import { expect, test } from '@playwright/test';

/**
 * Track Q Q4: currency switch must recalculate by FX quote. Explicitly,
 * "160 RUB" must not become "160 USD" - the number has to change, not just
 * the label next to it.
 *
 * Written before the checkout money-truth rewrite (frontend backlog F10-F16,
 * which deletes CurrencyRatesService's client-side float math and switches
 * checkout to a server-computed total per
 * docs/backend/PHASE-1-MONEY-FX-PAYMENTS-CONTRACT.md §5). This test exists so
 * that rewrite has something to break loudly if it silently stops converting.
 */
test.describe('currency switch', () => {
  test('switching currency changes the displayed price value, not just its label', async ({ page }) => {
    await page.goto('/');
    await page.waitForLoadState('networkidle');

    const priceLocator = page.locator('.current-price, .original-price').first();
    await expect(priceLocator).toBeVisible({ timeout: 15_000 });

    const before = await readPrice(priceLocator);
    expect(before.value, 'a price must be a real positive number before switching').toBeGreaterThan(0);

    await switchCurrency(page, before.currency === 'USD' ? 'RUB' : 'USD');

    // The pipe is `pure: false` and re-evaluates on the next change-detection
    // cycle; give the DOM a moment to actually repaint rather than reading
    // stale text off a signal that hasn't propagated yet.
    await expect
      .poll(async () => (await priceLocator.textContent()) ?? '')
      .not.toContain(before.currency);

    const after = await readPrice(priceLocator);

    expect(after.currency, 'the currency label must actually change').not.toBe(before.currency);
    // The literal regression this test exists to catch: a rate of 1 disguised
    // as a real conversion. RUB->USD or USD->RUB is never a 1:1 rate.
    expect(after.value, `${before.value} ${before.currency} must not equal ${after.value} ${after.currency}`).not.toBeCloseTo(before.value, 2);
  });

  test('an out-of-range rate must not silently pass as valid', async ({ page }) => {
    // Guards the specific bad-data class this suite exists to catch: a
    // conversion that returns something implausible (zero, negative, or
    // absurdly large) instead of erroring visibly.
    await page.goto('/');

    const priceLocator = page.locator('.current-price, .original-price').first();
    await expect(priceLocator).toBeVisible({ timeout: 15_000 });

    const { value } = await readPrice(priceLocator);

    expect(value).toBeGreaterThan(0);
    expect(value).toBeLessThan(100_000_000);
  });
});

async function switchCurrency(page: import('@playwright/test').Page, targetCode: string): Promise<void> {
  // The page renders more than one language-selector instance (desktop/mobile
  // variants share the same markup) - scoping to the dropdown that actually
  // carries the "open" class avoids clicking an option in a hidden duplicate,
  // which is silently a no-op rather than a failure.
  const trigger = page.locator('.currency-button:visible').first();
  await trigger.click();

  const openDropdown = page.locator('.currency-dropdown.open').first();
  await expect(openDropdown).toBeVisible();

  await openDropdown.locator('.currency-option', { hasText: targetCode }).first().click();
}

async function readPrice(locator: import('@playwright/test').Locator): Promise<{ value: number; currency: string }> {
  const text = (await locator.textContent()) ?? '';
  // Matches "1 234.56 USD" / "1234.56 ₽" shapes the price templates render.
  const match = text.replace(/\s/g, '').match(/([\d.,]+)([A-Z]{3}|\D+)$/);
  if (!match) {
    throw new Error(`could not parse price text: "${text}"`);
  }
  const value = Number(match[1].replace(/,/g, ''));
  return { value, currency: match[2] };
}