from __future__ import annotations

import asyncio
import contextlib
import json
import random
import socket
from dataclasses import dataclass
import time
from typing import Awaitable, Callable, Dict

from .config_udp import UdpConfig, UdpRelayNode
from .logging_utils import log_print as print
from .protocol import AUTH, PING, PONG, STATUS_OK, TCP_CLOSE, Frame, encode_json, read_frame, write_frame
from .scheduler_udp import UdpScheduler

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


@dataclass
class UdpRelayConnection:
    node: UdpRelayNode
    manager: "UdpRelayManager"
    reader: asyncio.StreamReader
    writer: asyncio.StreamWriter
    closed: bool = False
    handlers: Dict[tuple[int, int], FrameHandler] = None
    dispatch_tasks: Dict[tuple[int, int], asyncio.Task] = None
    pump_task: asyncio.Task | None = None
    keepalive_task: asyncio.Task | None = None
    last_pong_at: float = 0.0
    send_lock: asyncio.Lock | None = None
    closed_event: asyncio.Event | None = None
    dropped_frames: Dict[int, int] = None
    dropped_report_task: asyncio.Task | None = None
    def __post_init__(self) -> None:
        if self.handlers is None:
            self.handlers = {}
        if self.dispatch_tasks is None:
            self.dispatch_tasks = {}
        if self.send_lock is None:
            self.send_lock = asyncio.Lock()
        if self.closed_event is None:
            self.closed_event = asyncio.Event()
        if self.dropped_frames is None:
            self.dropped_frames = {}

    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}")
        if frame.payload:
            with contextlib.suppress(Exception):
                json.loads(frame.payload.decode("utf-8"))
        self.last_pong_at = time.monotonic()
        self.keepalive_task = asyncio.create_task(self._keepalive())
        self.pump_task = asyncio.create_task(self._pump())
        print(f"[edge] relay connected name={self.node.name} addr={self.node.host}:{self.node.port} mode=udp")

    async def _keepalive(self) -> None:
        try:
            while not self.closed:
                await asyncio.sleep(self.manager.config.relay_ping_interval)
                if self.closed:
                    break
                if self.last_pong_at and time.monotonic() - self.last_pong_at > (self.manager.config.relay_ping_interval + self.manager.config.relay_ping_timeout):
                    print(f"[edge] relay health timeout name={self.node.name} addr={self.node.host}:{self.node.port} timeout={self.manager.config.relay_ping_timeout}")
                    await self.close()
                    break
                await self.send(Frame(PING, 0, 0, 0, 0, b""))
        except asyncio.CancelledError:
            pass
        except Exception:
            await self.close()

    async def _pump(self) -> None:
        try:
            while True:
                frame = await read_frame(self.reader)
                if frame.kind == PONG:
                    self.last_pong_at = time.monotonic()
                    continue
                handler = self.handlers.get((frame.session_id, frame.stream_id))
                if handler:
                    self._dispatch_frame(frame, handler)
                else:
                    self._record_dropped_frame(frame.kind)
        except (asyncio.IncompleteReadError, ConnectionResetError, BrokenPipeError, OSError):
            pass
        except Exception:
            pass
        finally:
            await self.close()

    def _dispatch_frame(self, frame: Frame, handler: FrameHandler) -> None:
        key = (frame.session_id, frame.stream_id)
        previous = self.dispatch_tasks.get(key)
        task = asyncio.create_task(self._run_handler(key, frame, handler, previous))
        self.dispatch_tasks[key] = task

    async def _run_handler(self, key: tuple[int, int], frame: Frame, handler: FrameHandler, previous: asyncio.Task | None) -> None:
        try:
            if previous is not None:
                with contextlib.suppress(Exception):
                    await previous
            if self.closed:
                return
            await handler(self, frame)
        except asyncio.CancelledError:
            pass
        except Exception:
            if not self.closed:
                await self.close()
        finally:
            if self.dispatch_tasks.get(key) is asyncio.current_task():
                self.dispatch_tasks.pop(key, None)

    def _record_dropped_frame(self, kind: int) -> None:
        self.dropped_frames[kind] = self.dropped_frames.get(kind, 0) + 1
        if self.dropped_report_task is None or self.dropped_report_task.done():
            self.dropped_report_task = asyncio.create_task(self._report_dropped_frames())

    async def _report_dropped_frames(self) -> None:
        try:
            await asyncio.sleep(5)
            dropped = self.dropped_frames
            self.dropped_frames = {}
            if dropped:
                detail = ", ".join(f"kind={kind} count={count}" for kind, count in sorted(dropped.items()))
                print(f"[edge] relay frame dropped summary name={self.node.name} {detail}")
        except asyncio.CancelledError:
            pass

    async def send(self, frame: Frame) -> None:
        if self.closed:
            raise ConnectionError(f"relay closed: {self.node.name}")
        assert self.send_lock is not None
        async with self.send_lock:
            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)
        task = self.dispatch_tasks.pop((session_id, stream_id), None)
        if task is not None:
            task.cancel()

    async def close(self) -> None:
        if self.closed:
            return
        self.closed = True
        assert self.closed_event is not None
        self.closed_event.set()
        handlers = list(self.handlers.items())
        self.handlers.clear()
        dispatch_tasks = list(self.dispatch_tasks.values())
        self.dispatch_tasks.clear()
        self.manager.on_closed(self)
        for (session_id, stream_id), handler in handlers:
            with contextlib.suppress(Exception):
                await handler(self, Frame(TCP_CLOSE, session_id, stream_id, 0, 0, b""))
        for task in dispatch_tasks:
            task.cancel()
        for task in dispatch_tasks:
            with contextlib.suppress(Exception):
                await task
        if self.dropped_report_task and self.dropped_report_task is not asyncio.current_task():
            self.dropped_report_task.cancel()
            with contextlib.suppress(Exception):
                await self.dropped_report_task
        if self.pump_task and self.pump_task is not asyncio.current_task():
            self.pump_task.cancel()
            with contextlib.suppress(Exception):
                await self.pump_task
        if self.keepalive_task and self.keepalive_task is not asyncio.current_task():
            self.keepalive_task.cancel()
            with contextlib.suppress(Exception):
                await self.keepalive_task
        self.writer.close()
        with contextlib.suppress(Exception):
            await self.writer.wait_closed()


class UdpRelayManager:
    def __init__(self, config: UdpConfig) -> None:
        self.config = config
        self.scheduler = UdpScheduler(config)
        self.connections: Dict[str, UdpRelayConnection] = {}
        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: UdpRelayNode) -> None:
        backoff = self.config.relay_reconnect_delay
        while True:
            current = self.connections.get(node.name)
            if current is not None and not current.closed:
                assert current.closed_event is not None
                await current.closed_event.wait()
                continue
            attempt = 1
            while True:
                try:
                    print(f"[edge] relay reconnect attempt name={node.name} addr={node.host}:{node.port} attempt={attempt} backoff={backoff:.1f}s")
                    reader, writer = await asyncio.wait_for(asyncio.open_connection(node.host, node.port), timeout=self.config.relay_open_timeout)
                    connection = UdpRelayConnection(node=node, manager=self, reader=reader, writer=writer)
                    sock = writer.get_extra_info("socket")
                    if sock is not None and self.config.relay_tcp_nodelay:
                        with contextlib.suppress(OSError):
                            sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
                    await connection.start()
                    self.connections[node.name] = connection
                    backoff = self.config.relay_reconnect_delay
                    assert connection.closed_event is not None
                    await connection.closed_event.wait()
                    print(f"[edge] relay supervisor noticed close name={node.name} addr={node.host}:{node.port}")
                    break
                except asyncio.CancelledError:
                    raise
                except Exception as exc:
                    print(f"[edge] relay connect failed name={node.name} addr={node.host}:{node.port} attempt={attempt} error={exc!r}")
                    jitter = random.uniform(0, min(1.0, backoff * 0.2))
                    await asyncio.sleep(backoff + jitter)
                    backoff = min(self.config.relay_reconnect_max_delay, max(self.config.relay_reconnect_delay, backoff * 2))
                    attempt += 1

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

    def available_udp(self) -> list[UdpRelayConnection]:
        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