import { describe, expect, it } from 'vitest';
import MonthSelector, {
  formatMonth,
  generateMonthOptions
} from '../../src/lib/components/layout/MonthSelector.svelte';
import { selectedPeriod, setPeriod } from '../../src/lib/stores/period';

function getStoreValue<T>(store: { subscribe: (run: (value: T) => void) => () => void }): T {
  let value!: T;
  const unsubscribe = store.subscribe((current) => {
    value = current;
  });
  unsubscribe();
  return value;
}

describe('MonthSelector component', () => {
  it('exports a component module', () => {
    expect(MonthSelector).toBeDefined();
  });

  it('formats month labels', () => {
    expect(formatMonth('2026-02')).toBe('Feb 2026');
  });

  it('builds +/- 6 month options', () => {
    const options = generateMonthOptions(new Date(2026, 1, 1));
    expect(options).toHaveLength(13);
    expect(options[0]).toBe('2025-08');
    expect(options[12]).toBe('2026-08');
  });

  it('selection updates period store', () => {
    setPeriod('2026-02');
    expect(getStoreValue(selectedPeriod)).toBe('2026-02');
  });
});