// Render test for the render backends (src/render/), adapted from the
// vrdashboard template's tst_render. It drives a backend and
// QQuickRenderControl in the same order as OverlayController::SetWidget() and
// renderOverlay(), then checks the texture handed to SteamVR and its content
// (via readback).
//
// The backend comes from OVRAS_TEST_API (opengl / vulkan): the graphics API is
// process-wide, so CTest runs one process per API. Without a GPU context the
// test skips itself. With OVRAS_VULKAN_VALIDATION=1 the Vulkan validation
// layers are enabled (build_scripts/steamframe/container-test.sh).

#include <QQmlComponent>
#include <QQmlEngine>
#include <QQuickItem>
#include <QQuickRenderControl>
#include <QQuickWindow>
#include <QtTest>
#include <memory>

#include "render/RenderBackend.h"

class RenderTest : public QObject
{
    Q_OBJECT

private slots:
    void initTestCase()
    {
        GraphicsApi api = GraphicsApi::OpenGL;
        const QString apiName
            = qEnvironmentVariable( "OVRAS_TEST_API", "opengl" );
        QVERIFY2( parseGraphicsApi( apiName, &api ), qPrintable( apiName ) );
        m_backend = createRenderBackend( api );
        if ( !m_backend )
        {
            QSKIP( qPrintable( apiName + " not compiled in" ) );
        }
        // Before any QQuickWindow exists, as in main().
        QQuickWindow::setGraphicsApi( m_backend->graphicsApi() );
        QString error;
        // No SteamVR here: empty interop, the backend picks defaults.
        if ( !m_backend->initialize( {}, &error ) )
        {
            QSKIP( qPrintable( QString( "No %1 context: %2" )
                                   .arg( m_backend->name(), error ) ) );
        }
    }

    // One frame of a known scene (top red, bottom blue): texture type and
    // description for SteamVR, content and orientation.
    void rendersSceneUpright()
    {
        const QSize size( 64, 32 );
        Scene scene( *m_backend, size );
        QVERIFY2( scene.error.isEmpty(), qPrintable( scene.error ) );

        const vr::Texture_t texture = scene.renderFrame();
        QVERIFY( texture.handle != nullptr );
        const auto expectedType
            = m_backend->graphicsApi() == QSGRendererInterface::Vulkan
                  ? vr::TextureType_Vulkan
                  : vr::TextureType_OpenGL;
        QCOMPARE( texture.eType, expectedType );
        if ( texture.eType == vr::TextureType_Vulkan )
        {
            const auto* vk = static_cast<const vr::VRVulkanTextureData_t*>(
                texture.handle );
            QVERIFY( vk->m_nImage != 0 && vk->m_pDevice && vk->m_pQueue
                     && vk->m_pInstance );
            QCOMPARE( vk->m_nWidth, static_cast<uint32_t>( size.width() ) );
            // VK_FORMAT_R8G8B8A8_UNORM, the format SteamVR gets told.
            QCOMPARE( vk->m_nFormat, 37u );
        }
        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.
    // the Vulkan layout transitions between Qt's frames and the SteamVR
    // hand-off).
    void rendersRepeatedly()
    {
        Scene scene( *m_backend, { 32, 32 } );
        QVERIFY2( scene.error.isEmpty(), qPrintable( scene.error ) );
        for ( int i = 0; i < 5; ++i )
        {
            scene.renderFrame();
        }
        QCOMPARE( m_backend->readback().pixelColor( 16, 2 ),
                  QColor( 255, 0, 0 ) );
    }

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

private:
    // The TwoTone scene in an offscreen window, set up like
    // OverlayController::SetWidget(). Tears down like
    // OverlayController::Shutdown() (minus VR_Shutdown).
    struct Scene
    {
        Scene( RenderBackend& backend, QSize size ) : backend( backend )
        {
            window = std::make_unique<QQuickWindow>( &renderControl );
            window->setGeometry( 0, 0, size.width(), size.height() );
            QQmlComponent component( &engine );
            component.loadFromModule( "RenderTest", "TwoTone" );
            root.reset( qobject_cast<QQuickItem*>( component.create() ) );
            if ( !root )
            {
                error = component.errorString();
                return;
            }
            root->setSize( size );
            root->setParentItem( window->contentItem() );

            backend.configureWindow( window.get() );
            if ( !backend.makeCurrent() || !renderControl.initialize() )
            {
                error = "QQuickRenderControl::initialize failed";
                return;
            }
            if ( !backend.attachWindow( window.get(), &error ) )
            {
                return;
            }
            const QQuickRenderTarget target
                = backend.createRenderTarget( size );
            if ( target.isNull() )
            {
                error = "createRenderTarget failed";
                return;
            }
            window->setRenderTarget( target );
        }

        ~Scene()
        {
            backend.makeCurrent();
            root.reset();
            backend.releaseRenderTarget();
            backend.detachWindow();
            window.reset();
        }

        // One frame as in OverlayController::renderOverlay(); returns what
        // would be handed to IVROverlay::SetOverlayTexture.
        vr::Texture_t renderFrame()
        {
            backend.makeCurrent();
            backend.beginFrame();
            renderControl.polishItems();
            renderControl.beginFrame();
            renderControl.sync();
            renderControl.render();
            renderControl.endFrame();
            backend.finishFrame();
            return backend.vrTexture();
        }

        RenderBackend& backend;
        QQmlEngine engine;
        // Destroyed after the window (declared before it): the window
        // belongs to this render control.
        QQuickRenderControl renderControl;
        std::unique_ptr<QQuickWindow> window;
        std::unique_ptr<QQuickItem> root;
        QString error;
    };

    std::unique_ptr<RenderBackend> m_backend;
};

QTEST_MAIN( RenderTest )
#include "tst_render.moc"