"""
Binance public WebSocket provider.

No API key required. Subscribes to:
- <symbol>@trade       → TradeEvent
- <symbol>@bookTicker  → QuoteEvent

Auto-reconnect with exponential backoff via tenacity.
"""
from __future__ import annotations

import asyncio
import json
import logging
from datetime import datetime, timezone
from typing import AsyncIterator

import websockets
from websockets.exceptions import ConnectionClosed

from app.config import settings
from app.domain.events import (
    Event,
    QuoteEvent,
    TradeEvent,
)
from app.providers import MarketDataProvider

logger = logging.getLogger(__name__)


def _ms_to_dt(ms: int | float | None) -> datetime | None:
    """Convert millisecond epoch to UTC datetime."""
    if ms is None:
        return None
    return datetime.fromtimestamp(ms / 1000.0, tz=timezone.utc)


class BinanceProvider(MarketDataProvider):
    """
    Binance public WebSocket streams.

    Connects to the combined stream endpoint and subscribes to
    trade + bookTicker channels for each symbol.
    """

    name = "binance"

    def __init__(self) -> None:
        self._ws: websockets.WebSocketClientProtocol | None = None
        self._symbols: list[str] = []
        self._connected = False
        self._reconnect_count = 0
        self._base_url = settings.binance_ws_url

    async def connect(self) -> None:
        """Establish WebSocket connection."""
        logger.info("binance.connecting", extra={"url": self._base_url})
        self._ws = await websockets.connect(
            self._base_url,
            ping_interval=20,
            ping_timeout=10,
            close_timeout=5,
        )
        self._connected = True
        logger.info("binance.connected")

    async def subscribe(self, symbols: list[str]) -> None:
        """Subscribe to trade + bookTicker for each symbol."""
        if not self._ws:
            raise RuntimeError("Not connected. Call connect() first.")

        self._symbols = [s.lower() for s in symbols]
        streams = []
        for sym in self._symbols:
            streams.append(f"{sym}@trade")
            streams.append(f"{sym}@bookTicker")

        subscribe_msg = {
            "method": "SUBSCRIBE",
            "params": streams,
            "id": 1,
        }
        await self._ws.send(json.dumps(subscribe_msg))
        logger.info(
            "binance.subscribed",
            extra={"symbols": self._symbols, "streams": len(streams)},
        )

    async def stream(self) -> AsyncIterator[Event]:
        """
        Yield domain events. Handles reconnect automatically.
        """
        backoff = settings.reconnect_base_delay

        while True:
            try:
                if not self._connected or not self._ws:
                    await self._reconnect(backoff)

                # Set timeout for heartbeat detection
                try:
                    raw = await asyncio.wait_for(
                        self._ws.recv(),  # type: ignore
                        timeout=settings.heartbeat_timeout,
                    )
                except asyncio.TimeoutError:
                    logger.warning(
                        "binance.heartbeat_timeout",
                        extra={"timeout": settings.heartbeat_timeout},
                    )
                    self._connected = False
                    continue

                # Reset backoff on successful message
                backoff = settings.reconnect_base_delay

                data = json.loads(raw)

                # Skip subscription confirmations
                if "result" in data and "id" in data:
                    continue

                event = self._parse(data)
                if event:
                    yield event

            except ConnectionClosed as e:
                logger.warning(
                    "binance.connection_closed",
                    extra={"code": e.code, "reason": str(e.reason)},
                )
                self._connected = False
                backoff = min(backoff * 2, settings.reconnect_max_delay)

            except Exception as e:
                logger.error("binance.stream_error", extra={"error": str(e)})
                self._connected = False
                backoff = min(backoff * 2, settings.reconnect_max_delay)

    async def _reconnect(self, delay: float) -> None:
        """Reconnect with delay, then resubscribe."""
        self._reconnect_count += 1
        logger.info(
            "binance.reconnecting",
            extra={"delay": delay, "attempt": self._reconnect_count},
        )
        await asyncio.sleep(delay)

        try:
            if self._ws:
                await self._ws.close()
        except Exception:
            pass

        await self.connect()
        if self._symbols:
            await self.subscribe(self._symbols)

    def _parse(self, data: dict) -> Event | None:
        """Parse raw Binance JSON into domain events."""
        event_type = data.get("e")

        if event_type == "trade":
            return self._parse_trade(data)
        elif event_type == "bookTicker" or ("b" in data and "a" in data and "s" in data and "e" not in data):
            # bookTicker doesn't always have "e" field in combined stream
            return self._parse_book_ticker(data)

        return None

    def _parse_trade(self, data: dict) -> TradeEvent:
        """
        Binance trade payload:
        {
          "e": "trade", "E": 1672515782136, "s": "BNBBTC",
          "t": 12345, "p": "0.001", "q": "100",
          "T": 1672515782136, "m": true
        }
        """
        return TradeEvent(
            provider=self.name,
            symbol=data.get("s", "").upper(),
            price=float(data.get("p", 0)),
            size=float(data.get("q", 0)),
            ts_exchange=_ms_to_dt(data.get("T")),
            side="sell" if data.get("m") else "buy",  # m=True → buyer is maker → trade is a sell
            trade_id=str(data.get("t", "")),
        )

    def _parse_book_ticker(self, data: dict) -> QuoteEvent:
        """
        Binance bookTicker payload:
        {
          "u": 400900217, "s": "BNBUSDT",
          "b": "25.35190000", "B": "31.21000000",
          "a": "25.36520000", "A": "40.66000000"
        }
        """
        return QuoteEvent(
            provider=self.name,
            symbol=data.get("s", "").upper(),
            bid=float(data.get("b", 0)),
            ask=float(data.get("a", 0)),
            bid_size=float(data.get("B", 0)),
            ask_size=float(data.get("A", 0)),
            ts_exchange=_ms_to_dt(data.get("E")),
        )

    async def close(self) -> None:
        """Close the WebSocket connection."""
        self._connected = False
        if self._ws:
            try:
                await self._ws.close()
            except Exception:
                pass
        logger.info(
            "binance.closed",
            extra={"reconnect_count": self._reconnect_count},
        )