// backend/src/config/configuration.ts
export interface Config {
  port: number;
  database: {
    url: string;
  };
  jwt: {
    secret: string;
    expiresIn: string;
  };
  throttle: {
    ttl: number;
    limit: number;
  };
}

export default (): Config => {
  // Helper function to get required env var with type safety
  const getEnvVar = (key: string): string => {
    const value = process.env[key];
    if (!value) {
      throw new Error(`❌ Environment variable ${key} is required but not set`);
    }
    return value;
  };

  // Helper for optional env vars with defaults
  const getEnvVarWithDefault = (key: string, defaultValue: string): string => {
    return process.env[key] || defaultValue;
  };

  const getEnvVarAsNumber = (key: string, defaultValue: number): number => {
    const value = process.env[key];
    if (!value) return defaultValue;
    const parsed = parseInt(value, 10);
    return isNaN(parsed) ? defaultValue : parsed;
  };

  return {
    port: getEnvVarAsNumber('PORT', 3000),
    database: {
      url: getEnvVar('DATABASE_URL'),
    },
    jwt: {
      secret: getEnvVar('JWT_SECRET'),
      expiresIn: getEnvVarWithDefault('JWT_EXPIRES_IN', '7d'),
    },
    throttle: {
      ttl: getEnvVarAsNumber('THROTTLE_TTL', 60),
      limit: getEnvVarAsNumber('THROTTLE_LIMIT', 100),
    },
  };
};