import { describe, expect, it } from "vitest";
import { monthLabel, monthRange } from "./monthRange";

describe("monthRange", () => {
  it("returns the first and last day of the base month at offset 0", () => {
    expect(monthRange(0, new Date(2026, 7, 15))).toEqual({ from: "2026-08-01", to: "2026-08-31" });
  });

  it("steps back a month, crossing a year boundary", () => {
    expect(monthRange(-1, new Date(2026, 0, 10))).toEqual({ from: "2025-12-01", to: "2025-12-31" });
  });

  it("steps forward a month, crossing a year boundary", () => {
    expect(monthRange(1, new Date(2025, 11, 20))).toEqual({ from: "2026-01-01", to: "2026-01-31" });
  });

  it("handles a short month (February, non-leap year)", () => {
    expect(monthRange(0, new Date(2026, 1, 1))).toEqual({ from: "2026-02-01", to: "2026-02-28" });
  });

  it("handles a leap-year February", () => {
    expect(monthRange(0, new Date(2028, 1, 1))).toEqual({ from: "2028-02-01", to: "2028-02-29" });
  });
});

describe("monthLabel", () => {
  it("formats as '<year> оны <month>-р сар'", () => {
    expect(monthLabel(0, new Date(2026, 7, 15))).toBe("2026 оны 8-р сар");
  });

  it("rolls the year when stepping across January", () => {
    expect(monthLabel(-1, new Date(2026, 0, 5))).toBe("2025 оны 12-р сар");
    expect(monthLabel(1, new Date(2025, 11, 5))).toBe("2026 оны 1-р сар");
  });
});