import {
  EventStream,
  EventStreamSeed,
  isEventStream,
  isProperty,
  isPropertySeed,
  Observer,
  Property,
  PropertySeed,
  Scope,
  Subscribe,
} from "./abstractions"
import { applyScopeMaybe } from "./applyscope"
import { mapSubscribe } from "./map"
import { PropertySeedImpl, StatelessProperty } from "./property"
import { globalScope } from "./scope"

export interface ToStatelessPropertyOp<A> {
  (stream: EventStream<any> | Subscribe<any>): Property<A>
}
export function toStatelessProperty<A>(get: () => A): ToStatelessPropertyOp<A>
export function toStatelessProperty<A>(get: () => A) {
  return (streamOrSubscribe: any) => {
    if (isEventStream(streamOrSubscribe)) {
      return new StatelessProperty(
        streamOrSubscribe.desc,
        get,
        mapSubscribe(streamOrSubscribe.subscribe.bind(streamOrSubscribe), get),
        streamOrSubscribe.getScope()
      )
    } else {
      return new StatelessProperty(
        [streamOrSubscribe, "toStatelessProperty", [get]],
        get,
        mapSubscribe(streamOrSubscribe, get),
        globalScope
      )
    }
  }
}

export interface ToPropertyOp<A> {
  <B>(stream: EventStream<B> | EventStreamSeed<B>): PropertySeed<A | B>
}
export interface ToPropertyOpScoped<A> {
  <B>(stream: EventStream<B> | EventStreamSeed<B>): Property<A | B>
}

export function toProperty<A>(initial: A): ToPropertyOp<A>
export function toProperty<A>(initial: A, scope: Scope): ToPropertyOpScoped<A>
export function toProperty(initial: any, scope?: Scope) {
  return (seed: EventStream<any> | EventStreamSeed<any>) => {
    const source = seed.consume()
    return applyScopeMaybe(
      new PropertySeedImpl(
        [seed, "toProperty", [initial]],
        () => initial,
        (onValue, onEnd) => {
          return source.subscribe(onValue, onEnd)
        }
      ),
      scope
    )
  }
}

export function toPropertySeed<A>(
  property: Property<A> | PropertySeed<A>
): PropertySeed<A> {
  if (!isProperty(property)) {
    if (!isPropertySeed(property)) {
      throw Error("Assertion fail")
    }
    return property
  }
  return new PropertySeedImpl<A>(
    property.desc,
    property.get.bind(property),
    property.onChange.bind(property)
  )
}