import { describe, it, expect } from "vitest";
import { localDateTimeToUtcIso } from "../date-utils";

describe("localDateTimeToUtcIso", () => {
  it("returns null for empty string", () => {
    expect(localDateTimeToUtcIso("")).toBeNull();
  });

  it("returns null for null", () => {
    expect(localDateTimeToUtcIso(null)).toBeNull();
  });

  it("returns null for undefined", () => {
    expect(localDateTimeToUtcIso(undefined)).toBeNull();
  });

  it("returns null for an invalid date string", () => {
    expect(localDateTimeToUtcIso("not-a-date")).toBeNull();
  });

  it("converts a valid datetime-local value and round-trips correctly", () => {
    // The input matches the datetime-local format "YYYY-MM-DDTHH:MM".
    // Regardless of timezone, the resulting ISO string should parse back
    // to the same moment in time.
    const input = "2026-03-11T17:00";
    const result = localDateTimeToUtcIso(input);
    expect(result).not.toBeNull();
    expect(new Date(result!).getTime()).toBe(new Date(input).getTime());
  });

  it("returns a string ending with 'Z' (UTC designator)", () => {
    const result = localDateTimeToUtcIso("2026-03-11T10:00");
    expect(result).not.toBeNull();
    expect(result!.endsWith("Z")).toBe(true);
  });

  it("returns a full ISO-8601 string with milliseconds", () => {
    const result = localDateTimeToUtcIso("2026-06-15T08:30");
    expect(result).not.toBeNull();
    // toISOString() always produces "YYYY-MM-DDTHH:MM:SS.mmmZ"
    expect(result).toMatch(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$/);
  });

});