patch-db/client/lib/patch-db.ts

import { EMPTY, merge, Observable, ReplaySubject, Subject } from 'rxjs'
import { catchError, switchMap } from 'rxjs/operators'
import { Store } from './store'
import { DBCache, Http } from './types'
import { RPCError } from './source/ws-source'
import { Source } from './source/source'

export class PatchDB<T> {
  public store: Store<T> = new Store(this.http, this.initialCache)
  public connectionError$ = new Subject<Error>()
  public rpcError$ = new Subject<RPCError>()
  public cache$ = new ReplaySubject<DBCache<T>>(1)

  private sub = this.sources$
    .pipe(
      switchMap(sources =>
        merge(...sources.map(s => s.watch$(this.store))).pipe(
          catchError(e => {
            this.connectionError$.next(e)

            return EMPTY
          }),
        ),
      ),
    )
    .subscribe(res => {
      if ('result' in res) {
        this.store.update(res.result)
        this.cache$.next(this.store.cache)
      } else {
        this.rpcError$.next(res)
      }
    })

  constructor(
    private readonly sources$: Observable<Source<T>[]>,
    private readonly http: Http<T>,
    private readonly initialCache: DBCache<T>,
  ) {}

  clean() {
    this.sub.unsubscribe()
  }
}