import { atom, bus, map, filter, globalScope, never, toProperty } from "./index"
import { expectPropertyEvents, expectStreamEvents, series } from "./test-utils"
const lessThan = (n: number) => (x: number) => x < n

describe("EventStream.filter", function () {
  describe("should filter values", () =>
    expectStreamEvents(() => {
      const e = series(1, [1, 2, 3]).pipe(filter(lessThan(3)))
      return e
    }, [1, 2]))
  it("toString", () =>
    expect(filter(() => false)(never()).toString()).toEqual(
      "EventStreamSeed never.filter(fn)"
    ))
})

describe("Property.filter", function () {
  describe("should filter values", () =>
    expectPropertyEvents(() => {
      const prop = series(1, [1, 2, 3]).pipe(toProperty(0), filter(lessThan(3)))
      return prop
    }, [0, 1, 2]))
  it("preserves old current value if the updated value is non-matching", function () {
    const a = atom(1)
    const p = a.pipe(map((x: number) => x))
    const fp = p.pipe(filter(lessThan(2), globalScope))
    a.set(2)
    expect(fp.get()).toEqual(1)
  })
})

describe("Atom.filter", () => {
  describe("Root atom", () => {
    it("Freezes on unwanted values", () => {
      const root = atom<string | null>("hello")
      const a = root.pipe(filter((a) => a !== null, globalScope))

      a.set("world")
      expect(a.get()).toEqual("world")
      a.set(null)
      expect(a.get()).toEqual("world")
      expect(root.get()).toEqual(null) // pass all values in set
      a.set("hello")
      expect(a.get()).toEqual("hello")
      expect(root.get()).toEqual("hello")
    })

    it("Freezes on unwanted values (when not getting in between sets)", () => {
      const a = filter(
        (a) => a !== null,
        globalScope
      )(atom<string | null>("hello"))

      a.set("world")
      a.set(null)
      expect(a.get()).toEqual("world")
    })
  })

  describe("Dependent atom", () => {
    it("Freezes on unwanted values", () => {
      const b = bus<string | null>()
      const prop = toProperty("1", globalScope)(b)
      const root = atom(prop, (newValue) => b.push(newValue))
      const a = filter((a) => a !== null, globalScope)(root)

      a.set("world")
      expect(a.get()).toEqual("world")
      a.set(null)
      expect(a.get()).toEqual("world")
    })

    it("Freezes on unwanted values (when not getting in between sets)", () => {
      const b = bus<string | null>()
      const prop = toProperty("1", globalScope)(b)
      const root = atom(prop, (newValue) => b.push(newValue))
      const a = filter((a) => a !== null, globalScope)(root)

      a.set("world")
      a.set(null)
      expect(a.get()).toEqual("world")
    })
  })
})