/**
 * @copyright ngrx
 */
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { Observable } from 'rxjs/Observable';
import { Action, ActionReducer } from './index';
import { observeOn } from 'rxjs/operator/observeOn';
import { queue } from 'rxjs/scheduler/queue';
import { scan } from 'rxjs/operator/scan';

export class MiniState<T> extends BehaviorSubject<T> {
  constructor(_initialState: T, actionsDispatcher$: Observable<Action>, reducer: ActionReducer<T>) {
    super(_initialState);

    const actionInQueue$ = observeOn.call(actionsDispatcher$, queue);
    const state$ = scan.call(actionInQueue$, (state: T, action: Action) => {
      if (!action) {
        return state;
      }

      return reducer(state, action);
    }, _initialState);

    state$.subscribe((value: T) => this.next(value));
  }
}