import asyncio
import copy
from pathlib import Path
import pickle
import subprocess
import typing as tp
import warnings

import google.protobuf
from multiaddr import Multiaddr
import p2pclient
from libp2p.peer.id import ID

from hivemind.utils.networking import find_open_port


class P2PContext(object):
    def __init__(self, ours_id, ours_port, handle_name):
        self.peer_id = None
        self.peer_addr = None
        self.ours_id = ours_id
        self.ours_port = ours_port
        self.handle_name = handle_name


class P2P(object):
    """
    Forks a child process and executes p2pd command with given arguments.
    Can be used for peer to peer communication and procedure calls.
    Sends SIGKILL to the child in destructor.
    """

    P2PD_RELATIVE_PATH = 'hivemind_cli/p2pd'
    NUM_RETRIES = 3
    RETRY_DELAY = 0.4
    HEADER_LEN = 8
    BYTEORDER = 'big'

    class IncompleteRead(Exception):
        pass

    class InterruptedError(Exception):
        pass

    def __init__(self):
        self._child = None
        self._listen_task = None
        self._server_stopped = asyncio.Event()

    @classmethod
    async def create(cls, *args, quic=1, tls=1, conn_manager=1, dht_client=1,
                     nat_port_map=True, auto_nat=True, bootstrap=True,
                     host_port: int = None, daemon_listen_port: int = None, **kwargs):
        self = cls()
        p2pd_path = Path(__file__).resolve().parents[1] / P2P.P2PD_RELATIVE_PATH
        proc_args = self._make_process_args(
            str(p2pd_path), *args,
            quic=quic, tls=tls, connManager=conn_manager,
            dhtClient=dht_client, natPortMap=nat_port_map,
            autonat=auto_nat, b=bootstrap, **kwargs)
        self._assign_daemon_ports(host_port, daemon_listen_port)
        for try_count in range(self.NUM_RETRIES):
            try:
                self._initialize(proc_args)
                await self._identify_client(P2P.RETRY_DELAY * (2 ** try_count))
            except Exception as exc:
                warnings.warn("Failed to initialize p2p daemon: " + str(exc), RuntimeWarning)
                self._kill_child()
                if try_count == P2P.NUM_RETRIES - 1:
                    raise
                self._assign_daemon_ports()
                continue
            break
        return self

    def _initialize(self, proc_args: tp.List[str]) -> None:
        proc_args = copy.deepcopy(proc_args)
        proc_args.extend(self._make_process_args(
            hostAddrs=f'/ip4/0.0.0.0/tcp/{self._host_port},/ip4/0.0.0.0/udp/{self._host_port}/quic',
            listen=f'/ip4/127.0.0.1/tcp/{self._daemon_listen_port}'
        ))
        self._child = subprocess.Popen(
            args=proc_args,
            stdin=subprocess.PIPE, stdout=subprocess.PIPE,
            stderr=subprocess.PIPE, encoding="utf8"
        )
        self._client_listen_port = find_open_port()
        self._client = p2pclient.Client(
            Multiaddr(f'/ip4/127.0.0.1/tcp/{self._daemon_listen_port}'),
            Multiaddr(f'/ip4/127.0.0.1/tcp/{self._client_listen_port}'))

    async def _identify_client(self, delay):
        await asyncio.sleep(delay)
        encoded = await self._client.identify()
        self.id = encoded[0].to_base58()

    def _assign_daemon_ports(self, host_port=None, daemon_listen_port=None):
        self._host_port, self._daemon_listen_port = host_port, daemon_listen_port
        if host_port is None:
            self._host_port = find_open_port()
        if daemon_listen_port is None:
            self._daemon_listen_port = find_open_port()
            while self._daemon_listen_port == self._host_port:
                self._daemon_listen_port = find_open_port()

    @staticmethod
    async def send_raw_data(byte_str, stream):
        request = len(byte_str).to_bytes(P2P.HEADER_LEN, P2P.BYTEORDER) + byte_str
        await stream.send_all(request)

    @staticmethod
    async def send_data(data, stream):
        await P2P.send_raw_data(pickle.dumps(data), stream)

    @staticmethod
    async def send_protobuf(protobuf, out_proto_type, stream):
        if type(protobuf) != out_proto_type:
            error = TypeError('Unary handler returned protobuf of wrong type.')
            await P2P.send_raw_data(pickle.dumps(error), stream)
            raise error
        await P2P.send_raw_data(protobuf.SerializeToString(), stream)

    @staticmethod
    async def receive_exactly(stream, n_bytes, max_bytes=1 << 16):
        buffer = bytearray()
        while len(buffer) < n_bytes:
            data = await stream.receive_some(min(max_bytes, n_bytes - len(buffer)))
            if len(data) == 0:
                raise P2P.IncompleteRead()
            buffer.extend(data)
        return bytes(buffer)

    @staticmethod
    async def receive_raw_data(stream):
        header = await P2P.receive_exactly(stream, P2P.HEADER_LEN)
        content_length = int.from_bytes(header, P2P.BYTEORDER)
        data = await P2P.receive_exactly(stream, content_length)
        return data

    @staticmethod
    async def receive_data(stream):
        return pickle.loads(await P2P.receive_raw_data(stream))

    @staticmethod
    async def receive_protobuf(in_proto_type, stream):
        protobuf = in_proto_type()
        protobuf.ParseFromString(await P2P.receive_raw_data(stream))
        return protobuf

    @staticmethod
    def _handle_stream(handle):
        async def do_handle_stream(stream_info, stream):
            try:
                request = await P2P.receive_data(stream)
            except P2P.IncompleteRead:
                warnings.warn("Incomplete read while receiving request from peer", RuntimeWarning)
                await stream.close()
                return
            try:
                result = handle(request)
                await P2P.send_data(result, stream)
            except Exception as exc:
                await P2P.send_data(exc, stream)
            finally:
                await stream.close()

        return do_handle_stream

    @staticmethod
    def _handle_unary_stream(handle, context, in_proto_type, out_proto_type):
        async def watchdog(stream):
            await stream.receive_some(max_bytes=1)
            raise P2P.InterruptedError()

        async def do_handle_unary_stream(stream_info, stream):
            try:
                try:
                    request = await P2P.receive_protobuf(in_proto_type, stream)
                except P2P.IncompleteRead:
                    warnings.warn("Incomplete read while receiving request from peer",
                                  RuntimeWarning)
                    return
                except google.protobuf.message.DecodeError as error:
                    warnings.warn(repr(error), RuntimeWarning)
                    return

                context.peer_id, context.peer_addr = stream_info.peer_id, stream_info.addr
                done, pending = await asyncio.wait([watchdog(stream), handle(request, context)],
                                                   return_when=asyncio.FIRST_COMPLETED)
                try:
                    result = done.pop().result()
                    await P2P.send_protobuf(result, out_proto_type, stream)
                except P2P.InterruptedError:
                    pass
                except Exception as exc:
                    await P2P.send_data(exc, stream)
                finally:
                    pending_task = pending.pop()
                    pending_task.cancel()
                    try:
                        await pending_task
                    except asyncio.CancelledError:
                        pass
            finally:
                await stream.close()

        return do_handle_unary_stream

    def start_listening(self):
        async def listen():
            async with self._client.listen():
                await self._server_stopped.wait()

        self._listen_task = asyncio.create_task(listen())

    async def stop_listening(self):
        if self._listen_task is not None:
            self._server_stopped.set()
            self._listen_task.cancel()
            try:
                await self._listen_task
            except asyncio.CancelledError:
                self._listen_task = None
                self._server_stopped.clear()

    async def add_stream_handler(self, name, handle):
        if self._listen_task is None:
            self.start_listening()
        await self._client.stream_handler(name, P2P._handle_stream(handle))

    async def add_unary_handler(self, name, handle, in_proto_type, out_proto_type):
        if self._listen_task is None:
            self.start_listening()
        context = P2PContext(ours_id=self.id, ours_port=self._host_port, handle_name=name)
        await self._client.stream_handler(
            name, P2P._handle_unary_stream(handle, context, in_proto_type, out_proto_type))

    async def call_peer_handler(self, peer_id, handler_name, input_data):
        libp2p_peer_id = ID.from_base58(peer_id)
        stream_info, stream = await self._client.stream_open(libp2p_peer_id, (handler_name,))
        try:
            await P2P.send_data(input_data, stream)
            return await P2P.receive_data(stream)
        finally:
            await stream.close()

    def __del__(self):
        self._kill_child()

    def _kill_child(self):
        if self._child is not None and self._child.poll() is None:
            self._child.kill()
            self._child.wait()

    def _make_process_args(self, *args, **kwargs) -> tp.List[str]:
        proc_args = []
        proc_args.extend(
            str(entry) for entry in args
        )
        proc_args.extend(
            f'-{key}={value}' if value is not None else f'-{key}'
            for key, value in kwargs.items()
        )
        return proc_args