from __future__ import annotations

import asyncio
from collections.abc import Callable

from app.broker import build_broker
from app.broker.base import Broker
from app.config import Settings
from app.engine.engine import Publish, 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 (
    MultiStatusOut,
    StartManyRequest,
    StrategySpec,
    StrategyStatusOut,
)
from app.store import Store

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


def normalise_weights(specs: list[StrategySpec]) -> list[float]:
    """Turn relative weights into allocations that sum to exactly 1.0."""
    total = sum(max(0.0, spec.weight) for spec in specs)
    if total <= 0:
        return [1 / len(specs)] * len(specs)
    return [max(0.0, spec.weight) / total for spec in specs]


class StrategyRun:
    """One strategy's engine plus the allocation it was given."""

    def __init__(self, spec: StrategySpec, engine: TradingEngine, allocation: float) -> None:
        self.spec = spec
        self.engine = engine
        self.allocation = allocation

    @property
    def key(self) -> str:
        return self.spec.strategy_key


class MultiStrategyManager:
    """Runs several strategies concurrently, each on its own capital slice.

    Every strategy gets an independent :class:`TradingEngine` seeded with
    ``starting_balance * allocation``, so one strategy's losses cannot eat into
    another's capital. Risk limits apply per strategy (each engine owns its own
    RiskManager); the manager aggregates status and can halt everything at once.
    """

    def __init__(
        self,
        *,
        store: Store,
        settings: Settings,
        feed_factory: FeedFactory = build_market_data,
        broker_factory: BrokerFactory = build_broker,
    ) -> None:
        self.store = store
        self.settings = settings
        self._feed_factory = feed_factory
        self._broker_factory = broker_factory
        self.runs: list[StrategyRun] = []
        self.starting_balance = settings.starting_balance
        self._publish_cb: Publish | None = None
        self._task: asyncio.Task | None = None

    def set_publisher(self, publish: Publish | None) -> None:
        self._publish_cb = publish

    @property
    def running(self) -> bool:
        return bool(self.runs) and any(run.engine.running for run in self.runs)

    @property
    def last_price(self) -> float | None:
        for run in self.runs:
            if run.engine.last_price is not None:
                return run.engine.last_price
        return None

    async def start(self, request: StartManyRequest) -> MultiStatusOut:
        await self.stop()

        starting_balance = float(request.starting_balance or self.settings.starting_balance)
        allocations = normalise_weights(request.strategies)
        self.starting_balance = starting_balance
        self.runs = []

        for spec, allocation in zip(request.strategies, allocations, strict=True):
            strategy_cls = get_strategy(spec.strategy_key)
            # Validate params early so a bad request fails before any orders.
            strategy_cls(spec.params)

            engine = TradingEngine(
                feed=self._feed_factory(self.settings),
                broker=self._broker_factory(self.settings),
                store=self.store,
                settings=self.settings,
            )
            engine.set_publisher(self._publish_cb)
            await engine.start(
                spec.strategy_key,
                spec.params,
                symbol=spec.symbol,
                timeframe=spec.timeframe,
                starting_balance=starting_balance * allocation,
            )
            self.runs.append(StrategyRun(spec, engine, allocation))

        return self.status()

    async def stop(self) -> MultiStatusOut:
        for run in self.runs:
            await run.engine.stop()
        self.runs = []
        return self.status()

    async def kill(self, reason: str = "manual kill switch") -> MultiStatusOut:
        for run in self.runs:
            await run.engine.kill(reason)
        return self.status()

    async def shutdown(self) -> None:
        for run in self.runs:
            await run.engine.shutdown()
        self.runs = []

    def status(self) -> MultiStatusOut:
        total_equity = 0.0
        per_strategy: list[StrategyStatusOut] = []
        last_tick = None
        for run in self.runs:
            engine_status = run.engine.status()
            total_equity += engine_status.equity
            if engine_status.last_tick and (
                last_tick is None or engine_status.last_tick > last_tick
            ):
                last_tick = engine_status.last_tick
            per_strategy.append(
                StrategyStatusOut(
                    strategy_key=engine_status.strategy_key or run.key,
                    strategy_name=engine_status.strategy_name,
                    params=engine_status.params,
                    symbol=engine_status.symbol,
                    timeframe=engine_status.timeframe,
                    allocation=run.allocation,
                    cash=engine_status.cash,
                    equity=engine_status.equity,
                    realized_pnl=engine_status.realized_pnl,
                    unrealized_pnl=engine_status.unrealized_pnl,
                    total_pnl=engine_status.total_pnl,
                    open_positions=engine_status.open_positions,
                    halted=engine_status.halted,
                    halt_reason=engine_status.halt_reason,
                    trades_today=engine_status.trades_today,
                    day_pnl=engine_status.day_pnl,
                    drawdown_pct=engine_status.drawdown_pct,
                    error=engine_status.error,
                )
            )

        return MultiStatusOut(
            running=self.running,
            mode=self.settings.mode,
            exchange=self.settings.exchange,
            price=self.last_price,
            starting_balance=self.starting_balance,
            equity=total_equity,
            total_pnl=total_equity - self.starting_balance,
            strategies=per_strategy,
            last_tick=last_tick,
        )

    def engine_at(self, index: int) -> TradingEngine | None:
        if 0 <= index < len(self.runs):
            return self.runs[index].engine
        return None


__all__ = ["MultiStrategyManager", "StrategyRun", "normalise_weights"]