from __future__ import annotations

import enum
import json
from collections.abc import AsyncIterator, Iterable
from typing import Any, cast

from starlette.requests import HTTPConnection, StateT
from starlette.responses import Response
from starlette.types import Message, Receive, Scope, Send


class WebSocketState(enum.Enum):
    CONNECTING = 0
    CONNECTED = 1
    DISCONNECTED = 2
    RESPONSE = 3


class WebSocketDisconnect(Exception):
    def __init__(self, code: int = 1000, reason: str | None = None) -> None:
        self.code = code
        self.reason = reason or ""


class WebSocket(HTTPConnection[StateT]):
    def __init__(self, scope: Scope, receive: Receive, send: Send) -> None:
        super().__init__(scope)
        assert scope["type"] == "websocket"
        self._receive = receive
        self._send = send
        self.client_state = WebSocketState.CONNECTING
        self.application_state = WebSocketState.CONNECTING

    async def receive(self) -> Message:
        """
        Receive ASGI websocket messages, ensuring valid state transitions.
        """
        if self.client_state == WebSocketState.CONNECTING:
            message = await self._receive()
            message_type = message["type"]
            if message_type != "websocket.connect":
                raise RuntimeError(f'Expected ASGI message "websocket.connect", but got {message_type!r}')
            self.client_state = WebSocketState.CONNECTED
            return message
        elif self.client_state == WebSocketState.CONNECTED:
            message = await self._receive()
            message_type = message["type"]
            if message_type not in {"websocket.receive", "websocket.disconnect"}:
                raise RuntimeError(
                    f'Expected ASGI message "websocket.receive" or "websocket.disconnect", but got {message_type!r}'
                )
            if message_type == "websocket.disconnect":
                self.client_state = WebSocketState.DISCONNECTED
            return message
        else:
            raise RuntimeError('Cannot call "receive" once a disconnect message has been received.')

    async def send(self, message: Message) -> None:
        """
        Send ASGI websocket messages, ensuring valid state transitions.
        """
        if self.application_state == WebSocketState.CONNECTING:
            message_type = message["type"]
            if message_type not in {"websocket.accept", "websocket.close", "websocket.http.response.start"}:
                raise RuntimeError(
                    'Expected ASGI message "websocket.accept", "websocket.close" or "websocket.http.response.start", '
                    f"but got {message_type!r}"
                )
            if message_type == "websocket.close":
                self.application_state = WebSocketState.DISCONNECTED
            elif message_type == "websocket.http.response.start":
                self.application_state = WebSocketState.RESPONSE
            else:
                self.application_state = WebSocketState.CONNECTED
            await self._send(message)
        elif self.application_state == WebSocketState.CONNECTED:
            message_type = message["type"]
            if message_type not in {"websocket.send", "websocket.close"}:
                raise RuntimeError(
                    f'Expected ASGI message "websocket.send" or "websocket.close", but got {message_type!r}'
                )
            if message_type == "websocket.close":
                self.application_state = WebSocketState.DISCONNECTED
            try:
                await self._send(message)
            except OSError:
                self.application_state = WebSocketState.DISCONNECTED
                raise WebSocketDisconnect(code=1006)
        elif self.application_state == WebSocketState.RESPONSE:
            message_type = message["type"]
            if message_type != "websocket.http.response.body":
                raise RuntimeError(f'Expected ASGI message "websocket.http.response.body", but got {message_type!r}')
            if not message.get("more_body", False):
                self.application_state = WebSocketState.DISCONNECTED
            await self._send(message)
        else:
            raise RuntimeError('Cannot call "send" once a close message has been sent.')

    async def accept(
        self,
        subprotocol: str | None = None,
        headers: Iterable[tuple[bytes, bytes]] | None = None,
    ) -> None:
        headers = headers or []

        if self.client_state == WebSocketState.CONNECTING:  # pragma: no branch
            # If we haven't yet seen the 'connect' message, then wait for it first.
            await self.receive()
        await self.send({"type": "websocket.accept", "subprotocol": subprotocol, "headers": headers})

    def _raise_on_disconnect(self, message: Message) -> None:
        if message["type"] == "websocket.disconnect":
            raise WebSocketDisconnect(message["code"], message.get("reason"))

    async def receive_text(self) -> str:
        if self.application_state != WebSocketState.CONNECTED:
            raise RuntimeError('WebSocket is not connected. Need to call "accept" first.')
        message = await self.receive()
        self._raise_on_disconnect(message)
        return cast(str, message["text"])

    async def receive_bytes(self) -> bytes:
        if self.application_state != WebSocketState.CONNECTED:
            raise RuntimeError('WebSocket is not connected. Need to call "accept" first.')
        message = await self.receive()
        self._raise_on_disconnect(message)
        return cast(bytes, message["bytes"])

    async def receive_json(self, mode: str = "text") -> Any:
        if mode not in {"text", "binary"}:
            raise RuntimeError('The "mode" argument should be "text" or "binary".')
        if self.application_state != WebSocketState.CONNECTED:
            raise RuntimeError('WebSocket is not connected. Need to call "accept" first.')
        message = await self.receive()
        self._raise_on_disconnect(message)

        if mode == "text":
            text = message["text"]
        else:
            text = message["bytes"].decode("utf-8")
        return json.loads(text)

    async def iter_text(self) -> AsyncIterator[str]:
        try:
            while True:
                yield await self.receive_text()
        except WebSocketDisconnect:
            pass

    async def iter_bytes(self) -> AsyncIterator[bytes]:
        try:
            while True:
                yield await self.receive_bytes()
        except WebSocketDisconnect:
            pass

    async def iter_json(self) -> AsyncIterator[Any]:
        try:
            while True:
                yield await self.receive_json()
        except WebSocketDisconnect:
            pass

    async def send_text(self, data: str) -> None:
        await self.send({"type": "websocket.send", "text": data})

    async def send_bytes(self, data: bytes) -> None:
        await self.send({"type": "websocket.send", "bytes": data})

    async def send_json(self, data: Any, mode: str = "text") -> None:
        if mode not in {"text", "binary"}:
            raise RuntimeError('The "mode" argument should be "text" or "binary".')
        text = json.dumps(data, separators=(",", ":"), ensure_ascii=False)
        if mode == "text":
            await self.send({"type": "websocket.send", "text": text})
        else:
            await self.send({"type": "websocket.send", "bytes": text.encode("utf-8")})

    async def close(self, code: int = 1000, reason: str | None = None) -> None:
        await self.send({"type": "websocket.close", "code": code, "reason": reason or ""})

    async def send_denial_response(self, response: Response) -> None:
        if "websocket.http.response" in self.scope.get("extensions", {}):
            await response(self.scope, self.receive, self.send)
        else:
            raise RuntimeError("The server doesn't support the Websocket Denial Response extension.")


class WebSocketClose:
    def __init__(self, code: int = 1000, reason: str | None = None) -> None:
        self.code = code
        self.reason = reason or ""

    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
        await send({"type": "websocket.close", "code": self.code, "reason": self.reason})
