import { describe, expect, it } from "vitest";

import { lazy } from "./lazy";

describe("lazy", () => {
  it("lazy value returned when get is called", () => {
    const value = lazy(() => "value");

    expect(value.get()).toBe("value");
  });

  it("lazy function not called if get isn't called", () => {
    let setValue = false;
    lazy(() => {
      setValue = true;
      return "value";
    });

    expect(setValue).toBe(false);
  });

  it("lazy function called if get is called", () => {
    let setValue = false;
    lazy(() => {
      setValue = true;
      return "value";
    }).get();

    expect(setValue).toBe(true);
  });

  it("lazy function called only once if get is called multiple times", () => {
    let count = 0;
    const value = lazy(() => {
      count++;
      return "value";
    });
    const NUM_TIMES_CALLED = 1_000_000;
    for (let i = 0; i < NUM_TIMES_CALLED; i++) {
      value.get();
    }

    expect(count).toBe(1);
  });
});