StateTransition.js

import { action, observable } from 'mobx';

export function withStateTransition(target) {
  return class StateTransitionInjector extends target {
    @observable state = 'idle';

    @action
    setState(state) {
      this.state = state;
    }
  };
}

export function stateTransition(startState, endState) {
  return function(target, name, descriptor) {
    const original = descriptor.value;

    descriptor.value = async function(...args) {
      this.setState(startState);
      try {
        await original.apply(this, args);
        this.setState(endState);
      } catch (e) {
        this.setState('error');
        throw e;
      }
    };

    return descriptor;
  };
}

@withStateTransition
export class StateTransition {}