import argparse
import asyncio
import logging
import time

from aiortc import RTCIceCandidate, RTCPeerConnection, RTCSessionDescription
from aiortc.contrib.signaling import BYE, add_signaling_arguments, create_signaling

# optional, for better performance
try:
    import uvloop
except ImportError:
    uvloop = None


async def consume_signaling(pc, signaling):
    while True:
        obj = await signaling.receive()

        if isinstance(obj, RTCSessionDescription):
            await pc.setRemoteDescription(obj)

            if obj.type == "offer":
                # send answer
                await pc.setLocalDescription(await pc.createAnswer())
                await signaling.send(pc.localDescription)
        elif isinstance(obj, RTCIceCandidate):
            await pc.addIceCandidate(obj)
        elif obj is BYE:
            print("Exiting")
            break


async def run_answer(pc, signaling, fp):
    await signaling.connect()

    @pc.on("datachannel")
    def on_datachannel(channel):
        start = time.time()
        octets = 0

        @channel.on("message")
        async def on_message(message):
            nonlocal octets

            if message:
                octets += len(message)
                fp.write(message)
            else:
                elapsed = time.time() - start
                print(
                    "received %d bytes in %.1f s (%.3f Mbps)"
                    % (octets, elapsed, octets * 8 / elapsed / 1000000)
                )

                # say goodbye
                await signaling.send(BYE)

    await consume_signaling(pc, signaling)


async def run_offer(pc, signaling, fp):
    await signaling.connect()

    done_reading = False
    channel = pc.createDataChannel("filexfer")

    def send_data():
        nonlocal done_reading

        while (
            channel.bufferedAmount <= channel.bufferedAmountLowThreshold
        ) and not done_reading:
            data = fp.read(16384)
            channel.send(data)
            if not data:
                done_reading = True

    channel.on("bufferedamountlow", send_data)
    channel.on("open", send_data)

    # send offer
    await pc.setLocalDescription(await pc.createOffer())
    await signaling.send(pc.localDescription)

    await consume_signaling(pc, signaling)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Data channel file transfer")
    parser.add_argument("role", choices=["send", "receive"])
    parser.add_argument("filename")
    parser.add_argument("--verbose", "-v", action="count")
    add_signaling_arguments(parser)
    args = parser.parse_args()

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

    if uvloop is not None:
        asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())

    signaling = create_signaling(args)
    pc = RTCPeerConnection()
    if args.role == "send":
        fp = open(args.filename, "rb")
        coro = run_offer(pc, signaling, fp)
    else:
        fp = open(args.filename, "wb")
        coro = run_answer(pc, signaling, fp)

    # run event loop
    loop = asyncio.get_event_loop()
    try:
        loop.run_until_complete(coro)
    except KeyboardInterrupt:
        pass
    finally:
        fp.close()
        loop.run_until_complete(pc.close())
        loop.run_until_complete(signaling.close())