<?php

namespace NoccyLabs\React\Http2\Frame;

abstract class Frame
{
    const FRAME_DATA = 0x0;
    const FRAME_HEADERS = 0x1;
    const FRAME_PRIORITY = 0x2;
    const FRAME_SETTINGS = 0x4;
    const FRAME_PUSH_PROMISE = 0x5;
    const FRAME_PING = 0x6;
    const FRAME_GOAWAY = 0x7;
    const FRAME_WINDOW_UPDATE = 0x8;
    const FRAME_CONTINUATION = 0x9;

    public static $frameMap = [
        self::FRAME_DATA => DataFrame::class,
        self::FRAME_HEADERS => HeadersFrame::class,
        self::FRAME_PRIORITY => PriorityFrame::class,
        self::FRAME_SETTINGS => SettingsFrame::class,
        self::FRAME_PUSH_PROMISE => PushPromiseFrame::class,
        self::FRAME_PING => PingFrame::class,
        self::FRAME_GOAWAY => GoAwayFrame::class,
        self::FRAME_WINDOW_UPDATE => WindowUpdateFrame::class,
        self::FRAME_CONTINUATION => ContinuationFrame::class
    ];

    /** @var int The associated condition is not a result of an error.  For example, a GOAWAY might include this code to indicate graceful shutdown of a connection. */
    const ERROR_NO_ERROR = 0x0; 
    /** @var int The endpoint detected an unspecific protocol error.  This error is for use when a more specific error code is not available. */
    const ERROR_PROTOCOL_ERROR = 0x1; 
    /** @var int The endpoint encountered an unexpected internal error. */
    const ERROR_INTERNAL_ERROR = 0x2; 
    /** @var int The endpoint detected that its peer violated the flow-control protocol. */
    const ERROR_FLOW_CONTROL_ERROR = 0x3; 
    /** @var int The endpoint sent a SETTINGS frame but did not receive a response in a timely manner.  See Section 6.5.3 ("Settings Synchronization"). */
    const ERROR_SETTINGS_TIMEOUT = 0x4; 
    /** @var int The endpoint received a frame after a stream was half-closed. */
    const ERROR_STREAM_CLOSED = 0x5; 
    /** @var int The endpoint received a frame with an invalid size. */
    const ERROR_FRAME_SIZE_ERROR = 0x6; 
    /** @var int The endpoint refused the stream prior to performing any application processing (see Section 8.1.4 for details). */
    const ERROR_REFUSED_STREAM = 0x7; 
    /** @var int Used by the endpoint to indicate that the stream is no longer needed. */
    const ERROR_CANCEL = 0x8; 
    /** @var int The endpoint is unable to maintain the header compression context for the connection. */
    const ERROR_COMPRESSION_ERROR = 0x9; 
    /** @var int The connection established in response to aCONNECT request (Section 8.3) was reset or abnormally closed. */
    const ERROR_CONNECT_ERROR = 0xa; 
    /** @var int The endpoint detected that its peer is exhibiting a behavior that might be generating excessive load. */
    const ERROR_ENHANCE_YOUR_CALM = 0xb; 
    /** @var int The underlying transport has properties that do not meet minimum security requirements (see Section 9.2). */
    const ERROR_INADEQUATE_SECURITY = 0xc; 
    /** @var int The endpoint requires that HTTP/1.1 be used instead of HTTP/2. */
    const ERROR_HTTP_1_1_REQUIRED = 0xd; 

    protected int $frameType;

    protected int $frameFlags;

    protected int $streamIdentifier;

    public function getFrameType(): int
    {
        return $this->frameType;
    }

    abstract public function toBinary(): string;

    abstract public function fromBinary(string $binary): void;

    public function encodeFrame(): string
    {
        $frame = '';

        // TODO build header
        $payload = $this->toBinary();
        $length = strlen($payload);
        $frame .= chr(($length >> 16) & 0xFF)
                . chr(($length >> 8) & 0xFF)
                . chr(($length) & 0xFF)
                . chr($this->frameType)
                . chr($this->frameFlags)
                . chr(($this->streamIdentifier >> 24) & 0x7F)
                . chr(($this->streamIdentifier >> 16) & 0xFF)
                . chr(($this->streamIdentifier >> 8) & 0xFF)
                . chr(($this->streamIdentifier) & 0xFF)
                . $payload;

        return $frame;
    }

    public static function parseFrame(string &$data): Frame
    {
        $header = array_map('ord', str_split(substr($data,0,9)));
        $length = ($header[0] << 16)
                | ($header[1] << 8)
                | ($header[2]);
        $type   = $header[3];
        $flags  = $header[4];
        $stream = (($header[5] & 0x7F) << 24)
                | ($header[6] << 16)
                | ($header[7] << 8)
                | ($header[8]);
        
        if (!array_key_exists($type, self::$frameMap)) {
            // TODO handle this
        }

        /** @var Frame $frame */
        $frame = new self::$frameMap[$type];
        $frame->frameType = $type;
        $frame->frameFlags = $flags;
        $frame->streamIdentifier = $stream;

        // Grab the payload and parse it
        $payload = substr($data, 9, $length);
        $frame->fromBinary($payload);

        return $frame;
    }

}