import { getNavigationSource } from '@/lib/analytics';

/** jsdom's document.referrer is read-only; redefining it is the way in. */
function referrer(url: string) {
  Object.defineProperty(document, 'referrer', { value: url, configurable: true });
}

const ORIGIN = 'http://localhost';

describe('getNavigationSource', () => {
  afterEach(() => referrer(''));

  it('attributes a visit from a location page to the place layer', () => {
    /*
     * The one this was added for.
     *
     * W2 published ~3,900 location pages whose entire purpose is to funnel
     * search traffic onto school pages. Before this case existed they fell
     * through to 'direct' — so the location layer's contribution was not
     * merely missing from the funnel, it was being counted in the bucket you
     * read as "typed the URL". The measurement that decides whether W2 worked
     * was confidently reporting the wrong answer.
     */
    referrer(`${ORIGIN}/schools/barnet`);
    expect(getNavigationSource()).toBe('place');
  });

  it.each([
    ['/schools/authority/kent', 'authority'],
    ['/schools/near/sw11', 'outcode'],
    ['/schools/brentwood/primary', 'phase variant'],
  ])('covers %s (%s)', (path) => {
    referrer(`${ORIGIN}${path}`);
    expect(getNavigationSource()).toBe('place');
  });

  it('still calls a school page "detail", one character away', () => {
    // /school/ and /schools/ differ by one letter and mean different things.
    // A prefix test written in the wrong order silently merges them.
    referrer(`${ORIGIN}/school/100010-brecknock-primary-school`);
    expect(getNavigationSource()).toBe('detail');
  });

  it.each([
    ['/', 'search'],
    ['/rankings', 'rankings'],
    ['/compare?urns=1,2', 'compare'],
  ])('leaves %s attributed as %s', (path, expected) => {
    referrer(`${ORIGIN}${path}`);
    expect(getNavigationSource()).toBe(expected);
  });

  it('treats an external referrer as direct', () => {
    // Umami records the real referrer on the pageview; this field is only
    // about internal navigation.
    referrer('https://www.google.com/search?q=schools+in+barnet');
    expect(getNavigationSource()).toBe('direct');
  });

  it('treats no referrer as direct', () => {
    referrer('');
    expect(getNavigationSource()).toBe('direct');
  });
});