import { createHash } from "node:crypto";

const WINDOW_MS = 60 * 1000;
const buckets = new Map();

function prune(now) {
  if (buckets.size < 2048) return;
  for (const [key, bucket] of buckets) {
    if (bucket.resetAt <= now) buckets.delete(key);
  }
}

export function rateLimitIdentity({ token = "", ipAddress = "" } = {}) {
  const normalizedToken = String(token || "").trim();
  if (normalizedToken) return `token:${createHash("sha256").update(normalizedToken).digest("hex")}`;
  return `ip:${String(ipAddress || "unknown").trim() || "unknown"}`;
}

export function consumeRateLimit({ key, limit, now = Date.now() } = {}) {
  const normalizedLimit = Math.max(0, Math.floor(Number(limit || 0)));
  if (!normalizedLimit) return null;
  const windowStart = Math.floor(now / WINDOW_MS) * WINDOW_MS;
  const bucketKey = `${String(key || "unknown")}:${windowStart}`;
  const resetAt = windowStart + WINDOW_MS;
  const current = buckets.get(bucketKey) || { count: 0, resetAt };
  current.count += 1;
  buckets.set(bucketKey, current);
  prune(now);
  return {
    allowed: current.count <= normalizedLimit,
    count: current.count,
    limit: normalizedLimit,
    remaining: Math.max(0, normalizedLimit - current.count),
    resetAt,
    retryAfter: Math.max(1, Math.ceil((resetAt - now) / 1000))
  };
}

export function rateLimitHeaders(result) {
  if (!result) return {};
  return {
    "x-ratelimit-limit": String(result.limit),
    "x-ratelimit-remaining": String(result.remaining),
    "x-ratelimit-reset": String(Math.ceil(result.resetAt / 1000)),
    ...(result.allowed ? {} : { "retry-after": String(result.retryAfter) })
  };
}