Order state

interface OrderState {
  cancel(order: Order): void;
  name(): string;
}

class Order {
  constructor(private state: OrderState) {}

  setState(state: OrderState) {
    this.state = state;
  }

  cancel() {
    this.state.cancel(this);
  }

  printStatus() {
    console.log(`Order is ${this.state.name()}`);
  }
}

class PendingState implements OrderState {
  cancel(order: Order) {
    console.log("Cancelling pending order.");
    order.setState(new CancelledState());
  }

  name() {
    return "pending";
  }
}

class ShippedState implements OrderState {
  cancel() {
    console.log("Shipped orders cannot be cancelled.");
  }

  name() {
    return "shipped";
  }
}

class CancelledState implements OrderState {
  cancel() {
    console.log("Order is already cancelled.");
  }

  name() {
    return "cancelled";
  }
}

const order = new Order(new PendingState());

order.printStatus();
order.cancel();
order.printStatus();

order.setState(new ShippedState());
order.cancel();