Method truncateComplex

/**
 * Method to extend the truncate method to more complex situations
 *
 * The goal is to get the proper length plain text string with as much of
 * the html intact as possible with all tags properly closed.
 *
 * @param   string   $html       The content of the introtext to be truncated
 * @param   integer  $maxLength  The maximum number of characters to render
 * @param   boolean  $noSplit    Don't split a word if that is where the cutoff occurs (default: true).
 *
 * @return  string  The truncated string. If the string is truncated an ellipsis
 *                  (...) will be appended.
 *
 * @note    If a maximum length of 3 or less is selected and the text has more than
 *          that number of characters an ellipsis will be displayed.
 *          This method will not create valid HTML from malformed HTML.
 *
 * @since   3.1
 */
public static function truncateComplex($html, $maxLength = 0, $noSplit = true)
{
    // Start with some basic rules.
    $baseLength = strlen($html);
    // If the original HTML string is shorter than the $maxLength do nothing and return that.
    if ($baseLength <= $maxLength || $maxLength === 0) {
        return $html;
    }
    // Take care of short simple cases.
    if ($maxLength <= 3 && $html[0] !== '<' && strpos(substr($html, 0, $maxLength - 1), '<') === false && $baseLength > $maxLength) {
        return '...';
    }
    // Deal with maximum length of 1 where the string starts with a tag.
    if ($maxLength === 1 && $html[0] === '<') {
        $endTagPos = strlen(strstr($html, '>', true));
        $tag = substr($html, 1, $endTagPos);
        $l = $endTagPos + 1;
        if ($noSplit) {
            return substr($html, 0, $l) . '</' . $tag . '...';
        }
        // @todo: $character doesn't seem to be used...
        $character = substr(strip_tags($html), 0, 1);
        return substr($html, 0, $l) . '</' . $tag . '...';
    }
    // First get the truncated plain text string. This is the rendered text we want to end up with.
    $ptString = HTMLHelper::_('string.truncate', $html, $maxLength, $noSplit, $allowHtml = false);
    // It's all HTML, just return it.
    if ($ptString === '') {
        return $html;
    }
    // If the plain text is shorter than the max length the variable will not end in ...
    // In that case we use the whole string.
    if (substr($ptString, -3) !== '...') {
        return $html;
    }
    // Regular truncate gives us the ellipsis but we want to go back for text and tags.
    if ($ptString === '...') {
        $stripped = substr(strip_tags($html), 0, $maxLength);
        $ptString = HTMLHelper::_('string.truncate', $stripped, $maxLength, $noSplit, $allowHtml = false);
    }
    // We need to trim the ellipsis that truncate adds.
    $ptString = rtrim($ptString, '.');
    // Now deal with more complex truncation.
    while ($maxLength <= $baseLength) {
        // Get the truncated string assuming HTML is allowed.
        $htmlString = HTMLHelper::_('string.truncate', $html, $maxLength, $noSplit, $allowHtml = true);
        if ($htmlString === '...' && strlen($ptString) + 3 > $maxLength) {
            return $htmlString;
        }
        $htmlString = rtrim($htmlString, '.');
        // Now get the plain text from the HTML string and trim it.
        $htmlStringToPtString = HTMLHelper::_('string.truncate', $htmlString, $maxLength, $noSplit, $allowHtml = false);
        $htmlStringToPtString = rtrim($htmlStringToPtString, '.');
        // If the new plain text string matches the original plain text string we are done.
        if ($ptString === $htmlStringToPtString) {
            return $htmlString . '...';
        }
        // Get the number of HTML tag characters in the first $maxLength characters
        $diffLength = strlen($ptString) - strlen($htmlStringToPtString);
        if ($diffLength <= 0) {
            return $htmlString . '...';
        }
        // Set new $maxlength that adjusts for the HTML tags
        $maxLength += $diffLength;
    }
}