import { test, expect, type Page } from './fixtures';

// As the reader nears the end of a chapter, the next chapter's first page
// images are prefetched (hidden) so flipping over is instant. They must NOT
// be present at the start of the chapter.

const MANGA_ID = 'm1';
const CH1 = 'c1';
const CH2 = 'c2';
const CH3 = 'c3';

function pages(prefix: string, n: number) {
    return Array.from({ length: n }, (_, i) => ({
        id: `${prefix}p${i + 1}`,
        chapter_id: prefix,
        page_number: i + 1,
        storage_key: `${prefix}/${i + 1}`,
        content_type: 'image/svg+xml'
    }));
}

function chapter(id: string, number: number, count: number) {
    return { id, manga_id: MANGA_ID, number, title: null, page_count: count, created_at: `2026-0${number}-01T00:00:00Z`, size_bytes: 0 };
}

async function mockReader(page: Page) {
    await page.route('**/api/v1/**', async (route) => {
        const { pathname } = new URL(route.request().url());
        const json = (status: number, body: unknown) =>
            route.fulfill({ status, contentType: 'application/json', body: JSON.stringify(body) });

        if (pathname.includes('/files/')) {
            return route.fulfill({ status: 200, contentType: 'image/svg+xml', body: '<svg xmlns="http://www.w3.org/2000/svg" width="800" height="1000"/>' });
        }
        if (pathname.endsWith('/auth/config')) return json(200, { self_register_enabled: true, private_mode: false });
        if (pathname.endsWith('/auth/me')) return json(401, { error: { code: 'unauthenticated', message: 'no' } });
        if (pathname.endsWith('/auth/me/preferences')) return json(401, { error: { code: 'unauthenticated', message: 'no' } });
        if (pathname.endsWith(`/chapters/${CH1}/pages`)) return json(200, { pages: pages(CH1, 5) });
        if (pathname.endsWith(`/chapters/${CH2}/pages`)) return json(200, { pages: pages(CH2, 4) });
        if (pathname.endsWith(`/chapters/${CH3}/pages`)) return json(200, { pages: pages(CH3, 3) });
        if (pathname.endsWith(`/chapters/${CH1}`)) return json(200, chapter(CH1, 1, 5));
        if (pathname.endsWith(`/chapters/${CH2}`)) return json(200, chapter(CH2, 2, 4));
        if (pathname.endsWith(`/chapters/${CH3}`)) return json(200, chapter(CH3, 3, 3));
        if (pathname.includes(`/mangas/${MANGA_ID}/chapters`)) {
            // Oldest-first, as the reader expects (next = index + 1).
            return json(200, { items: [chapter(CH1, 1, 5), chapter(CH2, 2, 4), chapter(CH3, 3, 3)], page: { limit: 200, offset: 0, total: 3 } });
        }
        if (pathname.endsWith(`/mangas/${MANGA_ID}`)) return json(200, { id: MANGA_ID, title: 'Berserk', status: 'ongoing', alt_titles: [], description: null, cover_image_path: null, created_at: '2026-01-01T00:00:00Z', updated_at: '2026-01-01T00:00:00Z', authors: [], genres: [], tags: [], content_warnings: [], chapter_storage_bytes: 0 });
        if (pathname.includes('/me/read-progress')) return json(401, { error: { code: 'unauthenticated', message: 'no' } });
        return json(503, { error: { code: 'e2e_unmocked', message: pathname } });
    });
}

test('prefetches the next chapter first pages only when near the end', async ({ page }) => {
    await mockReader(page);
    await page.goto(`/manga/${MANGA_ID}/chapter/${CH1}`);
    await expect(page.getByTestId('reader-page')).toBeVisible();

    // Start of a 5-page chapter → not near the end → no next-chapter preload.
    await expect(page.getByTestId('reader-next-preload')).toHaveCount(0);

    // Jump to the last page.
    await page.keyboard.press('End');

    // Next chapter's first pages are now prefetched.
    const preloads = page.getByTestId('reader-next-preload');
    await expect(preloads.first()).toBeAttached();
    await expect(preloads).toHaveCount(3);
    await expect(preloads.first()).toHaveAttribute('src', /c2\/1/);
});

test('clears stale prefetch when navigating to the next chapter', async ({ page }) => {
    await mockReader(page);
    await page.goto(`/manga/${MANGA_ID}/chapter/${CH1}`);
    await expect(page.getByTestId('reader-page')).toBeVisible();

    // Warm chapter 2's pages near the end of chapter 1.
    await page.keyboard.press('End');
    await expect(page.getByTestId('reader-next-preload')).toHaveCount(3);

    // Navigate to chapter 2. At its start (not near the end) the previous
    // prefetch must be cleared, even though chapter 2 has its own next (3).
    await page.goto(`/manga/${MANGA_ID}/chapter/${CH2}`);
    await expect(page.getByTestId('reader-page')).toBeVisible();
    await expect(page.getByTestId('reader-next-preload')).toHaveCount(0);
});