"""Immutable, hash-chained audit trail. Every risk decision, mode change, order and kill-switch flip goes here."""

from __future__ import annotations

import hashlib
import json
from typing import Any

import asyncpg

from ktrade.logging import correlation_id


def _hash(prev: str | None, actor: str, action: str, entity: str | None, details: dict[str, Any]) -> str:
    payload = json.dumps({"p": prev, "a": actor, "x": action, "e": entity, "d": details}, sort_keys=True, default=str)
    return hashlib.sha256(payload.encode()).hexdigest()


async def audit(pool: asyncpg.Pool, actor: str, action: str, entity: str | None = None, details: dict[str, Any] | None = None) -> int:
    details = details or {}
    async with pool.acquire() as conn, conn.transaction():
        prev = await conn.fetchval("SELECT hash FROM audit_log ORDER BY id DESC LIMIT 1 FOR UPDATE")
        h = _hash(prev, actor, action, entity, details)
        return await conn.fetchval(
            "INSERT INTO audit_log (actor, action, entity, details, cid, prev_hash, hash) VALUES ($1,$2,$3,$4,$5,$6,$7) RETURNING id",
            actor, action, entity, json.loads(json.dumps(details, default=str)), correlation_id.get(), prev, h,
        )


async def verify_chain(pool: asyncpg.Pool, limit: int = 10000) -> tuple[bool, int]:
    rows = await pool.fetch("SELECT actor, action, entity, details, prev_hash, hash FROM audit_log ORDER BY id ASC LIMIT $1", limit)
    prev = None
    for i, r in enumerate(rows):
        if r["prev_hash"] != prev or _hash(prev, r["actor"], r["action"], r["entity"], r["details"]) != r["hash"]:
            return False, i
        prev = r["hash"]
    return True, len(rows)