import { assertEquals, test } from "Test"
import { Just, Nothing } from "Maybe"
import { apL, liftA2, liftA3 } from "./Applicative"

// apL
test("apL - Maybe Just", () => pipe(
  apL($, Just(2)),
  assertEquals($, Just(1)),
)(Just(1)))

test("apL - Maybe Nothing first", () => assertEquals(apL(Nothing, Just(2)), Nothing))
test("apL - Maybe Nothing second", () => assertEquals(apL(Just(1), Nothing), Nothing))

test("apL - List", () => assertEquals(apL([1, 2], [3, 4]), [1, 1, 2, 2]))

// liftA2
test("liftA2 - Maybe", () => pipe(
  liftA2((a, b) => a + b, Just(2)),
  assertEquals($, Just(5)),
)(Just(3)))

test("liftA2 - Maybe Nothing", () => assertEquals(
  liftA2((a, b) => a + b, Nothing, Just(3)),
  Nothing,
))

test("liftA2 - List", () => assertEquals(
  liftA2((a, b) => a + b, [1, 2], [10, 20]),
  [11, 21, 12, 22],
))

// liftA3
test("liftA3 - Maybe", () => pipe(
  liftA3((a, b, c) => a + b + c, Just(1), Just(2)),
  assertEquals($, Just(6)),
)(Just(3)))

test("liftA3 - Maybe Nothing", () => assertEquals(
  liftA3((a, b, c) => a + b + c, Just(1), Nothing, Just(3)),
  Nothing,
))

// Applicative laws - identity
test("ap identity - Maybe", () => assertEquals(
  ap(Just((x) => x), Just(3)),
  Just(3),
))

// Applicative laws - homomorphism
test("ap homomorphism - Maybe", () => assertEquals(
  ap(Just((x) => x + 1), Just(3)),
  Just(4),
))