feat: implement phase1 state machine, composite exits, and kill-switch orchestration (#275)

src/strategy/exit_rules.py

@@ -0,0 +1,104 @@
+"""Composite exit rules: hard stop, break-even lock, ATR trailing, model assist."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from src.strategy.position_state_machine import PositionState, StateTransitionInput, promote_state
+
+
+@dataclass(frozen=True)
+class ExitRuleConfig:
+    hard_stop_pct: float = -2.0
+    be_arm_pct: float = 1.2
+    arm_pct: float = 3.0
+    atr_multiplier_k: float = 2.2
+    model_prob_threshold: float = 0.62
+
+
+@dataclass(frozen=True)
+class ExitRuleInput:
+    current_price: float
+    entry_price: float
+    peak_price: float
+    atr_value: float = 0.0
+    pred_down_prob: float = 0.0
+    liquidity_weak: bool = False
+
+
+@dataclass(frozen=True)
+class ExitEvaluation:
+    state: PositionState
+    should_exit: bool
+    reason: str
+    unrealized_pnl_pct: float
+    trailing_stop_price: float | None
+
+
+def evaluate_exit(
+    *,
+    current_state: PositionState,
+    config: ExitRuleConfig,
+    inp: ExitRuleInput,
+) -> ExitEvaluation:
+    """Evaluate composite exit logic and return updated state."""
+    if inp.entry_price <= 0 or inp.current_price <= 0:
+        return ExitEvaluation(
+            state=current_state,
+            should_exit=False,
+            reason="invalid_price",
+            unrealized_pnl_pct=0.0,
+            trailing_stop_price=None,
+        )
+
+    unrealized = (inp.current_price - inp.entry_price) / inp.entry_price * 100.0
+    hard_stop_hit = unrealized <= config.hard_stop_pct
+    take_profit_hit = unrealized >= config.arm_pct
+
+    trailing_stop_price: float | None = None
+    trailing_stop_hit = False
+    if inp.atr_value > 0 and inp.peak_price > 0:
+        trailing_stop_price = inp.peak_price - (config.atr_multiplier_k * inp.atr_value)
+        trailing_stop_hit = inp.current_price <= trailing_stop_price
+
+    be_lock_threat = current_state in (PositionState.BE_LOCK, PositionState.ARMED) and (
+        inp.current_price <= inp.entry_price
+    )
+    model_exit_signal = inp.pred_down_prob >= config.model_prob_threshold and inp.liquidity_weak
+
+    next_state = promote_state(
+        current=current_state,
+        inp=StateTransitionInput(
+            unrealized_pnl_pct=unrealized,
+            be_arm_pct=config.be_arm_pct,
+            arm_pct=config.arm_pct,
+            hard_stop_hit=hard_stop_hit,
+            trailing_stop_hit=trailing_stop_hit,
+            model_exit_signal=model_exit_signal,
+            be_lock_threat=be_lock_threat,
+        ),
+    )
+
+    if hard_stop_hit:
+        reason = "hard_stop"
+    elif trailing_stop_hit:
+        reason = "atr_trailing_stop"
+    elif be_lock_threat:
+        reason = "be_lock_threat"
+    elif model_exit_signal:
+        reason = "model_liquidity_exit"
+    elif take_profit_hit:
+        # Backward-compatible immediate profit-taking path.
+        reason = "arm_take_profit"
+    else:
+        reason = "hold"
+
+    should_exit = next_state == PositionState.EXITED or take_profit_hit
+
+    return ExitEvaluation(
+        state=next_state,
+        should_exit=should_exit,
+        reason=reason,
+        unrealized_pnl_pct=unrealized,
+        trailing_stop_price=trailing_stop_price,
+    )