import {
    actionLabel,
    activeStatusById,
    applyFilterAndSort,
    countByFilter,
    deriveState,
    downloadProgressPercent,
    formatDownloadBytes,
    formatBytesPerSecond,
    formatDownloadEta,
    formatDownloadSpeed,
    formatDownloadSpeedShort,
    mergeGameUpdate,
} from '../src/lib/gameState.ts';
import {
    ActiveOperationKind,
    GameAvailability,
    InstallStatus,
    type Game,
} from '../src/lib/types.ts';

const assertEquals = <T>(actual: T, expected: T, message: string) => {
    if (actual !== expected) {
        throw new Error(`${message}: expected ${expected}, got ${actual}`);
    }
};

const game = (overrides: Partial<Game> = {}): Game => ({
    id: 'game',
    name: 'Game',
    description: '',
    size: 0,
    downloaded: false,
    installed: false,
    availability: GameAvailability.LocalOnly,
    install_status: InstallStatus.NotInstalled,
    peer_count: 1,
    ...overrides,
});

Deno.test('snapshot keeps installing visible until installed state settles', () => {
    const fromDownloading = game({
        install_status: InstallStatus.Downloading,
    });
    const installing = mergeGameUpdate(
        game({ downloaded: true }),
        fromDownloading,
        InstallStatus.Installing,
    );
    const installedWhileActive = mergeGameUpdate(
        game({ downloaded: true, installed: true }),
        installing,
        InstallStatus.Installing,
    );
    const settled = mergeGameUpdate(
        game({ downloaded: true, installed: true }),
        installedWhileActive,
    );

    assertEquals(
        installing.install_status,
        InstallStatus.Installing,
        'active install snapshot should render Installing',
    );
    assertEquals(
        installedWhileActive.install_status,
        InstallStatus.Installing,
        'installed local state should not override an active install snapshot',
    );
    assertEquals(
        settled.install_status,
        InstallStatus.Installed,
        'cleared active snapshot with installed local state should render Installed',
    );
});

Deno.test('active operation snapshot is the source of busy status', () => {
    const statuses = activeStatusById([
        { id: 'game', operation: ActiveOperationKind.Downloading },
        { id: 'other', operation: ActiveOperationKind.Updating },
    ]);

    assertEquals(
        statuses.get('game'),
        InstallStatus.Downloading,
        'download operation should render Downloading',
    );
    assertEquals(
        statuses.get('other'),
        InstallStatus.Installing,
        'update operation should render Installing',
    );
});

Deno.test('download progress is preserved only while actively downloading', () => {
    const downloading = game({
        install_status: InstallStatus.Downloading,
        download_progress: {
            downloaded_bytes: 50,
            total_bytes: 100,
            bytes_per_second: 12_500_000,
            active_peer_count: 2,
        },
    });

    const stillDownloading = mergeGameUpdate(
        game(),
        downloading,
        InstallStatus.Downloading,
    );
    const settled = mergeGameUpdate(game({ downloaded: true }), stillDownloading);

    assertEquals(
        stillDownloading.download_progress?.downloaded_bytes,
        50,
        'active download snapshot should keep progress',
    );
    assertEquals(
        stillDownloading.download_progress?.active_peer_count,
        2,
        'active download snapshot should keep live peer count',
    );
    assertEquals(
        settled.download_progress,
        undefined,
        'settled snapshot should clear progress',
    );
});

Deno.test('downloading action label includes current speed', () => {
    const downloading = game({
        install_status: InstallStatus.Downloading,
        download_progress: {
            downloaded_bytes: 50,
            total_bytes: 100,
            bytes_per_second: 12_500_000,
            active_peer_count: 2,
        },
    });

    assertEquals(
        formatBytesPerSecond(12_500_000),
        '12.5 MB/s',
        'speed formatter should use compact decimal units',
    );
    assertEquals(
        actionLabel(downloading),
        'Downloading… 12.5 MB/s',
        'download label should include speed',
    );
});

Deno.test('downloading state is distinct and stays on the local filter', () => {
    const downloading = game({
        id: 'downloading',
        name: 'Downloading',
        install_status: InstallStatus.Downloading,
    });
    const local = game({
        id: 'local',
        name: 'Local',
        downloaded: true,
    });
    const remote = game({
        id: 'remote',
        name: 'Remote',
        peer_count: 1,
    });

    assertEquals(
        deriveState(downloading),
        'downloading',
        'download operation should render the dedicated downloading state',
    );
    assertEquals(
        countByFilter([downloading, local, remote]).local,
        2,
        'local filter count should include in-flight downloads',
    );
    assertEquals(
        applyFilterAndSort([downloading, local, remote], 'local', 'status', '').length,
        2,
        'local filter should include in-flight downloads',
    );
});

Deno.test('download progress formatting matches the progress-bar layouts', () => {
    const downloading = game({
        install_status: InstallStatus.Downloading,
        download_progress: {
            downloaded_bytes: 12 * 1024 * 1024 * 1024,
            total_bytes: 35 * 1024 * 1024 * 1024,
            bytes_per_second: 49_400_000,
            active_peer_count: 3,
        },
    });

    assertEquals(
        Math.round(downloadProgressPercent(downloading)),
        34,
        'progress percent should come from backend byte counters',
    );
    assertEquals(formatDownloadSpeed(49_400_000), '49.4 MB/s', 'large bar speed format');
    assertEquals(formatDownloadSpeedShort(49_400_000), '49 MB/s', 'card speed format');
    assertEquals(
        formatDownloadBytes(12 * 1024 * 1024 * 1024),
        '12 GB',
        'downloaded byte format should avoid noisy trailing decimals',
    );
    assertEquals(formatDownloadEta(485), '8 min', 'eta format should stay compact');
});