from __future__ import annotations

import asyncio
import inspect
from collections.abc import Awaitable, Callable
from typing import Any, Protocol, TypeAlias, TypeVar, runtime_checkable

from google.protobuf.message import Message

from toki_socket.packets.message_common_pb2 import HeartBeat, PacketBase

T = TypeVar("T", bound=Message)
ParserMap: TypeAlias = dict[str, Callable[[bytes], Message]]
RequestHandler: TypeAlias = Callable[..., Message | Awaitable[Message | None] | None]

_STOP = object()
MAX_NONCE = 2_147_483_647


class NotConnectedError(RuntimeError):
    def __init__(self) -> None:
        super().__init__("not connected")


@runtime_checkable
class Transport(Protocol):
    async def write_packet(self, base: PacketBase) -> None: ...

    async def close(self) -> None: ...


class Communicator:
    def __init__(self) -> None:
        self._nonce = 0
        self._is_alive = False
        self._parser_map: ParserMap = {}
        self._handlers: dict[str, list[Callable[[Message], Any]]] = {}
        self._req_handlers: dict[str, RequestHandler] = {}
        self._pending_requests: dict[int, tuple[str, asyncio.Future[Message]]] = {}
        self._write_queue: asyncio.Queue[Any] = asyncio.Queue(maxsize=64)
        self._closed = asyncio.Event()
        self._transport: Transport | None = None
        self._write_loop_task: asyncio.Task[None] | None = None
        self._write_error_handler: Callable[[Exception], Any] | None = None

    def initialize(self, transport: Transport, parser_map: ParserMap) -> None:
        self._transport = transport
        self._parser_map = dict(parser_map)
        self._parser_map[type_name_of(HeartBeat)] = HeartBeat.FromString
        self._handlers = {}
        self._req_handlers = {}
        self._pending_requests = {}
        self._write_queue = asyncio.Queue(maxsize=64)
        self._closed = asyncio.Event()
        self._is_alive = True
        self._write_loop_task = asyncio.create_task(self._write_loop())

    def is_alive(self) -> bool:
        return self._is_alive

    def set_write_error_handler(self, fn: Callable[[Exception], Any]) -> None:
        self._write_error_handler = fn

    def next_nonce(self) -> int:
        if self._nonce >= MAX_NONCE:
            self._nonce = 0
        self._nonce += 1
        return self._nonce

    def shutdown(self) -> None:
        if not self._is_alive and self._closed.is_set():
            return
        self._is_alive = False
        self._closed.set()
        for _, pending in list(self._pending_requests.values()):
            if not pending.done():
                pending.set_exception(NotConnectedError())
        self._pending_requests.clear()
        try:
            self._write_queue.put_nowait(_STOP)
        except asyncio.QueueFull:
            if self._write_loop_task is not None:
                self._write_loop_task.cancel()

    async def close(self) -> None:
        self.shutdown()
        if self._transport is not None:
            await self._transport.close()

    async def wait_closed(self) -> None:
        await self._closed.wait()

    async def _write_loop(self) -> None:
        while True:
            item = await self._write_queue.get()
            if item is _STOP:
                return
            base, done = item
            try:
                if self._transport is None:
                    raise NotConnectedError()
                await self._transport.write_packet(base)
                if not done.done():
                    done.set_result(None)
            except Exception as exc:
                if not done.done():
                    done.set_exception(exc)
                if self._write_error_handler is not None:
                    self._write_error_handler(exc)

    async def queue_packet(self, base: PacketBase) -> None:
        if not self.is_alive():
            raise NotConnectedError()

        loop = asyncio.get_running_loop()
        done: asyncio.Future[None] = loop.create_future()
        item = (base, done)
        try:
            self._write_queue.put_nowait(item)
        except asyncio.QueueFull:
            closed_task = asyncio.create_task(self._closed.wait())
            put_task = asyncio.create_task(self._write_queue.put(item))
            finished, pending = await asyncio.wait(
                {closed_task, put_task},
                return_when=asyncio.FIRST_COMPLETED,
            )
            for task in pending:
                task.cancel()
            if closed_task in finished:
                raise NotConnectedError()

        closed_task = asyncio.create_task(self._closed.wait())
        finished, pending = await asyncio.wait(
            {done, closed_task},
            return_when=asyncio.FIRST_COMPLETED,
        )
        for task in pending:
            task.cancel()
        if closed_task in finished and not done.done():
            raise NotConnectedError()
        await done

    async def send(self, message: Message) -> None:
        if not self.is_alive():
            raise NotConnectedError()
        await self.queue_packet(
            PacketBase(
                typeName=type_name_of(message),
                nonce=self.next_nonce(),
                data=message.SerializeToString(),
            )
        )

    async def send_request(
        self,
        req: Message,
        res_type: type[T] | T,
        timeout: float = 30.0,
    ) -> T:
        if not self.is_alive():
            raise NotConnectedError()
        request_nonce = self.next_nonce()
        expected_type_name = type_name_of(res_type)
        loop = asyncio.get_running_loop()
        pending: asyncio.Future[Message] = loop.create_future()
        self._pending_requests[request_nonce] = (expected_type_name, pending)

        try:
            await self.queue_packet(
                PacketBase(
                    typeName=type_name_of(req),
                    nonce=request_nonce,
                    data=req.SerializeToString(),
                )
            )
            timeout = timeout if timeout > 0 else 30.0
            return await asyncio.wait_for(pending, timeout)
        except TimeoutError as exc:
            raise TimeoutError(f"request timeout for nonce {request_nonce}") from exc
        finally:
            self._pending_requests.pop(request_nonce, None)

    def add_listener(self, type_name: str, fn: Callable[[Message], Any]) -> None:
        if type_name in self._req_handlers:
            raise ValueError(f"type {type_name} is already registered with add_request_listener")
        self._handlers.setdefault(type_name, []).append(fn)

    def remove_listeners(self, type_name: str) -> None:
        self._handlers.pop(type_name, None)

    def add_request_listener(self, type_name: str, fn: RequestHandler) -> None:
        if self._handlers.get(type_name):
            raise ValueError(f"type {type_name} is already registered with add_listener")
        if type_name in self._req_handlers:
            raise ValueError(f"type {type_name} is already registered with add_request_listener")
        self._req_handlers[type_name] = fn

    def on_received_data(
        self,
        type_name: str,
        data: bytes,
        nonce: int = 0,
        response_nonce: int = 0,
    ) -> None:
        if response_nonce > 0:
            self._handle_response(type_name, data, response_nonce)
            return

        req_handler = self._req_handlers.get(type_name)
        listeners = list(self._handlers.get(type_name, []))

        if req_handler is not None:
            try:
                message = self._parse(type_name, data)
            except Exception:
                return
            asyncio.create_task(self._run_request_handler(req_handler, message, nonce))
            return

        if not listeners:
            return
        try:
            message = self._parse(type_name, data)
        except Exception:
            return
        for listener in listeners:
            listener(message)

    async def _run_request_handler(
        self,
        handler: RequestHandler,
        message: Message,
        request_nonce: int,
    ) -> None:
        try:
            result = handler(message, request_nonce) if _accepts_nonce(handler) else handler(message)
            if inspect.isawaitable(result):
                result = await result
            if result is None or not self.is_alive():
                return
            await self.queue_packet(
                PacketBase(
                    typeName=type_name_of(result),
                    nonce=self.next_nonce(),
                    responseNonce=request_nonce,
                    data=result.SerializeToString(),
                )
            )
        except Exception:
            return

    def _handle_response(self, type_name: str, data: bytes, response_nonce: int) -> None:
        item = self._pending_requests.pop(response_nonce, None)
        if item is None:
            return
        expected_type_name, pending = item
        if type_name != expected_type_name:
            pending.set_exception(
                ValueError(
                    f"response type mismatch for nonce {response_nonce}: "
                    f"expected {expected_type_name}, got {type_name}"
                )
            )
            return
        try:
            pending.set_result(self._parse(type_name, data))
        except Exception as exc:
            pending.set_exception(exc)

    def _parse(self, type_name: str, data: bytes) -> Message:
        parser = self._parser_map.get(type_name)
        if parser is None:
            raise ValueError(f"protobuf parser is not registered for type {type_name}")
        return parser(data)


def type_name_of(message_or_class: Message | type[Message]) -> str:
    descriptor = getattr(message_or_class, "DESCRIPTOR", None)
    if descriptor is None:
        descriptor = message_or_class.__class__.DESCRIPTOR
    return descriptor.name


def _accepts_nonce(handler: RequestHandler) -> bool:
    try:
        signature = inspect.signature(handler)
    except (TypeError, ValueError):
        return False
    positional = [
        param
        for param in signature.parameters.values()
        if param.kind
        in (inspect.Parameter.POSITIONAL_ONLY, inspect.Parameter.POSITIONAL_OR_KEYWORD)
    ]
    return len(positional) >= 2