"""Governance ledger for MarketMesh (tamper-evident audit logs).

This is a lightweight, in-memory audit log with a simple hash-chain to
provide tamper-evident properties for reproducibility and compliance.
"""
from __future__ import annotations

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


def _hash_chain(prev_hash: str, payload: Dict[str, Any]) -> str:
    data = (prev_hash or "") + str(payload)
    return hashlib.sha256(data.encode("utf-8")).hexdigest()


@dataclass
class AuditLogEntry:
    index: int
    timestamp: float
    contract_id: str
    action: str
    details: Dict[str, Any]
    previous_hash: str
    hash: str

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


class GovernanceLedger:
    """In-memory tamper-evident governance log."""

    def __init__(self) -> None:
        self._entries: List[AuditLogEntry] = []
        self._last_hash: str = ""

    def log(self, contract_id: str, action: str, details: Dict[str, Any] | None = None) -> AuditLogEntry:
        details = details or {}
        entry_index = len(self._entries) + 1
        payload = {
            "contract_id": contract_id,
            "action": action,
            "details": details,
        }
        entry_hash = _hash_chain(self._last_hash, payload)
        entry = AuditLogEntry(
            index=entry_index,
            timestamp=time(),
            contract_id=contract_id,
            action=action,
            details=details,
            previous_hash=self._last_hash,
            hash=entry_hash,
        )
        self._entries.append(entry)
        self._last_hash = entry_hash
        return entry

    def get_logs(self) -> List[AuditLogEntry]:
        return list(self._entries)