export class StateMachine {
  private _states: Map<string, State> = new Map();
  private currentState: State;

  constructor(states: State[]) {
    this.currentState = states[0];
  }

  update(dt: number) {
    this.currentState.update(dt);
  }

  get current() {
    return this.currentState;
  }

  get states() {
    return this._states;
  }

  addState(state: State) {
    this.states.set(state.name, state);
  }

  transitionTo(state: State) {
    if (this.current.canTransitionTo(state)) {
      this.current.stop();
      this.currentState = state;
      this.current.start();
    }
  }
}

export abstract class State<T> {
  private stateMachine: StateMachine;
  protected abstract validTransitions: Set<T>;

  abstract readonly name: T;

  constructor(
    stateMachine: StateMachine,
  ) {
    this.stateMachine = stateMachine;
  }

  abstract update(dt: number): void;
  abstract start(): void;
  abstract stop(): void;

  canTransitionTo(state: T) {
    return this.validTransitions.has(state);
  }
}