"""Governance primitives for BeXProof policy changes."""
from __future__ import annotations
from typing import Dict, Set


class Governance:
    def __init__(self, signers: Set[str] = None, required: int = 2):
        self.signers = set(signers or {"alice", "bob", "carol"})
        self.required = max(1, min(len(self.signers), required))
        self.proposals: Dict[str, Dict] = {}
        self.approvals: Dict[str, Set[str]] = {}

    def propose(self, policy_id: str, policy_text: str) -> None:
        self.proposals[policy_id] = {"policy": policy_text, "approved": False}
        self.approvals[policy_id] = set()

    def approve(self, policy_id: str, signer: str) -> bool:
        if signer not in self.signers:
            return False
        if policy_id not in self.proposals:
            return False
        self.approvals[policy_id].add(signer)
        if len(self.approvals[policy_id]) >= self.required:
            self.proposals[policy_id]["approved"] = True
        return True

    def is_approved(self, policy_id: str) -> bool:
        return bool(self.proposals.get(policy_id, {}).get("approved", False))