<?php

    namespace GifCreator;

    /**
     * Create an animated GIF from multiple images
     * @version   1.0
     * @link      https://github.com/Sybio/GifCreator
     * @author    Sybio (Clément Guillemain  / @Sybio01)
     * @license   http://opensource.org/licenses/gpl-license.php GNU Public License
     * @copyright Clément Guillemain
     * @modified by Max Korlaar
     */
    class GifCreator {
        /**
         * @var string The gif string source (old: this->GIF)
         */
        private $gif;

        /**
         * @var string Encoder version (old: this->VER)
         */
        private $version;

        /**
         * @var boolean Check the image is build or not (old: this->IMG)
         */
        private $imgBuilt;

        /**
         * @var array Frames string sources (old: this->BUF)
         */
        private $frameSources;

        /**
         * @var integer Gif loop (old: this->LOP)
         */
        private $loop;

        /**
         * @var integer Gif dis (old: this->DIS)
         */
        private $dis;

        /**
         * @var integer Gif color (old: this->COL)
         */
        private $colour;

        /**
         * @var array (old: this->ERR)
         */
        private $errors;

        // Methods
        // ===================================================================================

        /**
         * Constructor
         */
        public function __construct() {
            $this->reset();

            // Static data
            $this->version = 'GifCreator: Under development';
            $this->errors  = array(
                'ERR00' => 'Does not supported function for only one image.',
                'ERR01' => 'Source is not a GIF image.',
                'ERR02' => 'You have to give resource image variables, image URL or image binary sources in $frames array.',
                'ERR03' => 'Does not make animation from animated GIF source.',
            );
        }

        /**
         * Create the GIF string (old: GIFEncoder)
         *
         * @param array   $frames    An array of frame: can be file paths, resource image variables, binary sources or image URLs
         * @param array   $durations An array containing the duration of each frame
         * @param integer $loop      Number of GIF loops before stopping animation (Set 0 to get an infinite loop)
         *
         * @throws \Exception
         * @return string The GIF string source
         */
        public function create($frames = array(), $durations = array(), $loop = 0) {
            if (!is_array($frames) && !is_array($durations)) {

                throw new \Exception($this->version . ': ' . $this->errors['ERR00']);
            }

            $this->loop = ($loop > -1) ? $loop : 0;
            $this->dis  = 2;

            for ($i = 0; $i < count($frames); $i++) {

                if (is_resource($frames[$i])) { // Resource var

                    $resourceImg = $frames[$i];

                    ob_start();
                    imagegif($frames[$i]);
                    $this->frameSources[] = ob_get_contents();
                    ob_end_clean();

                } elseif (is_string($frames[$i])) { // File path or URL or Binary source code

                    if (file_exists($frames[$i]) || filter_var($frames[$i], FILTER_VALIDATE_URL)) { // File path

                        $frames[$i] = file_get_contents($frames[$i]);
                    }

                    $resourceImg = imagecreatefromstring($frames[$i]);

                    ob_start();
                    imagegif($resourceImg);
                    $this->frameSources[] = ob_get_contents();
                    ob_end_clean();

                } else { // Fail

                    throw new \Exception($this->version . ': ' . $this->errors['ERR02']);
                }

                if ($i == 0) {

                    $colour = imagecolortransparent($resourceImg);
                }

                if (substr($this->frameSources[$i], 0, 6) != 'GIF87a' && substr($this->frameSources[$i], 0, 6) != 'GIF89a') {

                    throw new \Exception($this->version . ': ' . $i . ' ' . $this->errors['ERR01']);
                }

                for ($j = (13 + 3 * (2 << (ord($this->frameSources[$i]{10}) & 0x07))), $k = true; $k; $j++) {

                    switch ($this->frameSources[$i]{$j}) {

                        case '!':

                            if ((substr($this->frameSources[$i], ($j + 3), 8)) == 'NETSCAPE') {

                                throw new \Exception($this->version . ': ' . $this->errors['ERR03'] . ' (' . ($i + 1) . ' source).');
                            }

                            break;

                        case ';':

                            $k = false;
                            break;
                    }
                }

                unset($resourceImg);
            }

            if (isset($colour)) {

                $this->colour = $colour;

            } else {

                $red          = $green = $blue = 0;
                $this->colour = ($red > -1 && $green > -1 && $blue > -1) ? ($red | ($green << 8) | ($blue << 16)) : -1;
            }

            $this->gifAddHeader();

            for ($i = 0; $i < count($this->frameSources); $i++) {

                $this->addGifFrames($i, $durations[$i]);
            }

            $this->gifAddFooter();

            return $this->gif;
        }

        // Internals
        // ===================================================================================

        /**
         * Add the header gif string in its source (old: GIFAddHeader)
         */
        public function gifAddHeader() {
            $cmap = 0;

            if (ord($this->frameSources[0]{10}) & 0x80) {

                $cmap = 3 * (2 << (ord($this->frameSources[0]{10}) & 0x07));

                $this->gif .= substr($this->frameSources[0], 6, 7);
                $this->gif .= substr($this->frameSources[0], 13, $cmap);
                $this->gif .= "!\377\13NETSCAPE2.0\3\1" . $this->encodeAsciiToChar($this->loop) . "\0";
            }
        }

        /**
         * Add the frame sources to the GIF string (old: GIFAddFrames)
         *
         * @param integer $i
         * @param integer $d
         */
        public function addGifFrames($i, $d) {
            $Locals_str = 13 + 3 * (2 << (ord($this->frameSources[$i]{10}) & 0x07));

            $Locals_end = strlen($this->frameSources[$i]) - $Locals_str - 1;
            $Locals_tmp = substr($this->frameSources[$i], $Locals_str, $Locals_end);

            $Global_len = 2 << (ord($this->frameSources[0]{10}) & 0x07);
            $Locals_len = 2 << (ord($this->frameSources[$i]{10}) & 0x07);

            $Global_rgb = substr($this->frameSources[0], 13, 3 * (2 << (ord($this->frameSources[0]{10}) & 0x07)));
            $Locals_rgb = substr($this->frameSources[$i], 13, 3 * (2 << (ord($this->frameSources[$i]{10}) & 0x07)));

            $Locals_ext = "!\xF9\x04" . chr(($this->dis << 2) + 0) . chr(($d >> 0) & 0xFF) . chr(($d >> 8) & 0xFF) . "\x0\x0";

            if ($this->colour > -1 && ord($this->frameSources[$i]{10}) & 0x80) {

                for ($j = 0; $j < (2 << (ord($this->frameSources[$i]{10}) & 0x07)); $j++) {

                    if (ord($Locals_rgb{3 * $j + 0}) == (($this->colour >> 16) & 0xFF) &&
                        ord($Locals_rgb{3 * $j + 1}) == (($this->colour >> 8) & 0xFF) &&
                        ord($Locals_rgb{3 * $j + 2}) == (($this->colour >> 0) & 0xFF)
                    ) {
                        $Locals_ext = "!\xF9\x04" . chr(($this->dis << 2) + 1) . chr(($d >> 0) & 0xFF) . chr(($d >> 8) & 0xFF) . chr($j) . "\x0";
                        break;
                    }
                }
            }

            switch ($Locals_tmp{0}) {

                case '!':

                    $Locals_img = substr($Locals_tmp, 8, 10);
                    $Locals_tmp = substr($Locals_tmp, 18, strlen($Locals_tmp) - 18);

                    break;

                case ',':

                    $Locals_img = substr($Locals_tmp, 0, 10);
                    $Locals_tmp = substr($Locals_tmp, 10, strlen($Locals_tmp) - 10);

                    break;
            }

            if (ord($this->frameSources[$i]{10}) & 0x80 && $this->imgBuilt) {

                if ($Global_len == $Locals_len) {

                    if ($this->gifBlockCompare($Global_rgb, $Locals_rgb, $Global_len)) {

                        $this->gif .= $Locals_ext . $Locals_img . $Locals_tmp;

                    } else {

                        $byte = ord($Locals_img{9});
                        $byte |= 0x80;
                        $byte &= 0xF8;
                        $byte |= (ord($this->frameSources[0]{10}) & 0x07);
                        $Locals_img{9} = chr($byte);
                        $this->gif .= $Locals_ext . $Locals_img . $Locals_rgb . $Locals_tmp;
                    }

                } else {

                    $byte = ord($Locals_img{9});
                    $byte |= 0x80;
                    $byte &= 0xF8;
                    $byte |= (ord($this->frameSources[$i]{10}) & 0x07);
                    $Locals_img{9} = chr($byte);
                    $this->gif .= $Locals_ext . $Locals_img . $Locals_rgb . $Locals_tmp;
                }

            } else {

                $this->gif .= $Locals_ext . $Locals_img . $Locals_tmp;
            }

            $this->imgBuilt = true;
        }

        /**
         * Add the gif string footer char (old: GIFAddFooter)
         */
        public function gifAddFooter() {
            $this->gif .= ';';
        }

        /**
         * Compare two block and return the version (old: GIFBlockCompare)
         *
         * @param string  $globalBlock
         * @param string  $localBlock
         * @param integer $length
         *
         * @return integer
         */
        public function gifBlockCompare($globalBlock, $localBlock, $length) {
            for ($i = 0; $i < $length; $i++) {

                if ($globalBlock{3 * $i + 0} != $localBlock{3 * $i + 0} ||
                    $globalBlock{3 * $i + 1} != $localBlock{3 * $i + 1} ||
                    $globalBlock{3 * $i + 2} != $localBlock{3 * $i + 2}
                ) {

                    return 0;
                }
            }

            return 1;
        }

        /**
         * Encode an ASCII char into a string char (old: GIFWord)
         * $param integer $char ASCII char
         *
         * @param $char
         *
         * @return string
         */
        public function encodeAsciiToChar($char) {
            return (chr($char & 0xFF) . chr(($char >> 8) & 0xFF));
        }

        /**
         * Reset and clean the current object
         */
        public function reset() {
            $this->frameSources;
            $this->gif      = 'GIF89a'; // the GIF header
            $this->imgBuilt = false;
            $this->loop     = 0;
            $this->dis      = 2;
            $this->colour   = -1;
        }

        // Getter / Setter
        // ===================================================================================

        /**
         * Get the final GIF image string (old: GetAnimation)
         * @return string
         */
        public function getGif() {
            return $this->gif;
        }
    }