Fix long URL formatting causing bugnote/text to be blank

When MantisCoreFormatting plugin processes text (e.g. bugnote)
containing a long URL, a PREG_BACKTRACK_LIMIT_ERROR may occur in
string_insert_hrefs() when replacing email address links with
preg_replace_callback(). When pcre.backtrack_limit = 100000, the longest
URL that can be processed successfully is 152 chars. A bigger URL
triggers the PCRE error and the function returns NULL.

This was introduced by commit 21a3469.

We now use preg_split() instead of preg_replace_callback(), which is
more efficient and avoids the backtrace error issue

The url replacement string was also moved to a variable to make code
more readable.

Fixes #14447

core/string_api.php

@@ -446,7 +446,7 @@ function string_process_bugnote_link( $p_string, $p_include_anchor = true, $p_de
  */
 function string_insert_hrefs( $p_string ) {
 	static $s_url_regex = null;
-	static $s_email_regex = null;
+	static $s_anchor_regex = '/(<a[^>]*>.*?<\/a>)/is';
 
 	if( !config_get( 'html_make_links' ) ) {
 		return $p_string;
@@ -458,54 +458,50 @@ function string_insert_hrefs( $p_string ) {
 		ini_set( 'magic_quotes_sybase', false );
 	}
 
-	# Find any URL in a string and replace it by a clickable link
-	$t_url_protocol = '([[:alpha:]][-+.[:alnum:]]*):\/\/';
+	# Initialize URL regex static variable
 	if ( is_null( $s_url_regex ) ) {
+		$t_url_protocol = '(?:[[:alpha:]][-+.[:alnum:]]*):\/\/';
+
 		# %2A notation in url's
 		$t_url_hex = '%[[:digit:]A-Fa-f]{2}';
 
 		# valid set of characters that may occur in url scheme. Note: - should be first (A-F != -AF).
-		$t_url_valid_chars = '-_.,!~*\';\/?%^\\\\:@&={\|}+$#[:alnum:]\pL';
-
-		$t_url_chars = "(?:${t_url_hex}|[${t_url_valid_chars}\(\)\[\]])";
-		$t_url_chars2 = "(?:${t_url_hex}|[${t_url_valid_chars}])";
+		$t_url_valid_chars       = '-_.,!~*\';\/?%^\\\\:@&={\|}+$#[:alnum:]\pL';
+		$t_url_chars             = "(?:${t_url_hex}|[${t_url_valid_chars}\(\)\[\]])";
+		$t_url_chars2            = "(?:${t_url_hex}|[${t_url_valid_chars}])";
 		$t_url_chars_in_brackets = "(?:${t_url_hex}|[${t_url_valid_chars}\(\)])";
-		$t_url_chars_in_parens    = "(?:${t_url_hex}|[${t_url_valid_chars}\[\]])";
+		$t_url_chars_in_parens   = "(?:${t_url_hex}|[${t_url_valid_chars}\[\]])";
 
 		$t_url_part1 = "${t_url_chars}";
 		$t_url_part2 = "(?:\(${t_url_chars_in_parens}*\)|\[${t_url_chars_in_brackets}*\]|${t_url_chars2})";
 
 		$s_url_regex = "/(${t_url_protocol}(${t_url_part1}*?${t_url_part2}+))/sue";
 	}
 
+	# Find any URL in a string and replace it by a clickable link
 	$p_string = preg_replace( $s_url_regex, "'<a href=\"'.rtrim('\\1','.').'\">\\1</a> [<a href=\"'.rtrim('\\1','.').'\" target=\"_blank\">^</a>]'", $p_string );
 	if( $t_change_quotes ) {
 		ini_set( 'magic_quotes_sybase', true );
 	}
 
 	# Find any email addresses in the string and replace them with a clickable
-	# mailto: link, making sure that URLs such as http://user@example.com/ or
-	# http://user:password@example.com/ are not processed as an email
-	if( is_null( $s_email_regex ) ) {
-		$s_email_regex = email_regex_simple();
-		$s_email_regex =
-			substr( $s_email_regex, 0, 1 ) .
-			'(' . $t_url_protocol . '.*?)?' .
-			substr( $s_email_regex, 1 );
+	# mailto: link, making sure that we skip processing of any existing anchor
+	# tags, to avoid parts of URLs such as https://user@example.com/ or
+	# http://user:password@example.com/ to be not treated as an email.
+	$t_pieces = preg_split( $s_anchor_regex, $p_string, null, PREG_SPLIT_DELIM_CAPTURE );
+	$p_string = '';
+	foreach( $t_pieces as $piece ) {
+		if( preg_match( $s_anchor_regex, $piece ) ) {
+			$p_string .= $piece;
+		} else {
+			$p_string .= preg_replace(
+				email_regex_simple(),
+				'<a href="mailto:\0">\0</a>',
+				$piece
+			);
+		}
 	}
 
-	$p_string = preg_replace_callback(
-		$s_email_regex,
-		create_function(
-			'$p_match',
-			'if( 0 === preg_match( "/' . $t_url_protocol . '/", $p_match[0] ) ) {
-				return \'<a href="mailto:\' . $p_match[0] . \'">\' . $p_match[0] . \'</a>\';
-			} else {
-				return $p_match[0];
-			}'
-		),
-		$p_string );
-
 	return $p_string;
 }