from __future__ import annotations

import asyncio
from collections.abc import Callable
from contextlib import suppress
from typing import Any

from app.backtest import Backtester
from app.broker import build_broker
from app.broker.base import Broker
from app.config import Settings
from app.engine.engine import TradingEngine
from app.engine.strategies import get_strategy
from app.market import build_market_data
from app.market.base import MarketData
from app.schemas import BacktestRequest, BacktestResult, StatusOut
from app.store import Store

FeedFactory = Callable[[Settings], MarketData]
BrokerFactory = Callable[[Settings], Broker]


class Runtime:
    """Owns the active engine and fans out live updates to WebSocket clients."""

    def __init__(
        self,
        settings: Settings,
        store: Store | None = None,
        *,
        feed_factory: FeedFactory = build_market_data,
        broker_factory: BrokerFactory = build_broker,
    ) -> None:
        self.settings = settings
        self.store = store or Store()
        self._feed_factory = feed_factory
        self._broker_factory = broker_factory
        self.engine: TradingEngine | None = None
        self._subscribers: set[asyncio.Queue] = set()

    # --- pub/sub ------------------------------------------------------
    def subscribe(self) -> asyncio.Queue:
        queue: asyncio.Queue = asyncio.Queue(maxsize=100)
        self._subscribers.add(queue)
        return queue

    def unsubscribe(self, queue: asyncio.Queue) -> None:
        self._subscribers.discard(queue)

    def _broadcast(self, payload: dict[str, Any]) -> None:
        for queue in list(self._subscribers):
            if queue.full():
                with suppress(asyncio.QueueEmpty):
                    queue.get_nowait()
            with suppress(asyncio.QueueFull):
                queue.put_nowait(payload)

    # --- lifecycle ----------------------------------------------------
    async def start(
        self,
        strategy_key: str,
        params: dict[str, Any] | None = None,
        *,
        symbol: str | None = None,
        timeframe: str | None = None,
        starting_balance: float | None = None,
    ) -> StatusOut:
        if self.engine is not None and self.engine.running:
            await self.stop()
        engine = TradingEngine(
            feed=self._feed_factory(self.settings),
            broker=self._broker_factory(self.settings),
            store=self.store,
            settings=self.settings,
        )
        engine.set_publisher(self._broadcast)
        self.engine = engine
        await engine.start(
            strategy_key,
            params,
            symbol=symbol,
            timeframe=timeframe,
            starting_balance=starting_balance,
        )
        return engine.status()

    async def stop(self) -> StatusOut:
        if self.engine is not None:
            await self.engine.stop()
            return self.engine.status()
        return self._idle_status()

    async def run_backtest(self, request: BacktestRequest) -> BacktestResult:
        symbol = request.symbol or self.settings.symbol
        timeframe = request.timeframe or self.settings.timeframe
        strategy_cls = get_strategy(request.strategy_key)
        strategy = strategy_cls(request.params)

        feed = self._feed_factory(self.settings)
        try:
            candles = await feed.fetch_candles(symbol, timeframe, request.limit)
        finally:
            await feed.close()

        backtester = Backtester(
            fee_bps=self.settings.fee_bps,
            slippage_bps=self.settings.slippage_bps,
            starting_balance=request.starting_balance or self.settings.starting_balance,
        )
        return backtester.run(candles, strategy, symbol, timeframe)

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

    def status(self) -> StatusOut:
        if self.engine is not None:
            return self.engine.status()
        return self._idle_status()

    def _idle_status(self) -> StatusOut:
        return StatusOut(
            running=False,
            mode=self.settings.mode,
            exchange=self.settings.exchange,
            symbol=self.settings.symbol,
            timeframe=self.settings.timeframe,
            strategy_key=None,
            strategy_name=None,
            params={},
            price=None,
            cash=self.settings.starting_balance,
            equity=self.settings.starting_balance,
            starting_balance=self.settings.starting_balance,
            realized_pnl=0.0,
            unrealized_pnl=0.0,
            total_pnl=0.0,
            open_positions=0,
            last_tick=None,
        )