#include <psemek/ui/painter_impl.hpp>

#include <psemek/gfx/program.hpp>
#include <psemek/gfx/array.hpp>
#include <psemek/gfx/buffer.hpp>

namespace psemek::ui
{

	static char const colored_vs[] =
R"(#version 330

uniform mat4 u_transform;

layout (location = 0) in vec2 in_position;
layout (location = 1) in uint in_depth;
layout (location = 2) in vec4 in_color;

out vec4 color;

void main()
{
	gl_Position = u_transform * vec4(in_position, 1.0 - float(in_depth) / 16777216.0 * 2.0, 1.0);
	color = in_color;
}
)";

	static char const colored_fs[] =
R"(#version 330

in vec4 color;

out vec4 out_color;

void main()
{
	out_color = color;
}
)";

	struct colored_vertex
	{
		geom::point<float, 2> position;
		std::uint32_t depth;
		gfx::color_rgba color;
	};
	static_assert(sizeof(colored_vertex) == 16);

	struct painter_impl::impl
	{
		std::uint32_t depth = 0;

		gfx::program colored_program;
		gfx::array colored_vao;
		gfx::buffer colored_vbo;
		gfx::buffer colored_ebo;

		std::vector<colored_vertex> colored_vertices;
		std::vector<std::uint32_t> colored_indices;

		impl();
	};

	painter_impl::impl::impl()
		: colored_program{colored_vs, colored_fs}
	{
		colored_vao.bind();
		colored_vbo.bind();
		gl::EnableVertexAttribArray(0);
		gl::VertexAttribPointer(0, 2, gl::FLOAT, gl::FALSE, sizeof(colored_vertex), reinterpret_cast<void const *>(0));
		gl::EnableVertexAttribArray(1);
		gl::VertexAttribIPointer(1, 1, gl::UNSIGNED_INT, sizeof(colored_vertex), reinterpret_cast<void const *>(8));
		gl::EnableVertexAttribArray(2);
		gl::VertexAttribPointer(2, 4, gl::UNSIGNED_BYTE, gl::TRUE, sizeof(colored_vertex), reinterpret_cast<void const *>(12));
		gl::BindBuffer(gl::ELEMENT_ARRAY_BUFFER, colored_ebo.id());
	}

	painter_impl::painter_impl()
		: pimpl_{make_impl()}
	{}

	painter_impl::~painter_impl() = default;

	void painter_impl::draw_rect(geom::box<float, 2> const & rect, gfx::color_rgba const & color)
	{
		std::uint32_t const depth = impl().depth++;
		std::uint32_t const base = impl().colored_vertices.size();

		impl().colored_vertices.push_back({rect.corner(0.f, 0.f), depth, color});
		impl().colored_vertices.push_back({rect.corner(1.f, 0.f), depth, color});
		impl().colored_vertices.push_back({rect.corner(0.f, 1.f), depth, color});
		impl().colored_vertices.push_back({rect.corner(1.f, 1.f), depth, color});

		impl().colored_indices.insert(impl().colored_indices.end(), {base + 0, base + 1, base + 2, base + 2, base + 1, base + 3});
	}

	void painter_impl::render(geom::matrix<float, 4, 4> const & transform)
	{
		impl().colored_vbo.load(impl().colored_vertices);
		impl().colored_ebo.load(impl().colored_indices);

		int const colored_count = impl().colored_indices.size();

		impl().colored_vertices.clear();
		impl().colored_indices.clear();

		impl().depth = 0;

		impl().colored_program.bind();
		impl().colored_program["u_transform"] = transform;
		impl().colored_vao.bind();
		gl::DrawElements(gl::TRIANGLES, colored_count, gl::UNSIGNED_INT, nullptr);
	}

}