import {
  Observer,
  Event,
  isValue,
  Observable,
  ObservableSeed,
  Desc,
  Description,
} from "./abstractions"

export function duplicateSkippingObserver<V>(
  initial: V,
  observer: Observer<Event<V>>
) {
  let current = initial
  return (event: Event<V>) => {
    if (isValue(event)) {
      if (event.value !== current) {
        current = event.value
        observer(event)
      }
    } else {
      observer(event)
    }
  }
}

export function nop() {}

export function remove<A>(xs: A[], x: A) {
  for (let i = 0; i < xs.length; i++) {
    if (xs[i] === x) {
      xs.splice(i, 1)
      return
    }
  }
}

export function rename<A extends ObservableSeed<any, any, any>>(
  desc: Desc,
  observable: A
): A {
  observable.desc = new Description(desc)
  return observable
}

export * from "./tostring"