import { afterAll, afterEach, beforeAll, describe, expect, it, vi } from "vitest";
import { toApiDate, toLocalIsoDate, todayLocalIsoDate } from "./dates";

/**
 * The beekeeper's phone runs in Europe/Berlin. Between 00:00 and 02:00 local
 * time (01:00 in winter) the UTC date is still yesterday - a form opened then
 * must still prefill today's date.
 */
describe("local calendar dates", () => {
  const originalTz = process.env.TZ;

  beforeAll(() => {
    process.env.TZ = "Europe/Berlin";
  });

  afterAll(() => {
    process.env.TZ = originalTz;
  });

  afterEach(() => {
    vi.useRealTimers();
  });

  it("returns today's local date shortly after midnight in summer time", () => {
    vi.useFakeTimers();
    // 00:30 CEST on 12.10.2026 is still 11.10. in UTC.
    vi.setSystemTime(new Date("2026-10-11T22:30:00.000Z"));

    expect(todayLocalIsoDate()).toBe("2026-10-12");
  });

  it("returns today's local date shortly after midnight in winter time", () => {
    vi.useFakeTimers();
    // 00:15 CET on 16.01.2027 is still 15.01. in UTC.
    vi.setSystemTime(new Date("2027-01-15T23:15:00.000Z"));

    expect(todayLocalIsoDate()).toBe("2027-01-16");
  });

  it("keeps the date late in the evening", () => {
    vi.useFakeTimers();
    vi.setSystemTime(new Date("2026-10-12T21:59:00.000Z")); // 23:59 CEST

    expect(todayLocalIsoDate()).toBe("2026-10-12");
  });

  it("formats any date by its local calendar day with zero padding", () => {
    expect(toLocalIsoDate(new Date(2026, 0, 5, 0, 10))).toBe("2026-01-05");
    expect(toLocalIsoDate(new Date(2026, 11, 31, 23, 59))).toBe("2026-12-31");
  });

  it("sends a picked calendar day as midnight UTC of that same day", () => {
    expect(toApiDate("2026-10-12")).toBe("2026-10-12T00:00:00.000Z");
    expect(toApiDate("2027-01-01")).toBe("2027-01-01T00:00:00.000Z");
  });

  it("keeps the picked day on a phone far from UTC", () => {
    process.env.TZ = "Pacific/Auckland";
    try {
      expect(toApiDate("2026-10-12")).toBe("2026-10-12T00:00:00.000Z");
    } finally {
      process.env.TZ = "Europe/Berlin";
    }
  });

  it("refuses something that is not a calendar day instead of sending a wrong date", () => {
    expect(() => toApiDate("")).toThrow();
    expect(() => toApiDate("12.10.2026")).toThrow();
    expect(() => toApiDate("2026-02-30")).toThrow();
  });
});