<?php

namespace App\Services;

class AnimatedGifService
{
    /**
     * Check if a GIF file at a path is animated or not
     *
     * @param string  $filenameOrBlob GIF file path or data blob if dataSize > 0.
     * @param integer $dataSize       GIF blob size.
     * @return boolean GIF file/blob is animated.
     */
    public static function isAnimatedGif(string $filenameOrBlob, int $dataSize = 0): bool
    {
        $regex = '#\x00\x21\xF9\x04.{4}\x00(\x2C|\x21)#s';
        $count = 0;

        if ($dataSize > 0) {
            if (($fh = @fopen($filenameOrBlob, 'rb')) === false) {
                return false;
            }

            $chunk = false;
            while (feof($fh) === false && $count < 2) {
                $chunk = ($chunk !== '' ? substr($chunk, -20) : "") . fread($fh, (1024 * 100)); //read 100kb at a time
                $count += preg_match_all($regex, $chunk, $matches);
            }

            fclose($fh);
        } else {
            $count = preg_match_all($regex, $filenameOrBlob, $matches);
        }

        return $count > 1;
    }

    /**
     * Extract frames of a GIF
     *
     * @param string  $filenameOrBlob GIF filename path
     * @param integer $dataSize       GIF blob size.
     * @param boolean $originalFrames Get original frames (with transparent background)
     */
    public function extract(string $filenameOrBlob, int $dataSize = 0, bool $originalFrames = false): array
    {
        if (self::isAnimatedGif($filenameOrBlob) === false) {
            return [];
        }

        $this->reset();
        $this->parseFramesInfo($filename);
        $prevImg = null;

        for ($i = 0; $i < count($this->frameSources); $i++) {
            $this->frames[$i] = [];
            $this->frameDurations[$i] = $this->frames[$i]['duration'] = $this->frameSources[$i]['delay_time'];

            $img = imagecreatefromstring($this->fileHeader["gifheader"] . $this->frameSources[$i]["graphicsextension"] . $this->frameSources[$i]["imagedata"] . chr(0x3b));

            if (!$originalFrames) {
                if ($i > 0) {
                    $prevImg = $this->frames[($i - 1)]['image'];
                } else {
                    $prevImg = $img;
                }

                $sprite = imagecreate($this->gifMaxWidth, $this->gifMaxHeight);
                imagesavealpha($sprite, true);

                $transparent = imagecolortransparent($prevImg);

                if ($transparent > -1 && imagecolorstotal($prevImg) > $transparent) {
                    $actualTrans = imagecolorsforindex($prevImg, $transparent);
                    imagecolortransparent($sprite, imagecolorallocate($sprite, $actualTrans['red'], $actualTrans['green'], $actualTrans['blue']));
                }

                if ((int) $this->frameSources[$i]['disposal_method'] == 1 && $i > 0) {
                    imagecopy($sprite, $prevImg, 0, 0, 0, 0, $this->gifMaxWidth, $this->gifMaxHeight);
                }

                imagecopyresampled($sprite, $img, $this->frameSources[$i]["offset_left"], $this->frameSources[$i]["offset_top"], 0, 0, $this->gifMaxWidth, $this->gifMaxHeight, $this->gifMaxWidth, $this->gifMaxHeight);
                $img = $sprite;
            }//end if

            $this->frameImages[$i] = $this->frames[$i]['image'] = $img;
        }//end for

        return $this->frames;
    }
}

class GifFrameExtractor
{
    // Properties
    // ===================================================================================

    /**
     * @var resource
     */
    private $gif;

    /**
     * @var array
     */
    private $frames;

    /**
     * @var array
     */
    private $frameDurations;

    /**
     * @var array
     */
    private $frameImages;

    /**
     * @var array
     */
    private $framePositions;

    /**
     * @var array
     */
    private $frameDimensions;

    /**
     * @var integer
     *
     * (old: $this->index)
     */
    private $frameNumber;

    /**
     * @var array
     *
     * (old: $this->imagedata)
     */
    private $frameSources;

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

    /**
     * @var integer The reader pointer in the file source
     *
     * (old: $this->pointer)
     */
    private $pointer;

    /**
     * @var integer
     */
    private $gifMaxWidth;

    /**
     * @var integer
     */
    private $gifMaxHeight;

    /**
     * @var integer
     */
    private $totalDuration;

    /**
     * @var integer
     */
    private $handle;

    /**
     * @var array
     *
     * (old: globaldata)
     */
    private $globaldata;

    /**
     * @var array
     *
     * (old: orgvars)
     */
    private $orgvars;

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


    /**
     * Parse the frame informations contained in the GIF file
     *
     * @param string $filename GIF filename path
     */
    private function parseFramesInfo(string $filename)
    {
        $this->openFile($filename);
        $this->parseGifHeader();
        $this->parseGraphicsExtension(0);
        $this->getApplicationData();
        $this->getApplicationData();
        $this->getFrameString(0);
        $this->parseGraphicsExtension(1);
        $this->getCommentData();
        $this->getApplicationData();
        $this->getFrameString(1);

        while (!$this->checkByte(0x3b) && !$this->checkEOF()) {
            $this->getCommentData(1);
            $this->parseGraphicsExtension(2);
            $this->getFrameString(2);
            $this->getApplicationData();
        }
    }

    /**
     * Parse the gif header (old: get_gif_header)
     */
    private function parseGifHeader()
    {
        $this->pointerForward(10);

        if ($this->readBits(($mybyte = $this->readByteInt()), 0, 1) == 1) {
            $this->pointerForward(2);
            $this->pointerForward(pow(2, ($this->readBits($mybyte, 5, 3) + 1)) * 3);
        } else {
            $this->pointerForward(2);
        }

        $this->fileHeader["gifheader"] = $this->dataPart(0, $this->pointer);

        // Decoding
        $this->orgvars["gifheader"] = $this->fileHeader["gifheader"];
        $this->orgvars["background_color"] = $this->orgvars["gifheader"][11];
    }

    /**
     * Parse the application data of the frames (old: get_application_data)
     */
    private function getApplicationData()
    {
        $startdata = $this->readByte(2);

        if ($startdata == chr(0x21) . chr(0xff)) {
            $start = ($this->pointer - 2);
            $this->pointerForward($this->readByteInt());
            $this->readDataStream($this->readByteInt());
            $this->fileHeader["applicationdata"] = $this->dataPart($start, ($this->pointer - $start));
        } else {
            $this->pointerRewind(2);
        }
    }

    /**
     * Parse the comment data of the frames (old: get_comment_data)
     */
    private function getCommentData()
    {
        $startdata = $this->readByte(2);

        if ($startdata == chr(0x21) . chr(0xfe)) {
            $start = ($this->pointer - 2);
            $this->readDataStream($this->readByteInt());
            $this->fileHeader["commentdata"] = $this->dataPart($start, ($this->pointer - $start));
        } else {
            $this->pointerRewind(2);
        }
    }

    /**
     * Parse the graphic extension of the frames (old: get_graphics_extension)
     */
    private function parseGraphicsExtension(int $type)
    {
        $startdata = $this->readByte(2);

        if ($startdata == chr(0x21) . chr(0xf9)) {
            $start = ($this->pointer - 2);
            $this->pointerForward($this->readByteInt());
            $this->pointerForward(1);

            if ($type == 2) {
                $this->frameSources[$this->frameNumber]["graphicsextension"] = $this->dataPart($start, ($this->pointer - $start));
            } elseif ($type == 1) {
                $this->orgvars["hasgx_type_1"] = 1;
                $this->globaldata["graphicsextension"] = $this->dataPart($start, ($this->pointer - $start));
            } elseif ($type == 0) {
                $this->orgvars["hasgx_type_0"] = 1;
                $this->globaldata["graphicsextension_0"] = $this->dataPart($start, ($this->pointer - $start));
            }
        } else {
            $this->pointerRewind(2);
        }//end if
    }

    /**
     * Get the full frame string block (old: get_image_block)
     */
    private function getFrameString(int $type)
    {
        if ($this->checkByte(0x2c)) {
            $start = $this->pointer;
            $this->pointerForward(9);

            if ($this->readBits(($mybyte = $this->readByteInt()), 0, 1) == 1) {
                $this->pointerForward(pow(2, ($this->readBits($mybyte, 5, 3) + 1)) * 3);
            }

            $this->pointerForward(1);
            $this->readDataStream($this->readByteInt());
            $this->frameSources[$this->frameNumber]["imagedata"] = $this->dataPart($start, ($this->pointer - $start));

            if ($type == 0) {
                $this->orgvars["hasgx_type_0"] = 0;

                if (isset($this->globaldata["graphicsextension_0"])) {
                    $this->frameSources[$this->frameNumber]["graphicsextension"] = $this->globaldata["graphicsextension_0"];
                } else {
                    $this->frameSources[$this->frameNumber]["graphicsextension"] = null;
                }

                unset($this->globaldata["graphicsextension_0"]);
            } elseif ($type == 1) {
                if (isset($this->orgvars["hasgx_type_1"]) && $this->orgvars["hasgx_type_1"] == 1) {
                    $this->orgvars["hasgx_type_1"] = 0;
                    $this->frameSources[$this->frameNumber]["graphicsextension"] = $this->globaldata["graphicsextension"];
                    unset($this->globaldata["graphicsextension"]);
                } else {
                    $this->orgvars["hasgx_type_0"] = 0;
                    $this->frameSources[$this->frameNumber]["graphicsextension"] = $this->globaldata["graphicsextension_0"];
                    unset($this->globaldata["graphicsextension_0"]);
                }
            }//end if

            $this->parseFrameData();
            $this->frameNumber++;
        }//end if
    }

    /**
     * Parse frame data string into an array (old: parse_image_data)
     */
    private function parseFrameData()
    {
        $this->frameSources[$this->frameNumber]["disposal_method"] = $this->getImageDataBit("ext", 3, 3, 3);
        $this->frameSources[$this->frameNumber]["user_input_flag"] = $this->getImageDataBit("ext", 3, 6, 1);
        $this->frameSources[$this->frameNumber]["transparent_color_flag"] = $this->getImageDataBit("ext", 3, 7, 1);
        $this->frameSources[$this->frameNumber]["delay_time"] = $this->dualByteVal($this->getImageDataByte("ext", 4, 2));
        $this->totalDuration += (int) $this->frameSources[$this->frameNumber]["delay_time"];
        $this->frameSources[$this->frameNumber]["transparent_color_index"] = ord($this->getImageDataByte("ext", 6, 1));
        $this->frameSources[$this->frameNumber]["offset_left"] = $this->dualByteVal($this->getImageDataByte("dat", 1, 2));
        $this->frameSources[$this->frameNumber]["offset_top"] = $this->dualByteVal($this->getImageDataByte("dat", 3, 2));
        $this->frameSources[$this->frameNumber]["width"] = $this->dualByteVal($this->getImageDataByte("dat", 5, 2));
        $this->frameSources[$this->frameNumber]["height"] = $this->dualByteVal($this->getImageDataByte("dat", 7, 2));
        $this->frameSources[$this->frameNumber]["local_color_table_flag"] = $this->getImageDataBit("dat", 9, 0, 1);
        $this->frameSources[$this->frameNumber]["interlace_flag"] = $this->getImageDataBit("dat", 9, 1, 1);
        $this->frameSources[$this->frameNumber]["sort_flag"] = $this->getImageDataBit("dat", 9, 2, 1);
        $this->frameSources[$this->frameNumber]["color_table_size"] = (pow(2, ($this->getImageDataBit("dat", 9, 5, 3) + 1)) * 3);
        $this->frameSources[$this->frameNumber]["color_table"] = substr($this->frameSources[$this->frameNumber]["imagedata"], 10, $this->frameSources[$this->frameNumber]["color_table_size"]);
        $this->frameSources[$this->frameNumber]["lzw_code_size"] = ord($this->getImageDataByte("dat", 10, 1));

        $this->framePositions[$this->frameNumber] = [
            'x' => $this->frameSources[$this->frameNumber]["offset_left"],
            'y' => $this->frameSources[$this->frameNumber]["offset_top"],
        ];

        $this->frameDimensions[$this->frameNumber] = [
            'width' => $this->frameSources[$this->frameNumber]["width"],
            'height' => $this->frameSources[$this->frameNumber]["height"],
        ];

        // Decoding
        $this->orgvars[$this->frameNumber]["transparent_color_flag"] = $this->frameSources[$this->frameNumber]["transparent_color_flag"];
        $this->orgvars[$this->frameNumber]["transparent_color_index"] = $this->frameSources[$this->frameNumber]["transparent_color_index"];
        $this->orgvars[$this->frameNumber]["delay_time"] = $this->frameSources[$this->frameNumber]["delay_time"];
        $this->orgvars[$this->frameNumber]["disposal_method"] = $this->frameSources[$this->frameNumber]["disposal_method"];
        $this->orgvars[$this->frameNumber]["offset_left"] = $this->frameSources[$this->frameNumber]["offset_left"];
        $this->orgvars[$this->frameNumber]["offset_top"] = $this->frameSources[$this->frameNumber]["offset_top"];

        // Updating the max width
        if ($this->gifMaxWidth < $this->frameSources[$this->frameNumber]["width"]) {
            $this->gifMaxWidth = $this->frameSources[$this->frameNumber]["width"];
        }

        // Updating the max height
        if ($this->gifMaxHeight < $this->frameSources[$this->frameNumber]["height"]) {
            $this->gifMaxHeight = $this->frameSources[$this->frameNumber]["height"];
        }
    }

    /**
     * Get the image data byte (old: get_imagedata_byte)
     */
    private function getImageDataByte(string $type, int $start, int $length): string
    {
        if ($type == "ext") {
            return substr($this->frameSources[$this->frameNumber]["graphicsextension"], $start, $length);
        }

        // "dat"
        return substr($this->frameSources[$this->frameNumber]["imagedata"], $start, $length);
    }

    /**
     * Get the image data bit (old: get_imagedata_bit)
     */
    private function getImageDataBit(string $type, int $byteIndex, int $bitStart, int $bitLength): number
    {
        if ($type == "ext") {
            return $this->readBits(ord(substr($this->frameSources[$this->frameNumber]["graphicsextension"], $byteIndex, 1)), $bitStart, $bitLength);
        }

        // "dat"
        return $this->readBits(ord(substr($this->frameSources[$this->frameNumber]["imagedata"], $byteIndex, 1)), $bitStart, $bitLength);
    }

    /**
     * Return the value of 2 ASCII chars (old: dualbyteval)
     */
    private function dualByteVal(string $s): int
    {
        $i = (ord($s[1]) * 256 + ord($s[0]));

        return $i;
    }

    /**
     * Read the data stream (old: read_data_stream)
     */
    private function readDataStream(int $firstLength)
    {
        $this->pointerForward($firstLength);
        $length = $this->readByteInt();

        if ($length != 0) {
            while ($length != 0) {
                $this->pointerForward($length);
                $length = $this->readByteInt();
            }
        }
    }

    /**
     * Open the gif file (old: loadfile)
     */
    private function openFile(string $filename)
    {
        $this->handle = fopen($filename, "rb");
        $this->pointer = 0;

        $imageSize = getimagesize($filename);
        $this->gifWidth = $imageSize[0];
        $this->gifHeight = $imageSize[1];
    }

    /**
     * Close the read gif file (old: closefile)
     */
    private function closeFile()
    {
        fclose($this->handle);
        $this->handle = 0;
    }

    /**
     * Read the file from the beginning to $byteCount in binary (old: readbyte)
     */
    private function readByte(int $byteCount): string
    {
        $data = fread($this->handle, $byteCount);
        $this->pointer += $byteCount;

        return $data;
    }

    /**
     * Read a byte and return ASCII value (old: readbyte_int)
     */
    private function readByteInt(): int
    {
        $data = fread($this->handle, 1);
        $this->pointer++;

        return ord($data);
    }

    /**
     * Convert a $byte to decimal (old: readbits)
     */
    private function readBits(string $byte, int $start, int $length): number
    {
        $bin = str_pad(decbin($byte), 8, "0", STR_PAD_LEFT);
        $data = substr($bin, $start, $length);

        return bindec($data);
    }

    /**
     * Rewind the file pointer reader (old: p_rewind)
     */
    private function pointerRewind(int $length)
    {
        $this->pointer -= $length;
        fseek($this->handle, $this->pointer);
    }

    /**
     * Forward the file pointer reader (old: p_forward)
     */
    private function pointerForward(int $length)
    {
        $this->pointer += $length;
        fseek($this->handle, $this->pointer);
    }

    /**
     * Get a section of the data from $start to $start + $length (old: datapart)
     */
    private function dataPart(int $start, int $length): string
    {
        fseek($this->handle, $start);
        $data = fread($this->handle, $length);
        fseek($this->handle, $this->pointer);

        return $data;
    }

    /**
     * Check if a character if a byte (old: checkbyte)
     */
    private function checkByte(int $byte): bool
    {
        if (fgetc($this->handle) == chr($byte)) {
            fseek($this->handle, $this->pointer);
            return true;
        }

        fseek($this->handle, $this->pointer);

        return false;
    }

    /**
     * Check the end of the file (old: checkEOF)
     */
    private function checkEOF(): bool
    {
        if (fgetc($this->handle) === false) {
            return true;
        }

        fseek($this->handle, $this->pointer);

        return false;
    }

    /**
     * Reset and clear this current object
     */
    private function reset()
    {
        $this->gif = null;
        $this->totalDuration = $this->gifMaxHeight = $this->gifMaxWidth = $this->handle = $this->pointer = $this->frameNumber = 0;
        $this->frameDimensions = $this->framePositions = $this->frameImages = $this->frameDurations = $this->globaldata = $this->orgvars = $this->frames = $this->fileHeader = $this->frameSources = [];
    }

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


    /**
     * Get the total of all added frame duration
     */
    public function getTotalDuration(): int
    {
        return $this->totalDuration;
    }

    /**
     * Get the number of extracted frames
     */
    public function getFrameNumber(): int
    {
        return $this->frameNumber;
    }

    /**
     * Get the extracted frames (images and durations)
     */
    public function getFrames(): array
    {
        return $this->frames;
    }

    /**
     * Get the extracted frame positions
     */
    public function getFramePositions(): array
    {
        return $this->framePositions;
    }

    /**
     * Get the extracted frame dimensions
     */
    public function getFrameDimensions(): array
    {
        return $this->frameDimensions;
    }

    /**
     * Get the extracted frame images
     */
    public function getFrameImages(): array
    {
        return $this->frameImages;
    }

    /**
     * Get the extracted frame durations
     */
    public function getFrameDurations(): array
    {
        return $this->frameDurations;
    }
}