import argparse
import asyncio
import json
import logging
import os
import platform
import ssl
from typing import Optional

from aiohttp import web
from aiortc import (
    MediaStreamTrack,
    RTCPeerConnection,
    RTCRtpSender,
    RTCSessionDescription,
)
from aiortc.contrib.media import MediaPlayer, MediaRelay

ROOT = os.path.dirname(__file__)

pcs = set()
relay = None
webcam = None


def create_local_tracks(
    play_from: str, decode: bool
) -> tuple[Optional[MediaStreamTrack], Optional[MediaStreamTrack]]:
    global relay, webcam

    if play_from:
        # If a file name was given, play from that file.
        player = MediaPlayer(play_from, decode=decode)
        return player.audio, player.video
    else:
        # Otherwise, play from the system's default webcam.
        #
        # In order to serve the same webcam to multiple users we make use of
        # a `MediaRelay`. The webcam will stay open, so it is our responsability
        # to stop the webcam when the application shuts down in `on_shutdown`.
        options = {"framerate": "30", "video_size": "640x480"}
        if relay is None:
            if platform.system() == "Darwin":
                webcam = MediaPlayer(
                    "default:none", format="avfoundation", options=options
                )
            elif platform.system() == "Windows":
                webcam = MediaPlayer(
                    "video=Integrated Camera", format="dshow", options=options
                )
            else:
                webcam = MediaPlayer("/dev/video0", format="v4l2", options=options)
            relay = MediaRelay()
        return None, relay.subscribe(webcam.video)


def force_codec(pc: RTCPeerConnection, sender: RTCRtpSender, forced_codec: str) -> None:
    kind = forced_codec.split("/")[0]
    codecs = RTCRtpSender.getCapabilities(kind).codecs
    transceiver = next(t for t in pc.getTransceivers() if t.sender == sender)
    transceiver.setCodecPreferences(
        [codec for codec in codecs if codec.mimeType == forced_codec]
    )


async def index(request: web.Request) -> web.Response:
    content = open(os.path.join(ROOT, "index.html"), "r").read()
    return web.Response(content_type="text/html", text=content)


async def javascript(request: web.Request) -> web.Response:
    content = open(os.path.join(ROOT, "client.js"), "r").read()
    return web.Response(content_type="application/javascript", text=content)


async def offer(request: web.Request) -> web.Response:
    params = await request.json()
    offer = RTCSessionDescription(sdp=params["sdp"], type=params["type"])

    pc = RTCPeerConnection()
    pcs.add(pc)

    @pc.on("connectionstatechange")
    async def on_connectionstatechange() -> None:
        print("Connection state is %s" % pc.connectionState)
        if pc.connectionState == "failed":
            await pc.close()
            pcs.discard(pc)

    # open media source
    audio, video = create_local_tracks(
        args.play_from, decode=not args.play_without_decoding
    )

    if audio:
        audio_sender = pc.addTrack(audio)
        if args.audio_codec:
            force_codec(pc, audio_sender, args.audio_codec)
        elif args.play_without_decoding:
            raise Exception("You must specify the audio codec using --audio-codec")

    if video:
        video_sender = pc.addTrack(video)
        if args.video_codec:
            force_codec(pc, video_sender, args.video_codec)
        elif args.play_without_decoding:
            raise Exception("You must specify the video codec using --video-codec")

    await pc.setRemoteDescription(offer)

    answer = await pc.createAnswer()
    await pc.setLocalDescription(answer)

    return web.Response(
        content_type="application/json",
        text=json.dumps(
            {"sdp": pc.localDescription.sdp, "type": pc.localDescription.type}
        ),
    )


async def on_shutdown(app: web.Application) -> None:
    # Close peer connections.
    coros = [pc.close() for pc in pcs]
    await asyncio.gather(*coros)
    pcs.clear()

    # If a shared webcam was opened, stop it.
    if webcam is not None:
        webcam.video.stop()


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="WebRTC webcam demo")
    parser.add_argument("--cert-file", help="SSL certificate file (for HTTPS)")
    parser.add_argument("--key-file", help="SSL key file (for HTTPS)")
    parser.add_argument("--play-from", help="Read the media from a file and sent it.")
    parser.add_argument(
        "--play-without-decoding",
        help=(
            "Read the media without decoding it (experimental). "
            "For now it only works with an MPEGTS container with only H.264 video."
        ),
        action="store_true",
    )
    parser.add_argument(
        "--host", default="0.0.0.0", help="Host for HTTP server (default: 0.0.0.0)"
    )
    parser.add_argument(
        "--port", type=int, default=8080, help="Port for HTTP server (default: 8080)"
    )
    parser.add_argument("--verbose", "-v", action="count")
    parser.add_argument(
        "--audio-codec", help="Force a specific audio codec (e.g. audio/opus)"
    )
    parser.add_argument(
        "--video-codec", help="Force a specific video codec (e.g. video/H264)"
    )

    args = parser.parse_args()

    if args.verbose:
        logging.basicConfig(level=logging.DEBUG)
    else:
        logging.basicConfig(level=logging.INFO)

    if args.cert_file:
        ssl_context = ssl.SSLContext()
        ssl_context.load_cert_chain(args.cert_file, args.key_file)
    else:
        ssl_context = None

    app = web.Application()
    app.on_shutdown.append(on_shutdown)
    app.router.add_get("/", index)
    app.router.add_get("/client.js", javascript)
    app.router.add_post("/offer", offer)
    web.run_app(app, host=args.host, port=args.port, ssl_context=ssl_context)