from __future__ import annotations
from typing import Dict, Any, Optional
from .contract import SafetyContract


class ShadowPlanner:
    """Toy shadow planner for MVP: suggests a safer delta to the proposed plan.

    In a real system this would run a separate optimizer. Here we implement a simple heuristic:
    if the plan has a 'speed' parameter, cap it to a safe maximum; otherwise, return a reduced-cost plan.
    """

    SAFE_SPEED_MAX = 0.5

    def propose_safe(self, plan: Dict[str, Any], state: Dict[str, Any], contract: SafetyContract) -> Optional[Dict[str, Any]]:
        new_plan = plan.copy()
        costs = new_plan.get("costs", {})
        action = new_plan.get("action")
        # Simple heuristic: if speed present, cap it; otherwise, throttle time/cost if possible
        if "speed" in new_plan:
            if new_plan["speed"] > self.SAFE_SPEED_MAX:
                new_plan["speed"] = self.SAFE_SPEED_MAX
                new_plan["costs"] = {**costs, "time": max(costs.get("time", 0), 0.1)}
                return new_plan
        # If no speed but time can be reduced, reduce time fractionally
        if costs and costs.get("time", 0) > 0:
            new_plan_costs = dict(costs)
            new_plan_costs["time"] = max(costs["time"] * 0.8, 0.01)
            new_plan["costs"] = new_plan_costs
            return new_plan
        return None