<?php

namespace App\Middleware;

use App\Core\Request;
use App\Core\Response;
use Predis\Client as RedisClient;
use Exception;
use Throwable;

class RateLimit implements MiddlewareInterface
{
    private ?RedisClient $redis = null;
    private int $limit = 100; // Allow 100 requests
    private int $window = 60; // Per 60 seconds

    public function __construct()
    {
        $config = require __DIR__ . '/../../config/redis.php';
        if (!empty($config['host'])) {
            try {
                $this->redis = new RedisClient([
                    'scheme' => 'tcp',
                    'host'   => $config['host'],
                    'port'   => $config['port'],
                    'password' => $config['password'],
                    'timeout' => 0.5, // 500ms connection timeout to fail fast
                ]);
                $this->redis->connect();
            } catch (Throwable $e) {
                // Degrade gracefully if Redis server is down
                $this->redis = null;
            }
        }
    }

    /**
     * Handle rate limiting logic.
     */
    public function handle(Request $request, Response $response, callable $next): void
    {
        if ($this->redis === null) {
            // Redis unavailable, skip throttle check to avoid service outage
            $next();
            return;
        }

        $ip = $request->getIp();
        $path = $request->getPath();
        $key = "rate_limit:" . md5($ip . ":" . $path);

        try {
            $current = $this->redis->get($key);

            if ($current !== null && (int)$current >= $this->limit) {
                $ttl = $this->redis->ttl($key);
                $response->header('Retry-After', (string)max(1, $ttl));
                throw new Exception("Too Many Requests. Rate limit exceeded.", 429);
            }

            if ($current === null) {
                // First request in the time frame window
                $this->redis->setex($key, $this->window, 1);
                $current = 0;
            } else {
                $this->redis->incr($key);
            }

            // Set rate limit headers
            $remaining = $this->limit - ((int)$current + 1);
            $response->header('X-RateLimit-Limit', (string)$this->limit);
            $response->header('X-RateLimit-Remaining', (string)max(0, $remaining));

        } catch (Throwable $e) {
            if ($e->getCode() === 429) {
                throw $e;
            }
            // Logging or catching connection dropping mid-request
        }

        $next();
    }
}