/**
 * Truncates HTML text retaining tags and formatting. 
 * See http://www.pjgalbraith.com/2011/11/truncating-text-html-with-php/ for related blog post.
 *
 * Example:
 *
 * $output = TruncateHTML::truncateChars($your_html, '40', '...');
 * $output = TruncateHTML::truncateWords($your_html, '7', '...');
 *
 * @author pjgalbraith http://www.pjgalbraith.com
 *
 */

/*
    Copyright (c) 2011 Patrick Galbraith (http://www.pjgalbraith.com).
    All rights reserved.
    
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:
    
    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.
    
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    THE SOFTWARE.
*/

class TruncateHTML {
    
    public static function truncateChars($html, $limit, $ellipsis = '...') {
        
        if($limit <= 0 || $limit >= strlen(strip_tags($html)))
            return $html;
        
        $dom = new DOMDocument();
        $dom->loadHTML($html);
        
        $body = $dom->getElementsByTagName("body")->item(0);
        
        $it = new DOMLettersIterator($body);
        
        foreach($it as $letter) {
            if($it->key() >= $limit) {
                $currentText = $it->currentTextPosition();
                $currentText[0]->nodeValue = substr($currentText[0]->nodeValue, 0, $currentText[1] + 1);
                self::removeProceedingNodes($currentText[0], $body);
                self::insertEllipsis($currentText[0], $ellipsis);
                break;
            }
        }
        
        return preg_replace('~<(?:!DOCTYPE|/?(?:html|head|body))[^>]*>\s*~i', '', $dom->saveHTML());
    }
    
    public static function truncateWords($html, $limit, $ellipsis = '...') {
        
        if($limit <= 0 || $limit >= self::countWords(strip_tags($html)))
            return $html;
        
        $dom = new DOMDocument();
        $dom->loadHTML($html);
        
        $body = $dom->getElementsByTagName("body")->item(0);
        
        $it = new DOMWordsIterator($body);
        
        foreach($it as $word) {            
            if($it->key() >= $limit) {
                $currentWordPosition = $it->currentWordPosition();
                $curNode = $currentWordPosition[0];
                $offset = $currentWordPosition[1];
                $words = $currentWordPosition[2];
                
                $curNode->nodeValue = substr($curNode->nodeValue, 0, $words[$offset][1] + strlen($words[$offset][0]));
                
                self::removeProceedingNodes($curNode, $body);
                self::insertEllipsis($curNode, $ellipsis);
                break;
            }
        }
        
        return preg_replace('~<(?:!DOCTYPE|/?(?:html|head|body))[^>]*>\s*~i', '', $dom->saveHTML());
    }
    
    private static function removeProceedingNodes(DOMNode $domNode, DOMNode $topNode) {        
        $nextNode = $domNode->nextSibling;
        
        if($nextNode !== NULL) {
            self::removeProceedingNodes($nextNode, $topNode);
            $domNode->parentNode->removeChild($nextNode);
        } else {
            //scan upwards till we find a sibling
            $curNode = $domNode->parentNode;
            while($curNode !== $topNode) {
                if($curNode->nextSibling !== NULL) {
                    $curNode = $curNode->nextSibling;
                    self::removeProceedingNodes($curNode, $topNode);
                    $curNode->parentNode->removeChild($curNode);
                    break;
                }
                $curNode = $curNode->parentNode;
            }
        }
    }
    
    private static function insertEllipsis(DOMNode $domNode, $ellipsis) {    
        $avoid = array('a', 'strong', 'em', 'h1', 'h2', 'h3', 'h4', 'h5'); //html tags to avoid appending the ellipsis to
        
        if( in_array($domNode->parentNode->nodeName, $avoid) && $domNode->parentNode->parentNode !== NULL) {
            // Append as text node to parent instead
            $textNode = new DOMText($ellipsis);
            
            if($domNode->parentNode->parentNode->nextSibling)
                $domNode->parentNode->parentNode->insertBefore($textNode, $domNode->parentNode->parentNode->nextSibling);
            else
                $domNode->parentNode->parentNode->appendChild($textNode);
        } else {
            // Append to current node
            $domNode->nodeValue = rtrim($domNode->nodeValue).$ellipsis;
        }
    }
    
    private static function countWords($text) {
        $words = preg_split("/[\n\r\t ]+/", $text, -1, PREG_SPLIT_NO_EMPTY);
        return count($words);
    }
    
}