import {
  Event,
  EventLike,
  EventStream,
  EventStreamSeed,
  isEnd,
  isValue,
  Observer,
  Scope,
  Subscribe,
  toEvents,
  Unsub,
} from "./abstractions"
import { applyScopeMaybe } from "./applyscope"
import { EventStreamSeedImpl } from "./eventstream"
import { nop } from "./util"

export function fromSubscribe<V>(subscribe: Subscribe<V>): EventStreamSeed<V>
export function fromSubscribe<V>(
  subscribe: Subscribe<V>,
  scope: Scope
): EventStream<V>
export function fromSubscribe<V>(
  subscribe: Subscribe<V>,
  scope?: Scope
): EventStream<V> | EventStreamSeed<V> {
  return applyScopeMaybe(
    new EventStreamSeedImpl("fromSubscribe(fn)", subscribe),
    scope
  )
}

export type FlexibleObserver<V> = (event: EventLike<V>) => void
export type FlexibleSubscribe<V> = (observer: FlexibleObserver<V>) => Unsub

export function toFlexibleObserver<V>(
  onValue: Observer<V>,
  onEnd: Observer<void> = nop
): FlexibleObserver<V> {
  return (eventLike: EventLike<V>) => {
    const events = toEvents(eventLike)
    for (const event of events) {
      if (isValue(event)) {
        onValue(event.value)
      } else {
        onEnd()
        return
      }
    }
  }
}

export function fromFlexibleSubscibe<V>(
  subscribe: FlexibleSubscribe<V>
): EventStreamSeed<V>
export function fromFlexibleSubscibe<V>(
  subscribe: FlexibleSubscribe<V>,
  scope: Scope
): EventStream<V>
export function fromFlexibleSubscibe<V>(
  subscribe: FlexibleSubscribe<V>,
  scope?: Scope
): EventStream<V> | EventStreamSeed<V> {
  return applyScopeMaybe(
    new EventStreamSeedImpl("fromSubscribe(fn)", (onValue, onEnd) =>
      subscribe(toFlexibleObserver(onValue, onEnd))
    ),
    scope
  )
}