import { Request, Response, NextFunction } from "express";

interface ThrottleConfig {
  windowMs: number;
  maxRequests: number;
}

const throttleConfigs: Map<string, ThrottleConfig> = new Map();
const requestCounts: Map<string, { count: number; resetAt: number }> = new Map();

/**
 * API throttling middleware
 */
export function apiThrottle(config: ThrottleConfig) {
  return (req: Request, res: Response, next: NextFunction) => {
    const key = req.headers["x-api-key"] as string || req.ip || "unknown";
    const now = Date.now();

    let record = requestCounts.get(key);
    if (!record || now > record.resetAt) {
      record = {
        count: 0,
        resetAt: now + config.windowMs,
      };
      requestCounts.set(key, record);
    }

    record.count++;

    // Set rate limit headers
    res.setHeader("X-RateLimit-Limit", config.maxRequests.toString());
    res.setHeader("X-RateLimit-Remaining", Math.max(0, config.maxRequests - record.count).toString());
    res.setHeader("X-RateLimit-Reset", new Date(record.resetAt).toISOString());

    if (record.count > config.maxRequests) {
      return res.status(429).json({
        error: "Rate limit exceeded",
        message: `Maximum ${config.maxRequests} requests per ${config.windowMs}ms`,
        retryAfter: Math.ceil((record.resetAt - now) / 1000),
      });
    }

    next();
  };
}

/**
 * Set throttle configuration for a route
 */
export function setThrottleConfig(path: string, config: ThrottleConfig) {
  throttleConfigs.set(path, config);
}