/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code 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 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code 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 Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef ANTKEEPER_GL_VERTEX_BUFFER_HPP
#define ANTKEEPER_GL_VERTEX_BUFFER_HPP

#include <engine/gl/buffer-usage.hpp>
#include <cstddef>
#include <span>

namespace gl {

/**
 * Vertex buffer object (VBO).
 */
class vertex_buffer
{
public:
	/**
	 * Constructs a vertex buffer.
	 *
	 * @param usage Buffer usage hint.
	 * @param size Buffer size, in bytes.
	 * @param data Buffer data. If empty, buffer data will not be set.
	 *
	 * @except std::out_of_range Vertex buffer construct operation exceeded data bounds.
	 */
	/// @{
	vertex_buffer(buffer_usage usage, std::size_t size, std::span<const std::byte> data = {});
	
	inline explicit vertex_buffer(buffer_usage usage, std::span<const std::byte> data = {}):
		vertex_buffer(usage, data.size(), data)
	{}
	
	inline vertex_buffer():
		vertex_buffer(buffer_usage::static_draw, 0)
	{}
	/// @}
	
	/**
	 * Constructs a copy of a vertex buffer.
	 *
	 * @param buffer Buffer to copy.
	 */
	vertex_buffer(const vertex_buffer& buffer);
	
	/**
	 * Move-constructs a vertex buffer.
	 *
	 * @param buffer Buffer to move.
	 */
	vertex_buffer(vertex_buffer&& buffer);
	
	/// Destroys a vertex buffer.
	~vertex_buffer();
	
	/**
	 * Copies another vertex buffer.
	 *
	 * @param buffer Buffer to copy.
	 *
	 * @return Reference to this vertex buffer.
	 */
	vertex_buffer& operator=(const vertex_buffer& buffer);
	
	/**
	 * Moves another vertex buffer into this buffer.
	 *
	 * @param buffer Buffer to move.
	 *
	 * @return Reference to this vertex buffer.
	 */
	vertex_buffer& operator=(vertex_buffer&& buffer);
	
	/**
	 * Repurposes the vertex buffer, changing its usage hint, size, and updating its data.
	 *
	 * @param usage New buffer usage hint.
	 * @param size New buffer size, in bytes.
	 * @param data New buffer data. If empty, buffer data will not be updated.
	 *
	 * @except std::out_of_range Vertex buffer resize operation exceeded data bounds.
	 */
	/// @{
	void repurpose(buffer_usage usage, std::size_t size, std::span<const std::byte> data = {});
	
	inline void repurpose(buffer_usage usage, std::span<const std::byte> data)
	{
		repurpose(usage, data.size(), data);
	}
	
	inline void repurpose(buffer_usage usage)
	{
		repurpose(usage, m_size, {});
	}
	/// @}
	
	/**
	 * Resizes the vertex buffer.
	 *
	 * @param size New buffer size, in bytes.
	 * @param data New buffer data. If empty, buffer data will not be updated.
	 *
	 * @except std::out_of_range Vertex buffer resize operation exceeded data bounds.
	 */
	/// @{
	inline void resize(std::size_t size, std::span<const std::byte> data = {})
	{
		repurpose(m_usage, size, data);
	}
	
	inline void resize(std::span<const std::byte> data)
	{
		repurpose(m_usage, data.size(), data);
	}
	/// @}
	
	/**
	 * Writes data into the vertex buffer.
	 *
	 * @param offset Offset into the buffer's data, in bytes, where writing will begin.
	 * @param data Data to write into the buffer.
	 *
	 * @except std::out_of_range Vertex buffer write operation exceeded buffer bounds.
	 */
	/// @{
	void write(std::size_t offset, std::span<const std::byte> data);
	
	inline void write(std::span<const std::byte> data)
	{
		write(0, data);
	}
	/// @}
	
	/**
	 * Reads a subset of the buffer's data from the GL and returns it to the application.
	 *
	 * @param offset Offset into the buffer's data, in bytes, where reading will begin.
	 * @param data Data buffer where the read bytes will be stored.
	 *
	 * @except std::out_of_range Vertex buffer read operation exceeded buffer bounds.
	 */
	/// @{
	void read(std::size_t offset, std::span<std::byte> data) const;
	
	inline void read(std::span<std::byte> data) const
	{
		read(0, data);
	}
	/// @}
	
	/**
	 * Copies a subset of another vertex buffer's data into this vertex buffer.
	 *
	 * @param read_buffer Buffer from which data will be read.
	 * @param copy_size Number of bytes to copy from the read buffer into this buffer.
	 * @param read_offset Offset into the read buffer's data, in bytes, where reading will begin.
	 * @param write_offset Offset into the this buffer's data, in bytes, where writing will begin.
	 *
	 * @except std::out_of_range Vertex buffer copy operation exceeded read buffer bounds.
	 * @except std::out_of_range Vertex buffer copy operation exceeded write buffer bounds.
	 */
	void copy(const vertex_buffer& read_buffer, std::size_t copy_size, std::size_t read_offset = 0, std::size_t write_offset = 0);
	
	/// Returns the size of the buffer's data, in bytes.
	[[nodiscard]] inline constexpr std::size_t size() const noexcept
	{
		return m_size;
	}
	
	/// Return's the buffer's usage hint.
	[[nodiscard]] inline constexpr buffer_usage usage() const noexcept
	{
		return m_usage;
	}

private:
	friend class pipeline;
	
	unsigned int m_gl_named_buffer{0};
	buffer_usage m_usage{buffer_usage::static_draw};
	std::size_t m_size{0};
};

} // namespace gl

#endif // ANTKEEPER_GL_VERTEX_BUFFER_HPP