/**
 * @fileoverview Simple in-memory per-tenant rate limiter.
 * @module middleware/rateLimit
 */

import { AppError, asyncHandler } from '../errors.js';
import { getTenant, resolveLimits } from '../store/tenants.js';
import { createDebugger } from '../debug/logger.js';

const log = createDebugger('billing');

/** @type {Map<string, { windowStart: number, count: number }>} */
const windows = new Map();

/**
 * Reset rate limit windows (tests).
 * @returns {void}
 */
export function resetRateLimitWindows() {
  windows.clear();
}

/**
 * Enforce plan requestsPerMinute using a 60s sliding fixed window.
 */
export const rateLimit = asyncHandler(async (req, res, next) => {
  const tenantId = req.auth?.tenantId;
  if (!tenantId) return next();

  const tenant = getTenant(tenantId);
  const limits = tenant
    ? resolveLimits(tenant)
    : { requestsPerMinute: 30 };

  const rpm = limits.requestsPerMinute ?? 30;
  const now = Date.now();
  const windowMs = 60_000;

  let entry = windows.get(tenantId);
  if (!entry || now - entry.windowStart >= windowMs) {
    entry = { windowStart: now, count: 0 };
    windows.set(tenantId, entry);
  }

  entry.count += 1;
  if (entry.count > rpm) {
    log.debug('rate limited', { tenantId, count: entry.count, rpm });
    throw new AppError('Rate limit exceeded', {
      status: 429,
      code: 'RATE_LIMITED',
      details: { requestsPerMinute: rpm },
    });
  }

  next();
});