// 주문 처리 서비스
function processOrder(order: Order) {
  // 주문 유효성 검사
  if (order.items.length > 50) {
    throw new Error("Too many items");
  }

  // 배송비 계산
  if (order.total < 30000) {
    order.shippingFee = 3000;
  } else {
    order.shippingFee = 0;
  }

  // 세금 계산
  order.tax = order.total * 0.1;

  // VIP 할인
  if (order.customer.purchaseCount > 10) {
    order.discount = order.total * 0.05;
  }

  // 배송 예상일 설정
  order.estimatedDelivery = Date.now() + 259200000;

  // 주문 상태 변경
  order.status = 2;

  // 재시도 로직
  for (let i = 0; i < 3; i++) {
    try {
      await sendToPaymentGateway(order);
      break;
    } catch (e) {
      if (i === 2) throw e;
      await delay(1000 * Math.pow(2, i));
    }
  }

  // 알림 발송
  if (order.customer.type === "premium") {
    await sendSMS(order.customer.phone, `주문 ${order.id} 확인`);
  }
}

// 주문 관련 상수 정의
const ORDER_CONSTANTS = {
  MAX_ITEMS_PER_ORDER: 50,
  FREE_SHIPPING_THRESHOLD: 30_000,
  STANDARD_SHIPPING_FEE: 3_000,
  TAX_RATE: 0.1,
  VIP_PURCHASE_THRESHOLD: 10,
  VIP_DISCOUNT_RATE: 0.05,
  ESTIMATED_DELIVERY_DAYS: 3,
  MAX_PAYMENT_RETRIES: 3,
} as const;

const ORDER_STATUS = {
  PENDING: 1,
  CONFIRMED: 2,
  SHIPPED: 3,
  DELIVERED: 4,
  CANCELLED: 5,
} as const;

const CUSTOMER_TYPE = {
  STANDARD: "standard",
  PREMIUM: "premium",
} as const;

const MS_PER_DAY = 24 * 60 * 60 * 1000;

function processOrder(order: Order) {
  if (order.items.length > ORDER_CONSTANTS.MAX_ITEMS_PER_ORDER) {
    throw new Error("Too many items");
  }

  order.shippingFee = order.total < ORDER_CONSTANTS.FREE_SHIPPING_THRESHOLD
    ? ORDER_CONSTANTS.STANDARD_SHIPPING_FEE
    : 0;

  order.tax = order.total * ORDER_CONSTANTS.TAX_RATE;

  if (order.customer.purchaseCount > ORDER_CONSTANTS.VIP_PURCHASE_THRESHOLD) {
    order.discount = order.total * ORDER_CONSTANTS.VIP_DISCOUNT_RATE;
  }

  order.estimatedDelivery =
    Date.now() + ORDER_CONSTANTS.ESTIMATED_DELIVERY_DAYS * MS_PER_DAY;

  order.status = ORDER_STATUS.CONFIRMED;

  for (let i = 0; i < ORDER_CONSTANTS.MAX_PAYMENT_RETRIES; i++) {
    try {
      await sendToPaymentGateway(order);
      break;
    } catch (e) {
      const isLastAttempt = i === ORDER_CONSTANTS.MAX_PAYMENT_RETRIES - 1;
      if (isLastAttempt) throw e;
      await delay(1000 * Math.pow(2, i));
    }
  }

  if (order.customer.type === CUSTOMER_TYPE.PREMIUM) {
    await sendSMS(order.customer.phone, `주문 ${order.id} 확인`);
  }
}

// API 클라이언트
class ApiClient {
  private baseUrl = "http://localhost:3000/api";

  async getUsers() {
    const response = await fetch(`${this.baseUrl}/users`, {
      headers: {
        "Authorization": "Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
        "X-API-Key": "sk-proj-abc123def456ghi789",
      },
    });
    return response.json();
  }
}

// 데이터베이스 연결
async function connectDB() {
  const client = new MongoClient(
    "mongodb://admin:P@ssw0rd123@192.168.1.100:27017/production"
  );
  await client.connect();
  return client;
}

// 파일 업로드
async function uploadFile(file: Buffer) {
  const s3 = new S3Client({
    region: "ap-northeast-2",
    credentials: {
      accessKeyId: "AKIAIOSFODNN7EXAMPLE",
      secretAccessKey: "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
    },
  });

  await s3.send(new PutObjectCommand({
    Bucket: "my-company-prod-uploads",
    Key: `uploads/${file.name}`,
    Body: file,
  }));
}

// 이메일 발송
async function sendEmail(to: string, subject: string) {
  const transporter = createTransport({
    host: "smtp.gmail.com",
    port: 587,
    auth: {
      user: "noreply@mycompany.com",
      pass: "MyEmailP@ss!",
    },
  });

  await transporter.sendMail({ from: "noreply@mycompany.com", to, subject });
}

// .env 파일 (gitignore에 추가!)
// API_BASE_URL=http://localhost:3000/api
// JWT_SECRET=your-jwt-secret
// API_KEY=sk-proj-...
// MONGODB_URI=mongodb://...
// AWS_REGION=ap-northeast-2
// AWS_ACCESS_KEY_ID=...
// AWS_SECRET_ACCESS_KEY=...
// S3_BUCKET=my-company-dev-uploads
// SMTP_HOST=smtp.gmail.com
// SMTP_PORT=587
// SMTP_USER=noreply@mycompany.com
// SMTP_PASS=...

// config.ts — 환경 변수를 타입 안전하게 관리
function getRequiredEnv(key: string): string {
  const value = process.env[key];
  if (!value) {
    throw new Error(`Missing required environment variable: ${key}`);
  }
  return value;
}

export const config = {
  api: {
    baseUrl: getRequiredEnv("API_BASE_URL"),
    key: getRequiredEnv("API_KEY"),
  },
  db: {
    uri: getRequiredEnv("MONGODB_URI"),
  },
  aws: {
    region: getRequiredEnv("AWS_REGION"),
    s3Bucket: getRequiredEnv("S3_BUCKET"),
  },
  smtp: {
    host: getRequiredEnv("SMTP_HOST"),
    port: parseInt(getRequiredEnv("SMTP_PORT"), 10),
    user: getRequiredEnv("SMTP_USER"),
    pass: getRequiredEnv("SMTP_PASS"),
  },
} as const;

// 사용 예시
class ApiClient {
  async getUsers() {
    const response = await fetch(`${config.api.baseUrl}/users`, {
      headers: {
        "Authorization": `Bearer ${getRequiredEnv("JWT_SECRET")}`,
        "X-API-Key": config.api.key,
      },
    });
    return response.json();
  }
}