import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
import { at, first, fmap, last, second, third } from "./iterables.ts";

Deno.test("at", () => {
  const second = at(1);
  assertEquals(second([1, 4, 8]), 4);
  assertEquals(second([1]), undefined);

  const second_from_end = at(-2);
  assertEquals(second_from_end([1, 4, 6, 8]), 6);
  assertEquals(second_from_end([1]), undefined);
});

Deno.test("first", () => {
  assertEquals(first([1, 4, 8]), 1);
  assertEquals(first([1]), 1);
  assertEquals(first([]), undefined);
});

Deno.test("second", () => {
  assertEquals(second([1, 4, 8]), 4);
  assertEquals(second([1]), undefined);
  assertEquals(second([]), undefined);
});

Deno.test("third", () => {
  assertEquals(third([1, 4, 8]), 8);
  assertEquals(third([1, 4]), undefined);
  assertEquals(third([]), undefined);
});

Deno.test("last", () => {
  assertEquals(last([1, 4, 8]), 8);
  assertEquals(last([1]), 1);
  assertEquals(last([]), undefined);
});

Deno.test("fmap", () => {
  assertEquals(fmap()([1, 2, 3]), [1, 2, 3]);
  assertEquals(fmap((x: number) => x * 2)([1, 2, 3]), [2, 4, 6]);
  assertEquals(fmap(undefined, (x: number) => x % 2 == 0)([1, 2, 3]), [2]);
  assertEquals(fmap((x: number) => x * 2)([1, 2, 3]), [2, 4, 6]);
  assertEquals(
    fmap((x: number) => x * 2, (x: number) => x < 5)([1, 2, 3]),
    [2, 4],
  );
});