from __future__ import annotations

from dataclasses import dataclass, asdict
from typing import List, Dict, Any


@dataclass(frozen=True)
class CanonicalPlan:
    projection: List[str]
    predicates: List[str]
    estimated_cost: float

    def to_dict(self) -> Dict[str, Any]:
        return asdict(self)

    @staticmethod
    def from_dict(d: Dict[str, Any]) -> "CanonicalPlan":
        return CanonicalPlan(
            projection=list(d.get("projection", [])),
            predicates=list(d.get("predicates", [])),
            estimated_cost=float(d.get("estimated_cost", 0.0)),
        )