from __future__ import annotations

import hashlib
import json
from dataclasses import dataclass
from datetime import datetime
from typing import List


@dataclass
class GovernanceEntry:
    contract_id: str
    action: str
    signer: str
    timestamp: str
    version: int
    payload_hash: str | None = None


class GovernanceLedger:
    def __init__(self) -> None:
        self._entries: List[GovernanceEntry] = []
        self._last_hash: str | None = None

    def _hash_entry(self, entry: GovernanceEntry) -> str:
        data = {
            "contract_id": entry.contract_id,
            "action": entry.action,
            "signer": entry.signer,
            "timestamp": entry.timestamp,
            "version": entry.version,
            "payload_hash": entry.payload_hash,
            "prev_hash": self._last_hash,
        }
        return hashlib.sha256(json.dumps(data, sort_keys=True).encode("utf-8")).hexdigest()

    def append(self, contract_id: str, action: str, signer: str, version: int, payload_hash: str | None = None) -> GovernanceEntry:
        entry = GovernanceEntry(
            contract_id=contract_id,
            action=action,
            signer=signer,
            timestamp=datetime.utcnow().isoformat() + "Z",
            version=version,
            payload_hash=payload_hash,
        )
        self._entries.append(entry)
        self._last_hash = self._hash_entry(entry)
        return entry

    def entries(self) -> List[GovernanceEntry]:
        return list(self._entries)

    def latest_hash(self) -> str | None:
        return self._last_hash


__all__ = ["GovernanceLedger", "GovernanceEntry"]