selector.ts

import * as memoize from 'memoize'
import { Observable } from 'rxjs/Observable'
import 'rxjs/add/operator/share'
import 'rxjs/add/operator/distinctUntilChanged'

export interface Selector<T,V> {
  ( source$: Observable<T> ): Observable<V>
}

export interface SelectorFactory<T,V> {
   ( ...args: any[] ): Selector<T,V>
}

export function publishDistinct<T,V>(
  source$: Observable<T>,
  selectorFactory: SelectorFactory<T,V>
): (...args: any[]) => Observable<V> {
  return memoize(
    ( ...args: any[] ) => selectorFactory( ...args )( source$ )
      .distinctUntilChanged()
      .share()
  )
}