import { describe, it, expect, beforeEach, vi } from "vitest";
import {
  defaultCartesReferencePeriod,
  readCartesPeriodMode,
  CARTES_PERIOD_MODE_STORAGE_KEY,
} from "./useCartes";

describe("defaultCartesReferencePeriod", () => {
  it("returns the month before the given date", () => {
    expect(defaultCartesReferencePeriod(new Date(2026, 3, 15))).toEqual({
      year: 2026,
      month: 3,
    });
  });

  it("wraps around January to December of the previous year", () => {
    expect(defaultCartesReferencePeriod(new Date(2026, 0, 10))).toEqual({
      year: 2025,
      month: 12,
    });
  });

  it("handles the last day of a month", () => {
    expect(defaultCartesReferencePeriod(new Date(2026, 5, 30))).toEqual({
      year: 2026,
      month: 5,
    });
  });
});

describe("readCartesPeriodMode (localStorage round-trip)", () => {
  const store = new Map<string, string>();
  const mockLocalStorage = {
    getItem: vi.fn((key: string) => store.get(key) ?? null),
    setItem: vi.fn((key: string, value: string) => {
      store.set(key, value);
    }),
    removeItem: vi.fn((key: string) => {
      store.delete(key);
    }),
    clear: vi.fn(() => store.clear()),
    key: vi.fn(),
    length: 0,
  };

  beforeEach(() => {
    store.clear();
    vi.stubGlobal("localStorage", mockLocalStorage);
  });

  it("defaults to 'month' when nothing is persisted", () => {
    expect(readCartesPeriodMode()).toBe("month");
  });

  it("reads back a previously persisted 'month' value (round-trip)", () => {
    store.set(CARTES_PERIOD_MODE_STORAGE_KEY, "month");
    expect(readCartesPeriodMode()).toBe("month");
  });

  it("reads back a previously persisted 'ytd' value (round-trip)", () => {
    store.set(CARTES_PERIOD_MODE_STORAGE_KEY, "ytd");
    expect(readCartesPeriodMode()).toBe("ytd");
  });

  it("falls back to default for unknown/corrupted values", () => {
    store.set(CARTES_PERIOD_MODE_STORAGE_KEY, "bogus");
    expect(readCartesPeriodMode()).toBe("month");
  });

  it("supports a custom fallback", () => {
    expect(readCartesPeriodMode(CARTES_PERIOD_MODE_STORAGE_KEY, "ytd")).toBe("ytd");
  });

  it("uses the expected storage key", () => {
    expect(CARTES_PERIOD_MODE_STORAGE_KEY).toBe("reports-cartes-period-mode");
  });
});