class EnvironmentValidator {
    static validateEnvironment() {
        const requiredEnvVars = [
            'TELEGRAM_BOT_TOKEN',
            'API_BASE_URL'
        ];

        const missingVars = [];
        const invalidVars = [];

        for (const envVar of requiredEnvVars) {
            const value = process.env[envVar];
            
            if (!value) {
                missingVars.push(envVar);
                continue;
            }

            // Validate specific environment variables
            switch (envVar) {
                case 'TELEGRAM_BOT_TOKEN':
                    if (!this.validateTelegramToken(value)) {
                        invalidVars.push(`${envVar}: Invalid token format`);
                    }
                    break;
                    
                case 'API_BASE_URL':
                    if (!this.validateApiUrl(value)) {
                        invalidVars.push(`${envVar}: Invalid URL format`);
                    }
                    break;
            }
        }

        if (missingVars.length > 0) {
            console.error('❌ Missing required environment variables:');
            missingVars.forEach(varName => {
                console.error(`   - ${varName}`);
            });
            console.error('\nPlease check your .env file and ensure all required variables are set.');
            return false;
        }

        if (invalidVars.length > 0) {
            console.error('❌ Invalid environment variables:');
            invalidVars.forEach(error => {
                console.error(`   - ${error}`);
            });
            return false;
        }

        console.log('✅ Environment validation passed');
        return true;
    }

    static validateTelegramToken(token) {
        // Telegram bot tokens have a specific format: number:string
        const tokenRegex = /^\d+:[A-Za-z0-9_-]{35}$/;
        return tokenRegex.test(token);
    }

    static validateApiUrl(url) {
        try {
            const parsedUrl = new URL(url);
            
            // Ensure HTTPS in production (allow HTTP for development)
            if (process.env.NODE_ENV === 'production' && parsedUrl.protocol !== 'https:') {
                console.warn('⚠️  WARNING: Using HTTP in production is not secure');
                return false;
            }
            
            return ['http:', 'https:'].includes(parsedUrl.protocol);
        } catch (error) {
            return false;
        }
    }

    static getSecureConfig() {
        return {
            telegramBotToken: process.env.TELEGRAM_BOT_TOKEN,
            apiBaseUrl: process.env.API_BASE_URL,
            websiteUrl: process.env.WEBSITE_URL || 'https://yaltipia.com/listings',
            nodeEnv: process.env.NODE_ENV || 'development',
            isProduction: process.env.NODE_ENV === 'production'
        };
    }
}

module.exports = EnvironmentValidator;