"""
Risk gate — final hard stop before venue execution.

The planner is not trusted. The optimiser is not trusted, the exchange adapter
is not trusted. This gate enforces hard invariants.
"""
from __future__ import annotations

import time
from collections import defaultdict
from typing import Deque
from collections import deque

from malkhut.actions import FulfilmentAction, PlannedPolicy, RiskDecision
from malkhut.state import (
    ActionKind,
    FulfilmentPolicyParams,
    MarketWorldState,
    MAX_ACCOUNT_LEVERAGE,
    MAX_CANCELS_PER_SYMBOL_PER_MINUTE,
    MAX_SYMBOL_NOTIONAL_FRACTION,
    Side,
)
from malkhut.cwm import materialize_price_from_action


class RiskGate:
    def __init__(self) -> None:
        self._kill_switch: bool = False
        self._cancel_timestamps: dict[str, Deque[float]] = defaultdict(
            lambda: deque(maxlen=MAX_CANCELS_PER_SYMBOL_PER_MINUTE + 10)
        )

    def set_kill_switch(self, active: bool) -> None:
        """Operator-controlled emergency stop."""
        self._kill_switch = active

    def record_cancel(self, symbol: str) -> None:
        """Record a cancel event for rate-limit tracking."""
        self._cancel_timestamps[symbol].append(time.time())

    def validate(
        self,
        state: MarketWorldState,
        planned: PlannedPolicy,
        params: FulfilmentPolicyParams,
        daat_verdict: str = "KNOWN",
    ) -> RiskDecision:
        """Validate a planned action.

        Args:
            daat_verdict: "KNOWN" | "MARGINAL" | "OUT_OF_DISTRIBUTION"
                From DAAT classifier. If OUT_OF_DISTRIBUTION, veto the action
                and fall back to doctrinal simple policy.
        """
        action = planned.selected_action

        if daat_verdict == "OUT_OF_DISTRIBUTION":
            return RiskDecision(True, None, "ood_veto_fall_back_to_doctrinal")

        if action.kind == ActionKind.NOOP:
            return RiskDecision(True, action, "noop")

        if self._kill_switch_active():
            return RiskDecision(False, None, "kill_switch")

        if self._cancel_rate_would_exceed(state, action):
            return RiskDecision(False, None, "cancel_rate_limit")

        if self._would_self_trade(state, action):
            return RiskDecision(False, None, "self_trade_risk")

        if self._would_exceed_leverage(state, action, params):
            return RiskDecision(False, None, "leverage_limit")

        if self._would_exceed_symbol_notional(state, action, params):
            return RiskDecision(False, None, "symbol_notional_limit")

        if self._post_only_would_cross(state, action):
            return RiskDecision(False, None, "post_only_cross")

        if self._violates_venue_minima(state, action):
            return RiskDecision(False, None, "venue_minimum")

        return RiskDecision(True, action, "approved")

    def _kill_switch_active(self) -> bool:
        return self._kill_switch

    def _cancel_rate_would_exceed(self, state: MarketWorldState, action: FulfilmentAction) -> bool:
        if action.kind != ActionKind.CANCEL and action.kind != ActionKind.CANCEL_REPLACE:
            return False
        symbol = state.venue.symbol
        now = time.time()
        window = self._cancel_timestamps[symbol]
        cutoff = now - 60.0
        while window and window[0] < cutoff:
            window.popleft()
        return len(window) >= MAX_CANCELS_PER_SYMBOL_PER_MINUTE

    def _would_self_trade(self, state: MarketWorldState, action: FulfilmentAction) -> bool:
        if action.kind not in (ActionKind.PLACE, ActionKind.CANCEL_REPLACE, ActionKind.CROSS_SPREAD):
            return False
        if action.side is None:
            return False
        for oo in state.open_orders:
            if oo.symbol != state.venue.symbol:
                continue
            if oo.side != action.side:
                continue
            if oo.client_order_id == action.cancel_order_id:
                continue
            if oo.price is None or action.price_ticks_from_best is None:
                continue
            our_price = materialize_price_from_action(state, action)
            if our_price is None:
                continue
            if abs(our_price - oo.price) < state.venue.tick_size:
                return True
        return False

    def _would_exceed_leverage(
        self, state: MarketWorldState, action: FulfilmentAction, params: FulfilmentPolicyParams,
    ) -> bool:
        return state.account.total_notional / max(state.account.equity, 1e-12) > MAX_ACCOUNT_LEVERAGE

    def _would_exceed_symbol_notional(
        self, state: MarketWorldState, action: FulfilmentAction, params: FulfilmentPolicyParams,
    ) -> bool:
        if action.kind not in (ActionKind.PLACE, ActionKind.CANCEL_REPLACE, ActionKind.CROSS_SPREAD):
            return False
        price = materialize_price_from_action(state, action)
        if price is None:
            return False
        qty = action.qty_fraction * state.account.available_balance / max(price, 1e-12)
        order_notional = price * qty
        max_notional = state.account.equity * MAX_SYMBOL_NOTIONAL_FRACTION
        current_notional = 0.0
        for oo in state.open_orders:
            if oo.symbol == state.venue.symbol and oo.price is not None:
                current_notional += oo.price * oo.remaining_qty
        return (current_notional + order_notional) > max_notional

    def _post_only_would_cross(self, state: MarketWorldState, action: FulfilmentAction) -> bool:
        if not action.post_only:
            return False
        price = materialize_price_from_action(state, action)
        if price is None:
            return False
        if not state.book.bids or not state.book.asks:
            return False
        if action.side == Side.BUY and price >= state.book.best_ask:
            return True
        if action.side == Side.SELL and price <= state.book.best_bid:
            return True
        return False

    def _violates_venue_minima(self, state: MarketWorldState, action: FulfilmentAction) -> bool:
        if action.kind not in (ActionKind.PLACE, ActionKind.CANCEL_REPLACE):
            return False
        price = materialize_price_from_action(state, action)
        if price is None:
            return False
        if price <= 0:
            return True
        tick = state.venue.tick_size
        if tick > 0:
            remainder = price % tick
            if remainder > 1e-9 and tick - remainder > 1e-9:
                return True
        qty = action.qty_fraction * state.account.available_balance / max(price, 1e-12)
        lot = state.venue.lot_size
        if lot > 0 and qty > 0:
            rounded = round(qty / lot) * lot
            if rounded < state.venue.min_qty:
                return True
        notional = price * qty
        if notional < state.venue.min_notional:
            return True
        return False