// This file is part of Desktop App Toolkit,
// a set of libraries for developing nice desktop applications.
//
// For license and copyright information please follow this link:
// https://github.com/desktop-app/legal/blob/master/LEGAL
//
#include "ui/gl/gl_surface.h"

#include "ui/rp_widget.h"
#include "ui/painter.h"

#include <QtGui/QtEvents>
#include <QtGui/QOpenGLContext>
#include <QtGui/QWindow>
#include <QtGui/QPaintEngine>
#include <QtWidgets/QOpenGLWidget>

namespace Ui::GL {
namespace {

struct SurfaceTraits : RpWidgetDefaultTraits {
	static constexpr bool kSetZeroGeometry = false;
};

class SurfaceOpenGL final
	: public RpWidgetBase<QOpenGLWidget, SurfaceTraits> {
public:
	SurfaceOpenGL(QWidget *parent, std::unique_ptr<Renderer> renderer);
	~SurfaceOpenGL();

private:
	void initializeGL() override;
	void resizeGL(int w, int h) override;
	void paintEvent(QPaintEvent *e) override;
	void callDeInit();

	const std::unique_ptr<Renderer> _renderer;
	QMetaObject::Connection _connection;

};

class SurfaceRaster final : public RpWidgetBase<QWidget, SurfaceTraits> {
public:
	SurfaceRaster(QWidget *parent, std::unique_ptr<Renderer> renderer);

private:
	void paintEvent(QPaintEvent *e) override;

	const std::unique_ptr<Renderer> _renderer;

};

SurfaceOpenGL::SurfaceOpenGL(
	QWidget *parent,
	std::unique_ptr<Renderer> renderer)
: RpWidgetBase<QOpenGLWidget, SurfaceTraits>(parent)
, _renderer(std::move(renderer)) {
}

SurfaceOpenGL::~SurfaceOpenGL() {
	callDeInit();
}

void SurfaceOpenGL::initializeGL() {
	Expects(window()->windowHandle() != nullptr);

	if (_connection) {
		QObject::disconnect(base::take(_connection));
	}
	const auto context = this->context();
	_connection = QObject::connect(
		context,
		&QOpenGLContext::aboutToBeDestroyed,
		[=] { callDeInit(); });
	_renderer->init(this, *context->functions());
}

void SurfaceOpenGL::resizeGL(int w, int h) {
	_renderer->resize(this, *context()->functions(), w, h);
}

void SurfaceOpenGL::paintEvent(QPaintEvent *e) {
	if (!updatesEnabled() || size().isEmpty() || !isValid()) {
		return;
	}
	auto redirectOffset = QPoint();
	const auto rpd = redirected(&redirectOffset);
	const auto device = rpd ? rpd : static_cast<QPaintDevice*>(this);
	const auto engine = device->paintEngine();
	if (!engine) {
		return;
	}
	engine->begin(device);
	const auto f = context()->functions();
	if (const auto bg = _renderer->clearColor()) {
		f->glClearColor(bg->redF(), bg->greenF(), bg->blueF(), bg->alphaF());
		f->glClear(GL_COLOR_BUFFER_BIT);
	}
	f->glDisable(GL_BLEND);
	f->glViewport(0, 0, device->width(), device->height());
	_renderer->paint(this, *f);
	engine->end();
}

void SurfaceOpenGL::callDeInit() {
	if (!_connection) {
		return;
	}
	QObject::disconnect(base::take(_connection));
	const auto surface = window()->windowHandle();
	Assert(surface != nullptr);
	const auto context = this->context();
	context->makeCurrent(surface);
	_renderer->deinit(this, *context->functions());
}

SurfaceRaster::SurfaceRaster(
	QWidget *parent,
	std::unique_ptr<Renderer> renderer)
: RpWidgetBase<QWidget, SurfaceTraits>(parent)
, _renderer(std::move(renderer)) {
}

void SurfaceRaster::paintEvent(QPaintEvent *e) {
	_renderer->paintFallback(Painter(this), e->region(), Backend::Raster);
}

} // namespace

void Renderer::paint(
		not_null<QOpenGLWidget*> widget,
		QOpenGLFunctions &f) {
	paintFallback(Painter(widget.get()), widget->rect(), Backend::OpenGL);
}

std::unique_ptr<RpWidgetWrap> CreateSurface(
		Fn<ChosenRenderer(Capabilities)> chooseRenderer) {
	auto chosen = chooseRenderer(CheckCapabilities(nullptr));
	switch (chosen.backend) {
	case Backend::OpenGL:
		return std::make_unique<SurfaceOpenGL>(
			nullptr,
			std::move(chosen.renderer));
	case Backend::Raster:
		return std::make_unique<SurfaceRaster>(
			nullptr,
			std::move(chosen.renderer));
	}
	Unexpected("Backend value in Ui::GL::CreateSurface.");
}

std::unique_ptr<RpWidgetWrap> CreateSurface(
		QWidget *parent,
		ChosenRenderer chosen) {
	switch (chosen.backend) {
	case Backend::OpenGL:
		return std::make_unique<SurfaceOpenGL>(
			parent,
			std::move(chosen.renderer));
	case Backend::Raster:
		return std::make_unique<SurfaceRaster>(
			parent,
			std::move(chosen.renderer));
	}
	Unexpected("Backend value in Ui::GL::CreateSurface.");
}

} // namespace Ui::GL