#include <QQmlEngine>
#include <QQuickWindow>
#include <QtTest>

#include "render/OffscreenQuickRenderer.h"
#include "render/RenderBackend.h"

// Renders a known scene through the real offscreen pipeline (backend +
// QQuickRenderControl) and checks the texture content via readback. The backend
// comes from VRDASH_TEST_API (opengl / vulkan): the graphics API is
// process-global, so CTest runs one process each.
class RenderTest : public QObject {
  Q_OBJECT
 private slots:
  void initTestCase() {
    GraphicsApi api = GraphicsApi::OpenGL;
    const QString apiName =
        qEnvironmentVariable("VRDASH_TEST_API", QStringLiteral("opengl"));
    QVERIFY2(parseGraphicsApi(apiName, &api), qPrintable(apiName));
    m_backend = createRenderBackend(api);
    if (!m_backend)
      QSKIP(qPrintable(apiName + QStringLiteral(" not compiled in")));
    QQuickWindow::setGraphicsApi(m_backend->graphicsApi());
    QString error;
    if (!m_backend->initialize({}, &error))
      QSKIP(qPrintable(
          QStringLiteral("No %1 context: %2").arg(m_backend->name(), error)));
  }

  void rendersSceneUpright() {
    QQmlEngine engine;
    const QSize size(64, 32);
    OffscreenQuickRenderer renderer(*m_backend, size);
    QString error;
    QVERIFY2(renderer.initialize(engine, "RenderTest", "TwoTone", &error),
             qPrintable(error));

    int sinkCalls = 0;
    vr::Texture_t submitted{};
    renderer.setFrameSink(
        [&](const vr::Texture_t& texture, const vr::VRTextureBounds_t&) {
          ++sinkCalls;
          submitted = texture;
        });
    renderer.renderNow();

    QCOMPARE(sinkCalls, 1);
    QVERIFY(submitted.handle != nullptr);
    const auto expectedType =
        m_backend->graphicsApi() == QSGRendererInterface::Vulkan
            ? vr::TextureType_Vulkan
            : vr::TextureType_OpenGL;
    QCOMPARE(submitted.eType, expectedType);
    if (submitted.eType == vr::TextureType_Vulkan) {
      const auto* vk =
          static_cast<const vr::VRVulkanTextureData_t*>(submitted.handle);
      QVERIFY(vk->m_nImage != 0 && vk->m_pDevice && vk->m_pQueue &&
              vk->m_pInstance);
      QCOMPARE(vk->m_nWidth, uint32_t(size.width()));
    }
    QVERIFY(!m_backend->deviceName().isEmpty());

    const QImage image = m_backend->readback();
    QCOMPARE(image.size(), size);
    QCOMPARE(image.pixelColor(size.width() / 2, 4), QColor(255, 0, 0));
    QCOMPARE(image.pixelColor(size.width() / 2, size.height() - 4),
             QColor(0, 0, 255));
  }

  // Several frames in a row exercise the per-frame state handling (e.g.
  // Vulkan layout transitions between Qt's frames and the SteamVR
  // hand-off).
  void rendersRepeatedly() {
    QQmlEngine engine;
    OffscreenQuickRenderer renderer(*m_backend, {32, 32});
    QString error;
    QVERIFY2(renderer.initialize(engine, "RenderTest", "TwoTone", &error),
             qPrintable(error));
    for (int i = 0; i < 5; ++i) renderer.renderNow();
    QCOMPARE(m_backend->readback().pixelColor(16, 2), QColor(255, 0, 0));
  }

  // An animated scene must render at the fps cap even when each frame
  // takes noticeable time: pacing is measured from frame start, not added
  // after the frame.
  void pacingHoldsFrameRateWithSlowFrames() {
    QQmlEngine engine;
    OffscreenQuickRenderer renderer(*m_backend, {32, 32});
    QString error;
    QVERIFY2(renderer.initialize(engine, "RenderTest", "Spinner", &error),
             qPrintable(error));
    int frames = 0;
    renderer.setFrameSink(
        [&](const vr::Texture_t&, const vr::VRTextureBounds_t&) {
          ++frames;
          QThread::usleep(3000);  // e.g. a slow SteamVR hand-off
        });
    renderer.setMaxFps(60);
    renderer.setActive(true);
    QTest::qWait(300);  // warm-up
    frames = 0;
    QElapsedTimer timer;
    timer.start();
    QTest::qWait(2000);
    const double fps = frames * 1000.0 / timer.elapsed();
    renderer.setActive(false);
    qInfo("measured %.1f fps", fps);
    QVERIFY2(fps > 57.0 && fps < 63.0, qPrintable(QString::number(fps)));
  }

  void cleanupTestCase() { m_backend.reset(); }

 private:
  std::unique_ptr<RenderBackend> m_backend;
};

QTEST_MAIN(RenderTest)
#include "tst_render.moc"