/**
 * Rate Limiting Middleware
 * 
 * Simple in-memory rate limiter.
 * For production, consider using Redis-backed solution.
 */

import { config } from '../config.js';

// In-memory store for request counts
const requestCounts = new Map();

// Cleanup old entries periodically
setInterval(() => {
    const now = Date.now();
    for (const [key, data] of requestCounts) {
        if (now - data.windowStart > config.rateLimitWindowMs * 2) {
            requestCounts.delete(key);
        }
    }
}, 60000); // Every minute

/**
 * Get client identifier from request
 */
function getClientId(req) {
    // Use X-Forwarded-For header if behind proxy
    const forwarded = req.headers['x-forwarded-for'];
    if (forwarded) {
        return forwarded.split(',')[0].trim();
    }
    return req.ip || (req.connection ? req.connection.remoteAddress : null) || 'unknown';
}

/**
 * Rate limiting middleware
 */
export function rateLimit(req, res, next) {
    const clientId = getClientId(req);
    const now = Date.now();

    let data = requestCounts.get(clientId);

    if (!data || now - data.windowStart > config.rateLimitWindowMs) {
        // New window
        data = {
            windowStart: now,
            count: 1
        };
        requestCounts.set(clientId, data);
        next();
        return;
    }

    data.count++;

    if (data.count > config.rateLimitMaxRequests) {
        const retryAfter = Math.ceil((data.windowStart + config.rateLimitWindowMs - now) / 1000);

        res.set('Retry-After', retryAfter.toString());
        res.set('X-RateLimit-Limit', config.rateLimitMaxRequests.toString());
        res.set('X-RateLimit-Remaining', '0');
        res.set('X-RateLimit-Reset', new Date(data.windowStart + config.rateLimitWindowMs).toISOString());

        return res.status(429).json({
            error: 'Too many requests',
            retry_after: retryAfter
        });
    }

    // Add rate limit headers
    res.set('X-RateLimit-Limit', config.rateLimitMaxRequests.toString());
    res.set('X-RateLimit-Remaining', (config.rateLimitMaxRequests - data.count).toString());
    res.set('X-RateLimit-Reset', new Date(data.windowStart + config.rateLimitWindowMs).toISOString());

    next();
}