	$s = html_entity_decode($s,ENT_COMPAT,'UTF-8');

	// if empty link text replace with the url
	$s = preg_replace("/\[\]\((.*?)\)/ism",'[$1]($1)',$s);

	$x = [
			'text' => $s,
			'zrl' => $use_zrl,
			'options' => $options
	];
	/**
	 * @hooks markdown_to_bb_init
	 *   * \e string \b text - The message as Markdown and what will get returned
	 *   * \e boolean \b zrl
	 *   * \e array \b options
	 */
	call_hooks('markdown_to_bb_init', $x);

	$s = $x['text'];

	// Escaping the hash tags
	$s = preg_replace('/\#([^\s\#])/','&#35;$1',$s);

	$s = MarkdownExtra::defaultTransform($s);

	if($options && $options['preserve_lf']) {
		$s = str_replace(["\r","\n"],["",'<br>'],$s);
	}
	else {
		$s = str_replace("\r","",$s);
	}

	$s = str_replace('&#35;','#',$s);

	$s = html2bbcode($s);

	// Convert everything that looks like a link to a link
	if($use_zrl) {
		if (strpos($s,'[/img]') !== false) {
			$s = preg_replace_callback("/\[img\](.*?)\[\/img\]/ism", 'use_zrl_cb_img', $s);
			$s = preg_replace_callback("/\[img\=([0-9]*)x([0-9]*)\](.*?)\[\/img\]/ism", 'use_zrl_cb_img_x', $s);
		}
		$s = preg_replace_callback("/([^\]\=\{\/]|^)(https?\:\/\/)([a-zA-Z0-9\pL\:\/\-\?\&\;\.\=\_\~\#\%\$\!\+\,\@\(\)]+)/ismu", 'use_zrl_cb_link',$s);
	}
	else {
		$s = preg_replace("/([^\]\=\{\/]|^)(https?\:\/\/)([a-zA-Z0-9\pL\:\/\-\?\&\;\.\=\_\~\#\%\$\!\+\,\@\(\)]+)/ismu", '$1[url=$2$3]$2$3[/url]',$s);
	}

	// remove duplicate adjacent code tags
	$s = preg_replace("/(\[code\])+(.*?)(\[\/code\])+/ism","[code]$2[/code]", $s);

	// Don't show link to full picture (until it is fixed)
	$s = scale_external_images($s, false);

	/**
	 * @hooks markdown_to_bb
	 *   * \e string - The already converted message as bbcode
	 */
	call_hooks('markdown_to_bb', $s);

	return $s;
}

function use_zrl_cb_link($match) {
	$res = '';
	$is_zid = is_matrix_url(trim($match[0]));

	if($is_zid)
		$res = $match[1] . '[zrl=' . $match[2] . $match[3] . ']' . $match[2] . $match[3] . '[/zrl]';
	else
		$res = $match[1] . '[url=' . $match[2] . $match[3] . ']' . $match[2] . $match[3] . '[/url]';

	return $res;
}

function use_zrl_cb_img($match) {
	$res = '';
	$is_zid = is_matrix_url(trim($match[1]));

	if($is_zid)
		$res = '[zmg]' . $match[1] . '[/zmg]';
	else
		$res = $match[0];

	return $res;
}

function use_zrl_cb_img_x($match) {
	$res = '';
	$is_zid = is_matrix_url(trim($match[3]));

	if($is_zid)
		$res = '[zmg=' . $match[1] . 'x' . $match[2] . ']' . $match[3] . '[/zmg]';
	else
		$res = $match[0];

	return $res;
}

/**
 * @brief
 *
 * @param array $match
 * @return string
 */
function bb_to_markdown_share($match) {

	$matches = array();
	$attributes = $match[1];

	$author = "";
	preg_match("/author='(.*?)'/ism", $attributes, $matches);
	if ($matches[1] != "")
		$author = urldecode($matches[1]);

	$link = "";
	preg_match("/link='(.*?)'/ism", $attributes, $matches);
	if ($matches[1] != "")
		$link = $matches[1];

	$avatar = "";
	preg_match("/avatar='(.*?)'/ism", $attributes, $matches);
	if ($matches[1] != "")
		$avatar = $matches[1];

	$profile = "";
	preg_match("/profile='(.*?)'/ism", $attributes, $matches);
	if ($matches[1] != "")
		$profile = $matches[1];

	$posted = "";
	preg_match("/posted='(.*?)'/ism", $attributes, $matches);
	if ($matches[1] != "")
		$posted = $matches[1];

	// message_id is never used, do we still need it?
	$message_id = "";
	preg_match("/message_id='(.*?)'/ism", $attributes, $matches);
	if ($matches[1] != "")
		$message_id = $matches[1];

	if(! $message_id) {
		preg_match("/guid='(.*?)'/ism", $attributes, $matches);
		if ($matches[1] != "")
			$message_id = $matches[1];
	}


	$reldate = datetime_convert('UTC', date_default_timezone_get(), $posted, 'r');

	$headline = '';

	if ($avatar != "")
		$headline .= '[url=' . zid($profile) . '][img]' . $avatar . '[/img][/url]';

	// Bob Smith wrote the following post 2 hours ago

	$fmt = sprintf( t('%1$s wrote the following %2$s %3$s'),
		'[url=' . zid($profile) . ']' . $author . '[/url]',
		'[url=' . zid($link) . ']' . t('post') . '[/url]',
		$reldate
	);

	$headline .= $fmt . "\n\n";

	$text = $headline . trim($match[2]);

	return $text;
}


/**
 * @brief Convert bbcode to Markdown.
 *
 * @param string $Text The message as bbcode
 * @param array $options default empty
 * @return string The message converted to Markdown
 */
function bb_to_markdown($Text, $options = []) {

	/*
	 * Transform #tags, strip off the [url] and replace spaces with underscore
	 */

	$Text = preg_replace_callback('/#\[([zu])rl\=(.*?)\](.*?)\[\/[(zu)]rl\]/i',
		create_function('$match', 'return \'#\'. str_replace(\' \', \'_\', $match[3]);'), $Text);

	$Text = preg_replace('/#\^\[([zu])rl\=(.*?)\](.*?)\[\/([zu])rl\]/i', '[$1rl=$2]$3[/$4rl]', $Text);

	// Converting images with size parameters to simple images. Markdown doesn't know it.
	$Text = preg_replace("/\[img\=([0-9]*)x([0-9]*)\](.*?)\[\/img\]/ism", '[img]$3[/img]', $Text);

	$Text = preg_replace_callback("/\[share(.*?)\](.*?)\[\/share\]/ism", 'bb_to_markdown_share', $Text);

	$x = [ 'bbcode' => $Text, 'options' => $options ];

	/**
	 * @hooks bb_to_markdown_bb
	 *   * \e string \b bbcode - The message as bbcode and what will get returned
	 *   * \e array \b options
	 */
	call_hooks('bb_to_markdown_bb', $x);

	$Text = $x['bbcode'];

	// Convert it to HTML - don't try oembed
	$Text = bbcode($Text, [ 'tryoembed' => false ]);

	// Now convert HTML to Markdown
	$Text = html2markdown($Text);

	//html2markdown adds backslashes infront of hashes after a new line. remove them
	$Text = str_replace("\n\#", "\n#", $Text);

	// If the text going into bbcode() has a plain URL in it, i.e.
	// with no [url] tags around it, it will come out of parseString()
	// looking like: <http://url.com>, which gets removed by strip_tags().
	// So take off the angle brackets of any such URL
	$Text = preg_replace("/<http(.*?)>/is", "http$1", $Text);

	// Remove empty zrl links
	$Text = preg_replace("/\[zrl\=\].*?\[\/zrl\]/is", "", $Text);

	$Text = trim($Text);

	/**
	 * @hooks bb_to_markdown
	 *   * \e string - The already converted message as bbcode and what will get returned
	 */
	call_hooks('bb_to_markdown', $Text);

	return $Text;
}


/**
 * @brief Convert a HTML text into Markdown.
 *
 * This function uses the library league/html-to-markdown for this task.
 *
 * If the HTML text can not get parsed it will return an empty string.
 *
 * @param string $html The HTML code to convert
 * @return string Markdown representation of the given HTML text, empty on error
 */
function html2markdown($html,$options = []) {
	$markdown = '';

	$internal_errors = libxml_use_internal_errors(true);

	$environment = new Environment($options);
	$environment->createDefaultEnvironment();
	$environment->addConverter(new TableConverter());
	$converter = new HtmlConverter($environment);

	try {
		$markdown = $converter->convert($html);
	} catch (InvalidArgumentException $e) {
		logger("Invalid HTML. HTMLToMarkdown library threw an exception.");
	}

	libxml_use_internal_errors($internal_errors);

	return $markdown;
}

// Tables are not an official part of the markdown specification.
// This interface was suggested as a workaround.
// author: Mark Hamstra
// https://github.com/Mark-H/Docs


class TableConverter implements ConverterInterface
{
    /**
     * @param ElementInterface $element
     *
     * @return string
     */
    public function convert(ElementInterface $element)
    {
        switch ($element->getTagName()) {
            case 'tr':
                $line = [];
                $i = 1;
                foreach ($element->getChildren() as $td) {
                    $i++;
                    $v = $td->getValue();
                    $v = trim($v);
                    if ($i % 2 === 0 || $v !== '') {
                        $line[] = $v;
                    }
                }
                return '| ' . implode(' | ', $line) . " |\n";
            case 'td':
            case 'th':
                return trim($element->getValue());
            case 'tbody':
                return trim($element->getValue());
            case 'thead':
                $headerLine = reset($element->getChildren())->getValue();
                $headers = explode(' | ', trim(trim($headerLine, "\n"), '|'));
                $hr = [];
                foreach ($headers as $td) {
                    $length = strlen(trim($td)) + 2;
                    $hr[] = str_repeat('-', $length > 3 ? $length : 3);
                }
                $hr = '|' . implode('|', $hr) . '|';
                return $headerLine . $hr . "\n";
            case 'table':
                $inner = $element->getValue();
                if (strpos($inner, '-----') === false) {
                    $inner = explode("\n", $inner);
                    $single = explode(' | ', trim($inner[0], '|'));
                    $hr = [];
                    foreach ($single as $td) {
                        $length = strlen(trim($td)) + 2;
                        $hr[] = str_repeat('-', $length > 3 ? $length : 3);
                    }
                    $hr = '|' . implode('|', $hr) . '|';
                    array_splice($inner, 1, 0, $hr);
                    $inner = implode("\n", $inner);
                }
                return trim($inner) . "\n\n";
        }
        return $element->getValue();
    }
    /**
     * @return string[]
     */
    public function getSupportedTags()
    {
        return array('table', 'tr', 'thead', 'td', 'tbody');
    }
}