import {Inject} from '@angular/core';
import {RecordCollection} from './record-collection';
import {
  Observable,
  Subject
} from 'rxjs/Rx';
import _ from 'lodash';
import {RecordStoreService} from '../records/record-store.service';

export class RecordsProvider {
  sources: Observable<RecordCollection>[] = [];
  sourceAdded: Subject<Observable<RecordCollection>>;
  sourceRemoved: Subject<Observable<RecordCollection>>;

  constructor(
    @Inject(RecordStoreService) private recordStore: RecordStoreService) {
    this.sourceAdded =
      new Subject<Observable<RecordCollection>>();
    this.sourceRemoved =
      new Subject<Observable<RecordCollection>>();

    this._populateFromStore(recordStore);
  }

  add(collection: RecordCollection)
  : Observable<RecordCollection> {
    const obs = Observable.of(collection);

    this.sources.push(obs);
    this.sourceAdded.next(obs);
    this.recordStore.put(collection);

    return obs;
  }

  addSource(source: Observable<RecordCollection>)
  : Observable<RecordCollection> {
    const observable = Observable.create(obs => {
      source.subscribe({
        next: rc => obs.next(rc),
        error: err => obs.error(err)
      });
    });

    this.sources.push(observable);
    this.sourceAdded.next(observable);

    source.subscribe(rc => this.recordStore.put(rc));

    return observable;
  }

  removeSource(source: Observable<RecordCollection>)
  : Observable<RecordCollection> {
    const removedSource = _(this.sources)
      .remove(src => src === source)
      .head();

    this.sourceRemoved.next(removedSource);

    removedSource.subscribe(col => {
      this.recordStore.remove(col);
    });

    return removedSource;
  }

  private _populateFromStore(recordStore: RecordStoreService): void {
    recordStore.allDocs().subscribe(docs => {
      _.forEach(docs, rc => {
        const obs = Observable.of(rc);
        this.sources.push(obs);
        this.sourceAdded.next(obs);
      });
    });
  }
}