/********************************************************************
 KWin - the KDE window manager
 This file is part of the KDE project.

Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*********************************************************************/
#include "egl_gbm_backend.h"
// kwin
#include "composite.h"
#include "drm_backend.h"
#include "drm_output.h"
#include "logging.h"
#include "options.h"
#include "screens.h"
// kwin libs
#include <kwinglplatform.h>
// Qt
#include <QOpenGLContext>
// system
#include <gbm.h>

namespace KWin
{

EglGbmBackend::EglGbmBackend(DrmBackend *b)
    : QObject(NULL)
    , AbstractEglBackend()
    , m_backend(b)
{
    // Egl is always direct rendering
    setIsDirectRendering(true);
    setSyncsToVBlank(true);
    connect(m_backend, &DrmBackend::outputAdded, this, &EglGbmBackend::createOutput);
    connect(m_backend, &DrmBackend::outputRemoved, this,
        [this] (DrmOutput *output) {
            auto it = std::find_if(m_outputs.begin(), m_outputs.end(),
                [output] (const Output &o) {
                    return o.output == output;
                }
            );
            if (it == m_outputs.end()) {
                return;
            }
            cleanupOutput(*it);
            m_outputs.erase(it);
        }
    );
}

EglGbmBackend::~EglGbmBackend()
{
    // TODO: cleanup front buffer?
    cleanup();
}

void EglGbmBackend::cleanupSurfaces()
{
    for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {
        cleanupOutput(*it);
    }
}

void EglGbmBackend::cleanupOutput(const Output &o)
{
    // TODO: cleanup front buffer?
    if (o.eglSurface != EGL_NO_SURFACE) {
        eglDestroySurface(eglDisplay(), o.eglSurface);
    }
    if (o.gbmSurface) {
        gbm_surface_destroy(o.gbmSurface);
    }
}

bool EglGbmBackend::initializeEgl()
{
    initClientExtensions();
    EGLDisplay display = m_backend->sceneEglDisplay();

    // Use eglGetPlatformDisplayEXT() to get the display pointer
    // if the implementation supports it.
    if (display == EGL_NO_DISPLAY) {
        if (!hasClientExtension(QByteArrayLiteral("EGL_EXT_platform_base")) ||
                !hasClientExtension(QByteArrayLiteral("EGL_MESA_platform_gbm"))) {
            setFailed("EGL_EXT_platform_base and/or EGL_MESA_platform_gbm missing");
            return false;
        }

        auto device = gbm_create_device(m_backend->fd());
        if (!device) {
            setFailed("Could not create gbm device");
            return false;
        }
        m_backend->setGbmDevice(device);

        display = eglGetPlatformDisplayEXT(EGL_PLATFORM_GBM_MESA, device, nullptr);
    }

    if (display == EGL_NO_DISPLAY)
        return false;
    setEglDisplay(display);
    return initEglAPI();
}

void EglGbmBackend::init()
{
    if (!initializeEgl()) {
        setFailed("Could not initialize egl");
        return;
    }
    if (!initRenderingContext()) {
        setFailed("Could not initialize rendering context");
        return;
    }

    initKWinGL();
    initBufferAge();
    initWayland();
}

bool EglGbmBackend::initRenderingContext()
{
    initBufferConfigs();

    if (!createContext()) {
        return false;
    }

    const auto outputs = m_backend->outputs();
    for (DrmOutput *drmOutput: outputs) {
        createOutput(drmOutput);
    }
    if (m_outputs.isEmpty()) {
        qCCritical(KWIN_DRM) << "Create Window Surfaces failed";
        return false;
    }
    // set our first surface as the one for the abstract backend, just to make it happy
    setSurface(m_outputs.first().eglSurface);

    return makeContextCurrent(m_outputs.first());
}

void EglGbmBackend::createOutput(DrmOutput *drmOutput)
{
    Output o;
    o.output = drmOutput;
    o.gbmSurface = gbm_surface_create(m_backend->gbmDevice(), drmOutput->size().width(), drmOutput->size().height(),
                                        GBM_FORMAT_XRGB8888, GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING);
    if (!o.gbmSurface) {
        qCCritical(KWIN_DRM) << "Create gbm surface failed";
        return;
    }
    o.eglSurface = eglCreatePlatformWindowSurfaceEXT(eglDisplay(), config(), (void *)o.gbmSurface, nullptr);
    if (o.eglSurface == EGL_NO_SURFACE) {
        qCCritical(KWIN_DRM) << "Create Window Surface failed";
        gbm_surface_destroy(o.gbmSurface);
        return;
    }
    m_outputs << o;
}

bool EglGbmBackend::makeContextCurrent(const Output &output)
{
    const EGLSurface surface = output.eglSurface;
    if (surface == EGL_NO_SURFACE) {
        return false;
    }
    if (eglMakeCurrent(eglDisplay(), surface, surface, context()) == EGL_FALSE) {
        qCCritical(KWIN_DRM) << "Make Context Current failed";
        return false;
    }

    EGLint error = eglGetError();
    if (error != EGL_SUCCESS) {
        qCWarning(KWIN_DRM) << "Error occurred while creating context " << error;
        return false;
    }
    // TODO: ensure the viewport is set correctly each time
    const QSize &overall = screens()->size();
    const QRect &v = output.output->geometry();
    // TODO: are the values correct?
    glViewport(-v.x(), v.height() - overall.height() - v.y(), overall.width(), overall.height());
    return true;
}

bool EglGbmBackend::initBufferConfigs()
{
    const EGLint config_attribs[] = {
        EGL_SURFACE_TYPE,         EGL_WINDOW_BIT,
        EGL_RED_SIZE,             1,
        EGL_GREEN_SIZE,           1,
        EGL_BLUE_SIZE,            1,
        EGL_ALPHA_SIZE,           0,
        EGL_RENDERABLE_TYPE,      isOpenGLES() ? EGL_OPENGL_ES2_BIT : EGL_OPENGL_BIT,
        EGL_CONFIG_CAVEAT,        EGL_NONE,
        EGL_NONE,
    };

    EGLint count;
    EGLConfig configs[1024];
    if (eglChooseConfig(eglDisplay(), config_attribs, configs, 1, &count) == EGL_FALSE) {
        qCCritical(KWIN_DRM) << "choose config failed";
        return false;
    }
    if (count != 1) {
        qCCritical(KWIN_DRM) << "choose config did not return a config" << count;
        return false;
    }
    setConfig(configs[0]);

    return true;
}

void EglGbmBackend::present()
{
    for (auto &o: m_outputs) {
        makeContextCurrent(o);
        presentOnOutput(o);
    }
}

void EglGbmBackend::presentOnOutput(EglGbmBackend::Output &o)
{
    eglSwapBuffers(eglDisplay(), o.eglSurface);
    o.buffer = m_backend->createBuffer(o.gbmSurface);
    m_backend->present(o.buffer, o.output);
    if (supportsBufferAge()) {
        eglQuerySurface(eglDisplay(), o.eglSurface, EGL_BUFFER_AGE_EXT, &o.bufferAge);
    }

}

void EglGbmBackend::screenGeometryChanged(const QSize &size)
{
    Q_UNUSED(size)
    // TODO, create new buffer?
}

SceneOpenGL::TexturePrivate *EglGbmBackend::createBackendTexture(SceneOpenGL::Texture *texture)
{
    return new EglGbmTexture(texture, this);
}

QRegion EglGbmBackend::prepareRenderingFrame()
{
    startRenderTimer();
    return QRegion();
}

QRegion EglGbmBackend::prepareRenderingForScreen(int screenId)
{
    const Output &o = m_outputs.at(screenId);
    makeContextCurrent(o);
    if (supportsBufferAge()) {
        QRegion region;

        // Note: An age of zero means the buffer contents are undefined
        if (o.bufferAge > 0 && o.bufferAge <= o.damageHistory.count()) {
            for (int i = 0; i < o.bufferAge - 1; i++)
                region |= o.damageHistory[i];
        } else {
            region = o.output->geometry();
        }

        return region;
    }
    return QRegion();
}

void EglGbmBackend::endRenderingFrame(const QRegion &renderedRegion, const QRegion &damagedRegion)
{
    Q_UNUSED(renderedRegion)
    Q_UNUSED(damagedRegion)
}

void EglGbmBackend::endRenderingFrameForScreen(int screenId, const QRegion &renderedRegion, const QRegion &damagedRegion)
{
    Output &o = m_outputs[screenId];
    if (damagedRegion.intersected(o.output->geometry()).isEmpty() && screenId == 0) {

        // If the damaged region of a window is fully occluded, the only
        // rendering done, if any, will have been to repair a reused back
        // buffer, making it identical to the front buffer.
        //
        // In this case we won't post the back buffer. Instead we'll just
        // set the buffer age to 1, so the repaired regions won't be
        // rendered again in the next frame.
        if (!renderedRegion.intersected(o.output->geometry()).isEmpty())
            glFlush();

        for (auto &o: m_outputs) {
            o.bufferAge = 1;
        }
        return;
    }
    presentOnOutput(o);

    // Save the damaged region to history
    // Note: damage history is only collected for the first screen. For any other screen full repaints
    // are triggered. This is due to a limitation in Scene::paintGenericScreen which resets the Toplevel's
    // repaint. So multiple calls to Scene::paintScreen as it's done in multi-output rendering only
    // have correct damage information for the first screen. If we try to track damage nevertheless,
    // it creates artifacts. So for the time being we work around the problem by only supporting buffer
    // age on the first output. To properly support buffer age on all outputs the rendering needs to
    // be refactored in general.
    if (supportsBufferAge() && screenId == 0) {
        if (o.damageHistory.count() > 10) {
            o.damageHistory.removeLast();
        }

        o.damageHistory.prepend(damagedRegion.intersected(o.output->geometry()));
    }
}

bool EglGbmBackend::usesOverlayWindow() const
{
    return false;
}

bool EglGbmBackend::perScreenRendering() const
{
    return true;
}

/************************************************
 * EglTexture
 ************************************************/

EglGbmTexture::EglGbmTexture(KWin::SceneOpenGL::Texture *texture, EglGbmBackend *backend)
    : AbstractEglTexture(texture, backend)
{
}

EglGbmTexture::~EglGbmTexture() = default;

} // namespace
