// 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
//
#pragma once

#include "ui/gl/gl_math.h"

#include <QtGui/QOpenGLFunctions>

namespace Ui::GL {
namespace details {

void GenerateTextures(
	QOpenGLFunctions &f,
	gsl::span<GLuint> values,
	GLint filter,
	GLint clamp);
void DestroyTextures(QOpenGLFunctions *f, gsl::span<GLuint> values);

void GenerateFramebuffers(QOpenGLFunctions &f, gsl::span<GLuint> values);
void DestroyFramebuffers(QOpenGLFunctions *f, gsl::span<GLuint> values);

} // namespace details

template <size_t Count>
class Textures final {
public:
	static_assert(Count > 0);

	void ensureCreated(
			QOpenGLFunctions &f,
			GLint filter = GL_LINEAR,
			GLint clamp = GL_CLAMP_TO_EDGE) {
		if (!created()) {
			details::GenerateTextures(
				f,
				gsl::make_span(_values),
				filter,
				clamp);
		}
	}
	void destroy(QOpenGLFunctions *f) {
		if (created()) {
			details::DestroyTextures(f, gsl::make_span(_values));
		}
	}

	void bind(QOpenGLFunctions &f, int index) const {
		Expects(index >= 0 && index < Count);

		f.glBindTexture(GL_TEXTURE_2D, _values[index]);
	}

	[[nodiscard]] GLuint id(int index) const {
		Expects(index >= 0 && index < Count);

		return _values[index];
	}

	[[nodiscard]] bool created() const {
		return (_values[0] != 0);
	}

private:
	std::array<GLuint, Count> _values = { { 0 } };

};

template <size_t Count>
class Framebuffers final {
public:
	static_assert(Count > 0);

	void ensureCreated(QOpenGLFunctions &f) {
		if (!created()) {
			details::GenerateFramebuffers(f, gsl::make_span(_values));
		}
	}
	void destroy(QOpenGLFunctions *f) {
		if (created()) {
			details::DestroyFramebuffers(f, gsl::make_span(_values));
		}
	}

	void bind(QOpenGLFunctions &f, int index) const {
		Expects(index >= 0 && index < Count);

		f.glBindFramebuffer(GL_FRAMEBUFFER, _values[index]);
	}

	[[nodiscard]] bool created() const {
		return (_values[0] != 0);
	}

private:
	std::array<GLuint, Count> _values = { { 0 } };

};

struct TexturedRect {
	Rect geometry;
	Rect texture;
};

class Image final {
public:
	void setImage(QImage image, QSize subimage = QSize());
	[[nodiscard]] const QImage &image() const;
	[[nodiscard]] QImage takeImage();
	void invalidate();

	void bind(QOpenGLFunctions &f);
	void destroy(QOpenGLFunctions *f);

	[[nodiscard]] TexturedRect texturedRect(
		const QRect &geometry,
		const QRect &texture,
		const QRect &clip = QRect());

	explicit operator bool() const {
		return !_image.isNull();
	}

private:
	QImage _image;
	QImage _storage;
	Textures<1> _textures;
	qint64 _cacheKey = 0;
	QSize _subimage;
	QSize _textureSize;

};

#ifdef Q_OS_WIN
inline constexpr auto kFormatRGBA = GL_BGRA_EXT;
inline constexpr auto kSwizzleRedBlue = false;
#else // Q_OS_WIN
inline constexpr auto kFormatRGBA = GL_RGBA;
inline constexpr auto kSwizzleRedBlue = true;
#endif // Q_OS_WIN

} // namespace Ui::GL