设计就是把事物拆分。。。用一种之后可以拼接在一起的方法。。。把事物拆分成可以组合在一起的事物就是设计 -- Rich Hickey《设计、重组和性能》

Clean Architecture

src/
|_domain/
  |_user.ts
  |_product.ts
  |_order.ts
  |_cart.ts
|_application/
  |_addToCart.ts
  |_authenticate.ts
  |_orderProducts.ts
  |_ports.ts
|_services/
  |_authAdapter.ts
  |_notificationAdapter.ts
  |_paymentAdapter.ts
  |_storageAdapter.ts
  |_api.ts
  |_store.tsx
|_lib/
|_ui/

• product
• user
• order
• shopping cart

// domain/user.ts

export type UserName = string;
export type User = {
  id: UniqueId;
  name: UserName;
  email: Email;
  preferences: Ingredient[];
  allergies: Ingredient[];
};

// domain/product.ts

export type ProductTitle = string;
export type Product = {
  id: UniqueId;
  title: ProductTitle;
  price: PriceCents;
  toppings: Ingredient[];
};

// domain/cart.ts

import { Product } from "./product";

export type Cart = {
  products: Product[];
};

// domain/order.ts

export type OrderStatus = "new" | "delivery" | "completed";

export type Order = {
  user: UniqueId;
  cart: Cart;
  created: DateTimeString;
  status: OrderStatus;
  total: PriceCents;
};

// domain/user.ts

export function hasAllergy(user: User, ingredient: Ingredient): boolean {
  return user.allergies.includes(ingredient);
}

export function hasPreference(user: User, ingredient: Ingredient): boolean {
  return user.preferences.includes(ingredient);
}

// domain/cart.ts

export function addProduct(cart: Cart, product: Product): Cart {
  return { ...cart, products: [...cart.products, product] };
}

export function contains(cart: Cart, product: Product): boolean {
  return cart.products.some(({ id }) => id === product.id);
}

// domain/product.ts

export function totalPrice(products: Product[]): PriceCents {
  return products.reduce((total, { price }) => total + price, 0);
}

// domain/order.ts

export function createOrder(user: User, cart: Cart): Order {
  return {
    user: user.id,
    cart,
    created: new Date().toISOString(),
    status: "new",
    total: totalPrice(products),
  };
}

// shared-kernel.d.ts

type Email = string;
type UniqueId = string;
type DateTimeString = string;
type PriceCents = number;

type OrderProducts = (user: User, cart: Cart) => Promise<void>;

// application/ports.ts

export interface PaymentService {
  tryPay(amount: PriceCents): Promise<boolean>;
}

// application/ports.ts

export interface NotificationService {
  notify(message: string): void;
}

// application/ports.ts

export interface OrdersStorageService {
  orders: Order[];
  updateOrders(orders: Order[]): void;
}

// application/orderProducts.ts

const payment: PaymentService = {};
const notifier: NotificationService = {};
const orderStorage: OrdersStorageService = {};

// application/orderProducts.ts
//...

async function orderProducts(user: User, cart: Cart) {
  const order = createOrder(user, cart);
}

// application/orderProducts.ts
//...

async function orderProducts(user: User, cart: Cart) {
  const order = createOrder(user, cart);

  // Try to pay for the order;
  // Notify the user if something is wrong:
  const paid = await payment.tryPay(order.total);
  if (!paid) return notifier.notify("Oops! 🤷");

  // Save the result and clear the cart:
  const { orders } = orderStorage;
  orderStorage.updateOrders([...orders, order]);
  cartStorage.emptyCart();
}

// ui/components/Buy.tsx

export function Buy() {
  // Get access to the use case in the component:
  const { orderProducts } = useOrderProducts();

  async function handleSubmit(e: React.FormEvent) {
    setLoading(true);
    e.preventDefault();

    // Call the use case function:
    await orderProducts(user!, cart);
    setLoading(false);
  }

  return (
    <section>
      <h2>Checkout</h2>
      <form onSubmit={handleSubmit}>{/* ... */}</form>
    </section>
  );
}

// application/orderProducts.ts

export function useOrderProducts() {
  const notifier = useNotifier();
  const payment = usePayment();
  const orderStorage = useOrdersStorage();

  async function orderProducts(user: User, cookies: Cookie[]) {
    // …
  }

  return { orderProducts };
}

// services/paymentAdapter.ts

import { fakeApi } from "./api";
import { PaymentService } from "../application/ports";

export function usePayment(): PaymentService {
  return {
    tryPay(amount: PriceCents) {
      return fakeApi(true);
    },
  };
}

// services/api.ts

export function fakeApi<TResponse>(response: TResponse): Promise<TResponse> {
  return new Promise((res) => setTimeout(() => res(response), 450));
}

// services/notificationAdapter.ts

import { NotificationService } from "../application/ports";

export function useNotifier(): NotificationService {
  return {
    notify: (message: string) => window.alert(message),
  };
}

// store.tsx

const StoreContext = React.createContext<any>({});
export const useStore = () => useContext(StoreContext);

export const Provider: React.FC = ({ children }) => {
  // ...Other entities...
  const [orders, setOrders] = useState([]);

  const value = {
    // ...
    orders,
    updateOrders: setOrders,
  };

  return (
    <StoreContext.Provider value={value}>{children}</StoreContext.Provider>
  );
};

// services/storageAdapter.ts

export function useOrdersStorage(): OrdersStorageService {
  return useStore();
}

// shared-kernel.d.ts

type PriceCents = number;

type Currency = "RUB" | "USD" | "EUR" | "SEK";
type AmountCents = number;

type Price = {
  value: AmountCents;
  currency: Currency;
};

import { Product, totalPrice } from "./product";

export function createOrder(user: User, cart: Cart): Order {
  return {
    user: user.id,
    cart,
    created: new Date().toISOString(),
    status: "new",
    total: totalPrice(products),
  };
}

import { Product, totalPrice } from "./product";

export function createOrder(user: User, cart: Cart): Order {
  return {
    user: user.id,
    cart,

    // Вот эта строка:
    created: new Date().toISOString(),

    status: "new",
    total: totalPrice(products),
  };
}

// lib/datetime.ts

export function currentDatetime(): DateTimeString {
  return new Date().toISOString();
}

// domain/order.ts

import { currentDatetime } from "../lib/datetime";
import { Product, totalPrice } from "./product";

export function createOrder(user: User, cart: Cart): Order {
  return {
    user: user.id,
    cart,
    created: currentDatetime(),
    status: "new",
    total: totalPrice(products),
  };
}

// domain/order.ts

export function createOrder(
  user: User,
  cart: Cart,
  created: DateTimeString
): Order {
  return {
    user: user.id,
    products,
    created,
    status: "new",
    total: totalPrice(products),
  };
}

function someUserCase() {
  // Use the `dateTimeSource` adapter,
  // to get the current date in the desired format:
  const createdOn = dateTimeSource.currentDatetime();

  // Pass already created date to the domain function:
  createOrder(user, cart, createdOn);
}

export type Cart = {
  products: Product[];
};

export type Order = {
  user: UniqueId;
  cart: Cart;
  created: DateTimeString;
  status: OrderStatus;
  total: PriceCents;
};

type ProductList = Product[];

type Cart = {
  products: ProductList;
};

type Order = {
  user: UniqueId;
  products: ProductList;
  created: DateTimeString;
  status: OrderStatus;
  total: PriceCents;
};

// application/orderProducts.ts

export function useOrderProducts() {
  const notifier = useNotifier();
  const payment = usePayment();
  const orderStorage = useOrdersStorage();
  const cartStorage = useCartStorage();

  async function orderProducts(user: User, cart: Cart) {
    const order = createOrder(user, cart);

    const paid = await payment.tryPay(order.total);
    if (!paid) return notifier.notify("Oops! 🤷");

    const { orders } = orderStorage;
    orderStorage.updateOrders([...orders, order]);
    cartStorage.emptyCart();
  }

  return { orderProducts };
}

type Dependencies = {
  notifier?: NotificationService;
  payment?: PaymentService;
  orderStorage?: OrderStorageService;
};

async function orderProducts(
  user: User,
  cart: Cart,
  dependencies: Dependencies = defaultDependencies
) {
  const { notifier, payment, orderStorage } = dependencies;

  // ...
}

function useOrderProducts() {
  const notifier = useNotifier();
  const payment = usePayment();
  const orderStorage = useOrdersStorage();

  return (user: User, cart: Cart) =>
    orderProducts(user, cart, {
      notifier,
      payment,
      orderStorage,
    });
}

export function useOrderProducts() {
  // Here we use hooks to get the instances of each service,
  // which will be used inside the orderProducts use case:
  const notifier = useNotifier();
  const payment = usePayment();
  const orderStorage = useOrdersStorage();
  const cartStorage = useCartStorage();

  async function orderProducts(user: User, cart: Cart) {
    // ...Inside the use case we use those services.
  }

  return { orderProducts };
}