import { describe, it, expect } from "vitest";
import { formatDate, toDateInputValue } from "./format-date";
import { EMPTY } from "./placeholder";

describe("formatDate", () => {
  it("returns the canonical EMPTY placeholder for null/undefined/empty", () => {
    expect(formatDate(null)).toBe(EMPTY);
    expect(formatDate(undefined)).toBe(EMPTY);
    expect(formatDate("")).toBe(EMPTY);
  });

  it("parses a bare YYYY-MM-DD as a local-tz date (no UTC off-by-one)", () => {
    // The whole point of the helper: a stored "2026-05-03" must render as the
    // 3rd in every timezone, matching a Date built from local year/month/day —
    // not shift to the 2nd west of UTC the way `new Date("2026-05-03")` would.
    const expected = new Date(2026, 4, 3).toLocaleDateString(undefined, {
      month: "short",
      day: "numeric",
      year: "numeric",
    });
    expect(formatDate("2026-05-03", "medium")).toBe(expected);
  });

  it("accepts a Date instance", () => {
    const expected = new Date(2026, 4, 3).toLocaleDateString(undefined, {
      month: "short",
      day: "numeric",
      year: "numeric",
    });
    expect(formatDate(new Date(2026, 4, 3), "medium")).toBe(expected);
  });

  it("defaults to the medium style", () => {
    expect(formatDate("2026-05-03")).toBe(formatDate("2026-05-03", "medium"));
  });

  it("supports short and long styles", () => {
    expect(formatDate("2026-05-03", "short")).toBe(
      new Date(2026, 4, 3).toLocaleDateString(undefined, {
        month: "numeric",
        day: "numeric",
        year: "2-digit",
      }),
    );
    expect(formatDate("2026-05-03", "long")).toBe(
      new Date(2026, 4, 3).toLocaleDateString(undefined, {
        weekday: "long",
        month: "long",
        day: "numeric",
        year: "numeric",
      }),
    );
  });

  it("includes the time for the datetime style", () => {
    // ISO datetimes keep their time component. Compare against the same
    // toLocaleString options the helper uses so the assertion stays
    // locale-agnostic (no reliance on ASCII digits or a fixed format).
    const iso = "2026-05-03T15:45:00Z";
    const expected = new Date(iso).toLocaleString(undefined, {
      month: "short",
      day: "numeric",
      year: "numeric",
      hour: "numeric",
      minute: "2-digit",
    });
    expect(formatDate(iso, "datetime")).toBe(expected);
  });

  it("returns an unparseable string verbatim", () => {
    expect(formatDate("not a date")).toBe("not a date");
  });

  it("returns EMPTY for an invalid Date instance", () => {
    expect(formatDate(new Date("nonsense"))).toBe(EMPTY);
  });
});

describe("toDateInputValue", () => {
  it("returns an empty string for null/undefined/empty", () => {
    expect(toDateInputValue(null)).toBe("");
    expect(toDateInputValue(undefined)).toBe("");
    expect(toDateInputValue("")).toBe("");
  });

  it("passes a bare YYYY-MM-DD through verbatim", () => {
    expect(toDateInputValue("2026-05-03")).toBe("2026-05-03");
  });

  it("returns an unparseable value verbatim", () => {
    expect(toDateInputValue("not a date")).toBe("not a date");
  });
});