<?php

/**
 * FPDF_Merge
 * Tool to merge PDFs created by fpdf 1.6         
 *  
 * @version 1.0
 * @date 2011-02-18
 * @author DEMONTE Jean-Baptiste <jbdemonte@gmail.com>
 * @copyright (C) Digitick <www.digitick.net> 2011
 * @license GNU Lesser General Public License v3.0
 * 
 * Why this tool ?
 *  
 * All the library tested (fpdi, ...) produce too heavy pdf
 * because, these are not optimized.
 * This library parses the pages, get the objects included (font, images)
 * generate a hash to store only once these objects or reuse previous stored ones.
 *  
 *    
 * Notes
 *  
 * - links are not supported in this version
 * - all pages are included (because this was what we needed) but update it 
 *   to create an add(array pages) should be easy 
 * 
 * 
 * I tried to optimize a lot this tool using X-Debug, let me know if you do best :)
 * If you get trouble or want to comment, feel free to send me an email.
 *
 * Use
 *  
 *  $merge = new FPDF_Merge();
 *  $merge->add('/tmp/pdf-1.pdf');
 *  $merge->add('/tmp/pdf-2.pdf');
 *  $merge->output('/tmp/pdf-merge.pdf'); // or $merge->output(); to open it directly in the browser
 *  
 * */
class FPDF_Merge {

    const TYPE_NULL = 0,
            TYPE_TOKEN = 1,
            TYPE_REFERENCE = 2,
            TYPE_REFERENCE_F = 3,
            TYPE_NUMERIC = 4,
            TYPE_HEX = 5,
            TYPE_BOOL = 6,
            TYPE_STRING = 7,
            TYPE_ARRAY = 8,
            TYPE_DICTIONARY = 9,
            TYPE_STREAM = 10;

    private $buffer, $compress, $fonts, $objects, $pages, $ref, $n, $xref;

    /*     * ************************************************
      /*                    CONSTRUCTOR
      /************************************************* */

    public function __construct() {
        $this->buffer = '';
        $this->fonts = array();
        $this->objects = array();
        $this->pages = array();
        $this->ref = array();
        $this->xref = array();
        $this->n = 0;
        $this->compress = function_exists('gzcompress');
    }

    /*     * ************************************************
      /*                      PRIVATE
      /************************************************* */

    private function error($msg) {
        throw new Exception($msg);
        die;
    }

    //================================================
    // FONCTIONS D'IMPORT
    //================================================

    private function parse($buffer, &$len, &$off) {
        if ($len === $off) {
            return null;
        }

        if (!preg_match('`\s*(.)`', $buffer, $m, PREG_OFFSET_CAPTURE, $off))
            return null;
        $off = $m[1][1];

        switch ($buffer[$off]) {
            case '<':
                if ($buffer[$off + 1] === '<') {
                    // dictionnary
                    $v = array();
                    $off+=2;
                    while (1) {
                        $key = $this->parse($buffer, $len, $off);
                        if ($key === null)
                            break;
                        if ($key[0] !== self::TYPE_TOKEN)
                            break;
                        $value = $this->parse($buffer, $len, $off);
                        $v[$key[1]] = $value;
                    }
                    $off+=2;
                    return array(self::TYPE_DICTIONARY, $v);
                } else {
                    // hex
                    $p = strpos($buffer, '>', $off);
                    if ($p !== false) {
                        $v = substr($buffer, $off + 1, $p - $off - 1);
                        $off = $p + 1;
                        return array(self::TYPE_HEX, $v);
                    }
                }
                break;
            case '(':
                // string
                $p = $off;
                while (1) {
                    $p++;
                    if ($p === $len)
                        break;
                    if (($buffer[$p] === ')') && ($buffer[$p - 1] !== '\\'))
                        break;
                }
                if ($p < $len) {
                    $v = substr($buffer, $off + 1, $p - $off - 1);
                    $off = $p + 1;
                    return array(self::TYPE_STRING, $v);
                }
                break;
            case '[':
                $v = array();
                $off++; // jump the [
                while (1) {
                    $value = $this->parse($buffer, $len, $off);
                    if ($value === null)
                        break;
                    $v[] = $value;
                }
                $off++; // jump the ]
                return array(self::TYPE_ARRAY, $v);
                break;
            case '>': // dictionnary : end
            case ']': // array : end
                return null;
                break;
            case '%': // comments : jump
                $p = strpos($buffer, "\n", $off);
                if ($p !== false) {
                    $off = $p + 1;
                    return $this->parse($buffer, $len, $off);
                }

                break;
            default:
                if (preg_match('`^\s*([0-9]+) 0 R`', substr($buffer, $off, 32), $m)) {
                    $off += strlen($m[0]);
                    return array(self::TYPE_REFERENCE, $m[1]);
                } else {
                    $p = strcspn($buffer, " %[]<>()\r\n\t/", $off + 1);
                    $v = substr($buffer, $off, $p + 1);
                    $off += $p + 1;
                    if (is_numeric($v)) {
                        $type = self::TYPE_NUMERIC;
                    } else if (($v === 'true') || ($v === 'false')) {
                        $type = self::TYPE_BOOL;
                    } else if ($v === 'null') {
                        $type = self::TYPE_NULL;
                    } else {
                        $type = self::TYPE_TOKEN;
                    }
                    return array($type, $v);
                }
                break;
        }
        return null;
    }

    private function getObject($f, $xref, $index, $includeSubObject = false) {

        $type = self::TYPE_TOKEN;

        if (!isset($xref[$index])) {
            $this->error('reference d\'object inconnue');
        }

        fseek($f, $xref[$index]);

        $data = '';
        $len = 0;
        $offset = 0;
        $expLen = 1024;
        do {
            $prev = $len;
            $data .= fread($f, $expLen);
            $len = strlen($data);
            $p = strpos($data, "endobj", $offset);
            if ($p !== false) {
                if ($data[$p - 1] !== "\n") {
                    $offset = $p + 6;
                    $p = false;
                } else {
                    if ($len < $p + 8) {
                        $data .= fread($f, 1);
                        $len = strlen($data);
                    }
                    if ($data[$p + 6] !== "\n") {
                        $offset = $p + 6; // not the endobj markup, maybe a string content
                        $p = false;
                    }
                }
            }
            $expLen *= 2;
        } while (($p === false) && ($prev !== $len));

        if ($p === false) {
            $this->error('object [' . $index . '] non trouve');
        }

        $p--;
        $data = substr($data, 0, $p);

        if (!preg_match('`^([0-9]+ 0 obj)`', $data, $m, PREG_OFFSET_CAPTURE)) {
            $this->error('object [' . $index . '] invalide');
        }

        $p = $m[0][1] + strlen($m[1][0]) + 1;
        $data = substr($data, $p);

        if (substr($data, 0, 2) === '<<') {
            $type = self::TYPE_DICTIONARY;
            $off = 0;
            $len = strlen($data);
            $dictionary = $this->parse($data, $len, $off);
            $off++;
            $data = substr($data, $off);
            if ($data === false) {
                $data = '';
            } else if (substr($data, 0, 7) === "stream\n") {
                $data = substr($data, 7, strlen($data) - 17);
                $type = self::TYPE_STREAM;
            }
            if ($includeSubObject) {
                $dictionary = $this->_resolveValues($f, $xref, $dictionary);
            }
        } else {
            $dictionary = null;
        }
        return array($type, $dictionary, $data);
    }

    private function _resolveValues($f, $xref, $item) {
        switch ($item[0]) {
            case self::TYPE_REFERENCE:
                $object = $this->getObject($f, $xref, $item[1], true);
                if ($object[0] === self::TYPE_TOKEN) {
                    return array(self::TYPE_TOKEN, $object[2]);
                }
                $ref = $this->storeObject($object);
                return array(self::TYPE_REFERENCE_F, $this->_getObjectType($object), $ref);
                break;
            case self::TYPE_ARRAY:
            case self::TYPE_DICTIONARY:
                $r = array();
                foreach ($item[1] as $key => $val) {
                    if (($val[0] == self::TYPE_REFERENCE) ||
                            ($val[0] == self::TYPE_ARRAY) ||
                            ($val[0] == self::TYPE_DICTIONARY)) {
                        $r[$key] = $this->_resolveValues($f, $xref, $val);
                    } else {
                        $r[$key] = $val;
                    }
                }
                return array($item[0], $r);
                break;
            default:
                return $item;
        }
    }

    private function getResources($f, $xref, $page) {
        if ($page[0] !== self::TYPE_DICTIONARY) {
            $this->error('getResources necessite un dictionaire');
        }
        if (isset($page[1]['/Resources'])) {
            if ($page[1]['/Resources'][0] === self::TYPE_REFERENCE) {
                return $this->getObject($f, $xref, $page[1]['/Resources'][1]);
            } else {
                return array($page[1]['/Resources'][1]);
            }
        } else if (isset($page[1]['/Parent'])) {
            return $this->getResources($f, $xref, $page[1]['/Parent']);
        }
        return null;
    }

    private function getContent($f, $xref, $page) {
        if ($page[0] !== self::TYPE_DICTIONARY) {
            $this->error('getContent necessite un dictionaire');
        }
        $stream = '';
        if (isset($page[1]['/Contents'])) {
            $stream = $this->_getContent($f, $xref, $page[1]['/Contents']);
        }
        return $stream;
    }

    private function _getContent($f, $xref, $content) {
        $stream = '';
        if ($content[0] === self::TYPE_REFERENCE) {
            $stream .= $this->getStream($f, $xref, $this->getObject($f, $xref, $content[1]));
        } else if ($content[0] === self::TYPE_ARRAY) {
            foreach ($content[1] as $sub) {
                $stream .= $this->_getContent($f, $xref, $sub);
            }
        } else {
            $stream .= $this->getStream($f, $xref, $item);
        }
        return $stream;
    }

    private function getCompression($f, $xref, $item) {
        if ($item[0] === self::TYPE_TOKEN) {
            return array($item[1]);
        } else if ($item[0] === self::TYPE_ARRAY) {
            $r = array();
            foreach ($item[1] as $sub) {
                $r = array_merge($r, $this->getCompression($f, $xref, $sub));
            }
            return $r;
        } else if ($item[0] === self::TYPE_REFERENCE) {
            return $this->getCompression($f, $xref, $this->getObject($f, $xref, $item[1]));
        }
        return array();
    }

    private function getStream($f, $xref, $item) {
        $methods = isset($item[1][1]['/Filter']) ? $this->getCompression($f, $xref, $item[1][1]['/Filter']) : array();

        $raw = $item[2];
        foreach ($methods as $method) {
            switch ($method) {
                case '/FlateDecode':
                    if (function_exists('gzuncompress')) {
                        $raw = !empty($raw) ? @gzuncompress($raw) : '';
                    } else {
                        $this->error('gzuncompress necessaire pour decompresser ce stream');
                    }
                    if ($raw === false) {
                        $this->error('erreur de decompression du stream');
                    }
                    break;
                default:
                    $this->error($method . ' necessaire pour decompresser ce stream');
            }
        }
        return $raw;
    }

    private function storeObject($item, $type = false) {
        $md5 = md5(serialize($item));
        if ($type === '/Font') {
            $array = & $this->fonts;
            $prefix = '/F';
        } else {
            $array = & $this->objects;
            $prefix = '/Obj';
        }
        if (!isset($array[$md5])) {
            $index = count($array) + 1;
            $array[$md5] = array(
                'name' => $prefix . $index,
                'item' => $item,
                'type' => $type,
                'index' => $index
            );
        } else if ($type) {
            $array[$md5]['type'] = $type;
        }
        return $array[$md5][$type ? 'name' : 'index'];
    }

    //================================================
    // FONCTIONS D'IMPRESSION
    //================================================

    private function _out($raw) {
        $this->buffer .= $raw . "\n";
    }

    private function _strval($value) {
        $value+=0;
        if ($value) {
            return strval($value);
        }
        return '0';
    }

    private function _toStream($item) {
        switch ($item[0]) {
            case self::TYPE_NULL : return 'null';
            case self::TYPE_TOKEN : return $item[1];
            case self::TYPE_REFERENCE : return $this->_strval($item[1]) . ' 0 R';
            case self::TYPE_REFERENCE_F :
                if (!isset($this->ref[$item[1]][$item[2]])) {
                    $this->error('reference vers un object non sauve');
                }
                return $this->_strval($this->ref[$item[1]][$item[2]]) . ' 0 R';

            case self::TYPE_NUMERIC : return $this->_strval($item[1]);
            case self::TYPE_HEX : return '<' . strval($item[1]) . '>';
            case self::TYPE_BOOL : return $item[1] ? 'true' : 'false';
            case self::TYPE_STRING : return '(' . str_replace(array('\\', '(', ')'), array('\\\\', '\\(', '\\)'), strval($item[1])) . ')';
            case self::TYPE_ARRAY :
                $r = array();
                foreach ($item[1] as $val) {
                    $r[] = $this->_toStream($val);
                }
                return '[' . implode(' ', $r) . ']';
            case self::TYPE_DICTIONARY :
                $r = array();
                foreach ($item[1] as $key => $val) {
                    $val = $this->_toStream($val);
                    $r[] = $key . ' ' . $val;
                }
                return '<<' . implode("\n", $r) . '>>';
                break;
        }
        return '';
    }

    private function _newobj($n = null) {
        if (($n === null) || ($n === true)) {
            $this->n++;
            $id = $this->n;
        } else {
            $id = $n;
        }
        if ($n !== true) {
            $this->xref[$id] = strlen($this->buffer);
            $this->_out($id . ' 0 obj');
        }
        return $id;
    }

    private function _addObj($dico = null, $buf = null) {
        $ref = $this->_newobj();
        $buf = empty($buf) && ($buf !== 0) && ($buf !== '0') ? null : $buf;
        if (is_array($dico)) {
            if ($buf !== null) {
                if ($this->compress && !isset($dico['/Filter'])) {
                    $buf = gzcompress($buf);
                    $dico['/Filter'] = array(self::TYPE_TOKEN, '/FlateDecode');
                }
                $dico['/Length'] = array(self::TYPE_NUMERIC, strlen($buf));
            }
            $this->_out($this->_toStream(array(self::TYPE_DICTIONARY, $dico)));
        }
        if ($buf !== null) {
            $this->_out('stream');
            $this->_out($buf);
            $this->_out('endstream');
        }
        $this->_out('endobj');
        return $ref;
    }

    private function _getObjectType($object) {
        return isset($object['type']) && !empty($object['type']) ? $object['type'] : 'default';
    }

    private function _putObject($object) {
        $type = $this->_getObjectType($object);
        if (!isset($this->ref[$type])) {
            $this->ref[$type] = array();
        }
        $this->ref[$type][$object['index']] = $this->_addObj($object['item'][1][1], $object['item'][2]);
    }

    private function _putObjects() {
        foreach ($this->objects as $object) {
            if ($object['type'])
                continue;
            $this->_putObject($object);
        }
        foreach ($this->objects as $object) {
            if (!$object['type'])
                continue;
            $this->_putObject($object);
        }
        foreach ($this->fonts as $object) {
            $this->_putObject($object);
        }
    }

    private function _putResources() {
        $dico = array(
            '/ProcSet' => array(
                self::TYPE_ARRAY,
                array(
                    array(self::TYPE_TOKEN, '/PDF'),
                    array(self::TYPE_TOKEN, '/Text'),
                    array(self::TYPE_TOKEN, '/ImageB'),
                    array(self::TYPE_TOKEN, '/ImageC'),
                    array(self::TYPE_TOKEN, '/ImageI')
                )
            )
        );

        $xObjects = array();
        foreach ($this->objects as $index => $object) {
            if ($object['type'] === false) {
                continue;
            }
            $value = array(
                self::TYPE_TOKEN,
                $this->_toStream(array(self::TYPE_REFERENCE, $this->ref[$object['type']][$object['index']]))
            );
            if ($object['type'] === '/XObject') {
                $xObjects[$object['name']] = $value;
            }
        }
        if (!empty($xObjects)) {
            $dico['/XObject'] = array(self::TYPE_DICTIONARY, $xObjects);
        }

        $fonts = array();
        foreach ($this->fonts as $index => $object) {
            $value = array(
                self::TYPE_TOKEN,
                $this->_toStream(array(self::TYPE_REFERENCE, $this->ref['/Font'][$object['index']]))
            );
            $fonts[$object['name']] = $value;
        }
        if (!empty($fonts)) {
            $dico['/Font'] = array(self::TYPE_DICTIONARY, $fonts);
        }
        return $this->_addObj($dico);
    }

    /*     * ************************************************
      /*                      PUBLIC
      /************************************************* */

    public function add($filename) {
        $f = @fopen($filename, 'rb');
        if (!$f) {
            $this->error('impossible d\'ouvrir le fichier');
        }
        fseek($f, 0, SEEK_END);
        $fileLength = ftell($f);

        // Localisation de xref
        //-------------------------------------------------

        fseek($f, -128, SEEK_END);
        $data = fread($f, 128);
        if ($data === false) {
            return $this->error('erreur de lecture dans le fichier');
        }
        $p = strripos($data, 'startxref');
        if ($p === false) {
            return $this->error('startxref absent');
        }
        $startxref = substr($data, $p + 10, strlen($data) - $p - 17);
        $posStartxref = $fileLength - 128 + $p;

        // extraction de xref + trailer
        //-------------------------------------------------

        fseek($f, $startxref);
        $data = fread($f, $posStartxref - $startxref);

        // extraction du trailer
        //-------------------------------------------------
        $p = stripos($data, 'trailer');
        if ($p === false) {
            return $this->error('trailer absent');
        }
        $dataTrailer = substr($data, $p + 8);
        $len = strlen($dataTrailer);
        $off = 0;
        $trailer = $this->parse($dataTrailer, $len, $off);

        // extraction du xref
        //-------------------------------------------------

        $data = explode("\n", trim(substr($data, 0, $p)));
        array_shift($data); // "xref"

        $cnt = 0;
        $xref = array();

        foreach ($data as $line) {
            if (!$cnt) {
                if (preg_match('`^([0-9]+) ([0-9]+)$`', $line, $m)) {
                    $index = intval($m[1]) - 1;
                    $cnt = intval($m[2]);
                } else {
                    $this->error('erreur dans xref');
                }
            } else {
                $index++;
                $cnt--;
                if (preg_match('`^([0-9]{10}) [0-9]{5} ([n|f])`', $line, $m)) {
                    if ($m[2] === 'f') {
                        continue;
                    }
                    $xref[$index] = $m[1];
                } else {
                    $this->error('erreur dans xref : ' . $line);
                }
            }
        }

        // Lecture des pages
        //-------------------------------------------------

        $root = $this->getObject($f, $xref, $trailer[1]['/Root'][1]);
        $root = $root[1][1];

        $pages = $this->getObject($f, $xref, $root['/Pages'][1]);
        $pages = $pages[1][1];

        foreach ($pages['/Kids'][1] as $kid) {
            $kid = $this->getObject($f, $xref, $kid[1]);
            $kid = $kid[1];

            $resources = $this->getResources($f, $xref, $kid);
            $resources = $resources[1][1];

            $content = $this->getContent($f, $xref, $kid);

            // traitement des fonts
            //-------------------------------------------------
            $newFonts = array();
            if (isset($resources['/Font']) && !empty($resources['/Font'])) {
                if (preg_match_all("`(/F[0-9]+)\s+-?[0-9\.]+\s+Tf`", $content, $matches, PREG_OFFSET_CAPTURE)) {
                    $newContent = '';
                    $offset = 0;
                    $cnt = count($matches[0]);
                    for ($i = 0; $i < $cnt; $i++) {
                        $position = $matches[0][$i][1];
                        $name = $matches[1][$i][0];
                        if (!isset($newFonts[$name])) {
                            $object = $this->getObject($f, $xref, $resources['/Font'][1][$name][1], true);
                            $newFonts[$name] = $this->storeObject($object, '/Font');
                        }
                        if ($newFonts[$name] !== $name) {
                            $newContent .= substr($content, $offset, $position - $offset);
                            $newContent .= $newFonts[$name];
                            $offset = $position + strlen($name);
                        }
                    }
                    $content = $newContent . substr($content, $offset);
                }
            }

            // traitement des XObjets
            //-------------------------------------------------
            $newXObjects = array();
            if (isset($resources['/XObject']) && !empty($resources['/XObject'])) {
                if (preg_match_all("`(/[^%\[\]<>\(\)\r\n\t/]+) Do`", $content, $matches, PREG_OFFSET_CAPTURE)) {
                    $newContent = '';
                    $offset = 0;
                    foreach ($matches[1] as $m) {
                        $name = $m[0];
                        $position = $m[1];
                        if (!isset($newXObjects[$name])) {
                            $object = $this->getObject($f, $xref, $resources['/XObject'][1][$name][1], true);
                            $newXObjects[$name] = $this->storeObject($object, '/XObject');
                        }
                        if ($newXObjects[$name] !== $name) {
                            $newContent .= substr($content, $offset, $position - $offset);
                            $newContent .= $newXObjects[$name];
                            $offset = $position + strlen($name);
                        }
                    }
                    $content = $newContent . substr($content, $offset);
                }
            }

            $mediaBox = isset($kid[1]['/MediaBox']) ? $kid[1]['/MediaBox'] : (isset($pages['/MediaBox']) ? $pages['/MediaBox'] : null);

            if ($mediaBox[0] !== self::TYPE_ARRAY) {
                $this->error('MediaBox non definie');
            }


            $this->pages[] = array(
                'content' => $content,
                '/XObject' => array_values($newXObjects),
                '/Font' => array_values($newFonts),
                '/MediaBox' => $mediaBox
            );
        }
        fclose($f);
    }

    public function output($filename = null) {
        $this->_out('%PDF-1.6');

        $this->_putObjects();

        $rsRef = $this->_putResources();

        $ptRef = $this->_newobj(true);

        $kids = array();

        // Ajout des pages 
        $n = count($this->pages);
        for ($i = 0; $i < $n; $i++) {
            $ctRef = $this->_addObj(array(), $this->pages[$i]['content']);
            $dico = array(
                '/Type' => array(self::TYPE_TOKEN, '/Page'),
                '/Parent' => array(self::TYPE_REFERENCE, $ptRef),
                '/MediaBox' => $this->pages[$i]['/MediaBox'],
                '/Resources' => array(self::TYPE_REFERENCE, $rsRef),
                '/Contents' => array(self::TYPE_REFERENCE, $ctRef),
            );
            $kids[] = array(self::TYPE_REFERENCE, $this->_addObj($dico));
        }

        // Ajout du page tree
        $ptDico = array(
            self::TYPE_DICTIONARY,
            array(
                '/Type' => array(self::TYPE_TOKEN, '/Pages'),
                '/Kids' => array(self::TYPE_ARRAY, $kids),
                '/Count' => array(self::TYPE_NUMERIC, count($kids))
            )
        );

        $this->_newobj($ptRef);
        $this->_out($this->_toStream($ptDico));
        $this->_out('endobj');

        // Ajout du catalogue
        $ctDico = array(
            self::TYPE_DICTIONARY,
            array(
                '/Type' => array(self::TYPE_TOKEN, '/Calalog'),
                '/Pages' => array(self::TYPE_REFERENCE, $ptRef)
            )
        );
        $ctRef = $this->_newobj();
        $this->_out($this->_toStream($ctDico));
        $this->_out('endobj');

        // Ajout du xref
        $xrefOffset = strlen($this->buffer);
        $count = count($this->xref);
        $this->_out('xref');
        $this->_out('0 ' . ($count + 1));
        $this->_out('0000000000 65535 f ');
        for ($i = 0; $i < $count; $i++) {
            $this->_out(sprintf('%010d 00000 n ', $this->xref[$i + 1]));
        }

        // Ajout du trailer
        $dico = array(
            '/Size' => array(self::TYPE_NUMERIC, 1 + count($this->xref)),
            '/Root' => array(self::TYPE_REFERENCE, $ctRef)
        );
        $this->_out('trailer');
        $this->_out($this->_toStream(array(self::TYPE_DICTIONARY, $dico)));


        // Ajout du startxref
        $this->_out('startxref');
        $this->_out($xrefOffset);
        $this->_out('%%EOF');

        if ($filename === null) {
            header('Content-Type: application/pdf');
            header('Content-Length: ' . strlen($this->buffer));
            header('Cache-Control: private, max-age=0, must-revalidate');
            header('Pragma: public');
            ini_set('zlib.output_compression', '0');

            echo $this->buffer;
            die;
        } else {
            file_put_contents($filename, $this->buffer);
        }
    }

}

?>