import * as I from 'immutable';

export class StateSynchronizer {

  constructor(statefuls) {
    this._state = I.Map();
    this._statefuls = statefuls;
    this.tick();
  }

  static nextStep(step) {
    const {path, op, value} = step;
    const parts = path.split('/');
    const [key] = parts.splice(1, 1);
    const subpath = parts.join('/');
    return [key, {
      op,
      path: subpath ? subpath : '/',
      value,
    }];
  }

  patchState(patch) {
    const stepMap = {};
    for (const {op, path, value} of patch) {
      const parts = path.split('/');
      const [key] = parts.splice(1, 1);
      if (!stepMap[key]) {
        stepMap[key] = [];
      }
      const subpath = parts.join('/');
      stepMap[key].push({
        op,
        path: subpath ? subpath : '/',
        value,
      });
    }
    for (const key in stepMap) {
      const stateful = this._statefuls[key];
      if (!stateful) {
        continue;
      }
      stateful.patchState(stepMap[key]);
    }
  }

  get state() {
    return this._state;
  }

  tick() {
    for (const key in this._statefuls) {
      const stateful = this._statefuls[key];
      this._state = this._state.set(key, stateful.state);
    }
  }

}