/**
 * Unit tests for i18n: getLang, t (fallback, params), monthName.
 */

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

const mockGetInitData = vi.fn();
vi.mock("./auth.js", () => ({ getInitData: () => mockGetInitData() }));

import { getLang, t, monthName, MESSAGES } from "./i18n.js";

describe("getLang", () => {
  const origNavigator = globalThis.navigator;

  beforeEach(() => {
    mockGetInitData.mockReset();
  });

  it("returns lang from initData user when present", () => {
    mockGetInitData.mockReturnValue(
      "user=" + encodeURIComponent(JSON.stringify({ language_code: "en" }))
    );
    expect(getLang()).toBe("en");
  });

  it("normalizes ru from initData", () => {
    mockGetInitData.mockReturnValue(
      "user=" + encodeURIComponent(JSON.stringify({ language_code: "ru" }))
    );
    expect(getLang()).toBe("ru");
  });

  it("falls back to navigator.language when initData empty", () => {
    mockGetInitData.mockReturnValue("");
    Object.defineProperty(globalThis, "navigator", {
      value: { ...origNavigator, language: "en-US", languages: ["en-US", "en"] },
      configurable: true,
    });
    expect(getLang()).toBe("en");
  });

  it("normalizes to en for unknown language code", () => {
    mockGetInitData.mockReturnValue(
      "user=" + encodeURIComponent(JSON.stringify({ language_code: "uk" }))
    );
    expect(getLang()).toBe("en");
  });
});

describe("t", () => {
  it("returns translation for existing key", () => {
    expect(t("en", "app.title")).toBe("Duty Calendar");
    expect(t("ru", "app.title")).toBe("Календарь дежурств");
  });

  it("falls back to en when key missing in lang", () => {
    expect(t("ru", "app.title")).toBe("Календарь дежурств");
    expect(t("en", "loading")).toBe("Loading…");
  });

  it("returns key when key missing in both", () => {
    expect(t("en", "missing.key")).toBe("missing.key");
    expect(t("ru", "unknown")).toBe("unknown");
  });

  it("replaces params placeholder", () => {
    expect(t("en", "duty.until", { time: "14:00" })).toBe("until 14:00");
    expect(t("ru", "duty.until", { time: "09:30" })).toBe("до 09:30");
  });

  it("handles empty params", () => {
    expect(t("en", "loading", {})).toBe("Loading…");
  });
});

describe("monthName", () => {
  it("returns month name for 0-based index", () => {
    expect(monthName("en", 0)).toBe("January");
    expect(monthName("en", 11)).toBe("December");
    expect(monthName("ru", 0)).toBe("Январь");
  });

  it("returns empty string for out-of-range", () => {
    expect(monthName("en", 12)).toBe("");
    expect(monthName("en", -1)).toBe("");
  });
});