from __future__ import annotations

import asyncio
import contextlib
from dataclasses import dataclass
from typing import Awaitable, Callable, Dict

from .config import Config, RelayNode
from .protocol import AUTH, STATUS_OK, Frame, encode_json, read_frame, write_frame
from .scheduler import Scheduler

FrameHandler = Callable[["RelayConnection", Frame], Awaitable[None]]


@dataclass
class RelayConnection:
    node: RelayNode
    manager: "RelayManager"
    reader: asyncio.StreamReader
    writer: asyncio.StreamWriter
    closed: bool = False
    handlers: Dict[tuple[int, int], FrameHandler] = None
    pump_task: asyncio.Task | None = None

    def __post_init__(self) -> None:
        if self.handlers is None:
            self.handlers = {}

    async def start(self) -> None:
        print(f"[edge] connecting relay name={self.node.name} addr={self.node.host}:{self.node.port}")
        await write_frame(self.writer, Frame(AUTH, 0, 0, 0, 0, encode_json({"token": self.node.token})))
        frame = await read_frame(self.reader)
        if frame.kind != AUTH or frame.packet_id != STATUS_OK:
            raise ConnectionError(f"relay auth failed: {self.node.name}")
        print(f"[edge] relay connected name={self.node.name} addr={self.node.host}:{self.node.port}")
        self.pump_task = asyncio.create_task(self._pump())

    async def _pump(self) -> None:
        try:
            while True:
                frame = await read_frame(self.reader)
                handler = self.handlers.get((frame.session_id, frame.stream_id))
                if handler:
                    await handler(self, frame)
        except asyncio.IncompleteReadError:
            print(f"[edge] relay disconnected name={self.node.name} eof=true")
        except Exception as exc:
            print(f"[edge] relay pump error name={self.node.name} error={exc!r}")
        finally:
            await self.close()

    async def send(self, frame: Frame) -> None:
        if self.closed:
            raise ConnectionError(f"relay closed: {self.node.name}")
        await write_frame(self.writer, frame)

    def bind(self, session_id: int, stream_id: int, handler: FrameHandler) -> None:
        self.handlers[(session_id, stream_id)] = handler

    def unbind(self, session_id: int, stream_id: int) -> None:
        self.handlers.pop((session_id, stream_id), None)

    async def close(self) -> None:
        if self.closed:
            return
        self.closed = True
        self.manager.on_closed(self)
        self.writer.close()
        with contextlib.suppress(Exception):
            await self.writer.wait_closed()


class RelayManager:
    def __init__(self, config: Config) -> None:
        self.config = config
        self.scheduler = Scheduler(config)
        self.connections: Dict[str, RelayConnection] = {}
        self.tasks: list[asyncio.Task] = []

    async def start(self) -> None:
        await self.scheduler.start()
        for node in self.config.relays:
            self.tasks.append(asyncio.create_task(self._maintain(node)))

    async def _maintain(self, node: RelayNode) -> None:
        while True:
            if node.name in self.connections and not self.connections[node.name].closed:
                await asyncio.sleep(2)
                continue
            try:
                reader, writer = await asyncio.open_connection(node.host, node.port)
                connection = RelayConnection(node=node, manager=self, reader=reader, writer=writer)
                await connection.start()
                self.connections[node.name] = connection
                await connection.pump_task
            except Exception as exc:
                print(f"[edge] relay connect failed name={node.name} addr={node.host}:{node.port} error={exc!r}")
                await asyncio.sleep(3)

    def on_closed(self, connection: RelayConnection) -> None:
        current = self.connections.get(connection.node.name)
        if current is connection:
            self.connections.pop(connection.node.name, None)

    def available(self) -> list[RelayConnection]:
        chosen = {node.name for node in self.scheduler.choose()}
        preferred = [self.connections[name] for name in chosen if name in self.connections and not self.connections[name].closed]
        if preferred:
            return preferred
        return [conn for conn in self.connections.values() if not conn.closed]

    def snapshot(self) -> list[dict[str, object]]:
        data = self.scheduler.snapshot()
        online = {name for name, conn in self.connections.items() if not conn.closed}
        for item in data:
            item["online"] = item["name"] in online
        return data