State.ts

interface ATMState {
    name?: string;
    takeCash(cash: number): void;
  }
  
  class ATMHasCashState implements ATMState {
    private _machine: ATMMachine;
    name: string;
    constructor(machine: ATMMachine, name: string) {
      this.name = name;
      this._machine = machine;
    }
  
    takeCash(cash: number): void {
      if (this._machine.cash < cash) {
        this._machine.state = this._machine.noCashState();
        console.log('Not enough cash');
        return;
      } else if (this._machine.cash === cash) {
        this._machine.state = this._machine.noCashState();
        console.log('No cash after cash token');
      }
      console.log(`${this._machine.cash} - ${cash}`);
      this._machine.cash -= cash;
    }
  }
  
  class ATMNoCashState implements ATMState {
    private _machine: ATMMachine;
    name: string;
    constructor(machine: ATMMachine, name: string) {
      this.name = name;
      this._machine = machine;
    }
  
    takeCash(cash: number): void {
      throw new Error('ATMMachine has no cash');
    }
  }
  
  class ATMMachine implements ATMState {
  
    private _hasCashState: ATMHasCashState;
    private _noCashState: ATMNoCashState;
  
    private _currentState: ATMState;
    
    public cash: number;
    
    constructor(cash: number) {
      this.cash = cash;
  
      this._hasCashState = new ATMHasCashState(this, 'HasCash');
      this._noCashState = new ATMNoCashState(this, 'NoCash');
  
      this._currentState = this.cash ? this._hasCashState : this._noCashState;
    }
  
    public set state(value: ATMState) {
      console.log(`Current state is ${value.name}`);
      this._currentState = value;
    }
  
    public get state() {
      return this._currentState;
    }
  
    takeCash(cash: number): void {
      this._currentState.takeCash(cash);
    }
  
    // Get states
    public hasCashState() {
      return this._hasCashState;
    }
  
    public noCashState() {
      return this._noCashState;
    }
  }
  
// USAGE:
    const machine  = new ATMMachine(1000);
    machine.takeCash(200); // has cash
    machine.takeCash(1000); // not enough
// OUTPUT:
// "1000 - 200"
// "Current state is NoCash"
// "Not enough cash"