<?php

namespace App\Core;

/**
 * Core Redis Client for managing connections.
 * Handles Sessions, Rate Limiting, OTP, and Caching.
 */
class RedisClient
{
    private static ?\Redis $instance = null;

    /**
     * Get the singleton Redis connection instance
     */
    public static function getInstance(): \Redis
    {
        if (self::$instance === null) {
            $host     = getenv('REDIS_HOST');
            $port     = getenv('REDIS_PORT');
            $password = getenv('REDIS_PASSWORD');

            $missing = [];
            if ($host === false || $host === '') $missing[] = 'REDIS_HOST';
            if ($port === false || $port === '') $missing[] = 'REDIS_PORT';

            if (!empty($missing)) {
                throw new \RuntimeException("Redis Configuration Error: Missing environment variable(s): " . implode(', ', $missing));
            }

            try {
                $redis = new \Redis();
                
                // Connect with a 2.5 second timeout
                if (!$redis->connect($host, (int)$port, 2.5)) {
                    throw new \RuntimeException("Could not connect to Redis server at {$host}:{$port}");
                }

                // Authenticate ONLY if a non-empty password is provided in environment
                if (!empty($password)) {
                    try {
                        if (!$redis->auth($password)) {
                            throw new \RuntimeException("Redis authentication failed with provided REDIS_PASSWORD.");
                        }
                    } catch (\RedisException $authEx) {
                        // If server does not have a password configured, catch and report clearly
                        if (str_contains($authEx->getMessage(), 'no password is set') || str_contains($authEx->getMessage(), 'without any password')) {
                            error_log("⚠️ [Redis Notice] REDIS_PASSWORD was provided in .env, but Redis server on {$host}:{$port} is configured without password.");
                        } else {
                            throw $authEx;
                        }
                    }
                }

                // Set prefix for Saqel to avoid collisions
                $redis->setOption(\Redis::OPT_PREFIX, 'saqel:');

                self::$instance = $redis;
            } catch (\Exception $e) {
                error_log("Redis Connection Error: " . $e->getMessage());
                throw new \RuntimeException("Redis connection failed ({$host}:{$port}): " . $e->getMessage());
            }
        }

        return self::$instance;
    }
    
    /**
     * Helper to close the connection explicitly
     */
    public static function close(): void
    {
        if (self::$instance !== null) {
            self::$instance->close();
            self::$instance = null;
        }
    }
}