flatmaplatest.ts

import {
  Scope,
  EventStream,
  EventStreamSeed,
  isPropertySeed,
  Observable,
  Property,
  PropertySeed,
} from "./abstractions"
import { applyScopeMaybe } from "./applyscope"
import { FlatMapStreamSeed, FlatMapPropertySeed, Spawner } from "./flatmap"
import { BinaryTransformOp, BinaryTransformOpScoped } from "./transform"

// TODO: typing is not perfect: spawners for properties should spawn property(seed)s, not streams

export function flatMapLatest<A, B>(
  fn: Spawner<
    A,
    PropertySeed<B> | Property<B> | EventStream<B> | EventStreamSeed<B>
  >
): BinaryTransformOp<A, B>
export function flatMapLatest<A, B>(
  fn: Spawner<
    A,
    PropertySeed<B> | Property<B> | EventStream<B> | EventStreamSeed<B>
  >,
  scope: Scope
): BinaryTransformOpScoped<A, B>

export function flatMapLatest<A>(fn: Spawner<A, any>, scope?: Scope): any {
  return (s: any) => {
    if (isPropertySeed<A>(s)) {
      return applyScopeMaybe(
        new FlatMapPropertySeed([s, "flatMapLatest", [fn]], s, fn, {
          latest: true,
        }),
        scope
      )
    } else {
      return applyScopeMaybe(
        new FlatMapStreamSeed([s, "flatMapLatest", [fn]], s, fn, {
          latest: true,
        }),
        scope
      )
    }
  }
}