#include "device/dvc_buffer_accessor.h"
#include "math/dvc_vector2.h"
#include "math/dvc_vector3.h"
#include "math/dvc_matrix4.h"
#include "pipe/dvc_render_pipe.h"
#include "device/dvc_uniform_buffer.h"

template<bool WithNormal, bool WithUV>
StandardVertexShader<WithNormal, WithUV>::StandardVertexShader()
{
	m_outputVertexDesc.addElement("v_position", davinci::VET_POSITION, davinci::CT_Float32, davinci::DT_Vec3);

	if constexpr(WithNormal)
		m_outputVertexDesc.addElement("v_normal", davinci::VET_NORMAL, davinci::CT_Float32, davinci::DT_Vec3);

	if constexpr(WithUV)
		m_outputVertexDesc.addElement("v_uv", davinci::VET_TEXCOORD_0, davinci::CT_Float32, davinci::DT_Vec2);
}

template<bool WithNormal, bool WithUV>
StandardVertexShader<WithNormal, WithUV>::~StandardVertexShader()
{

}

template<std::size_t N>
struct CompileTimeString {
    std::array<char, N> data{};
    std::size_t size = 0;
    
    constexpr void append(const char* str, std::size_t len) {
        for (std::size_t i = 0; i < len; ++i) {
            data[size++] = str[i];
        }
    }
    
    constexpr void append(const char* str) {
        while (*str) {
            data[size++] = *str++;
        }
    }
    
    constexpr const char* c_str() const { return data.data(); }
    constexpr std::string_view view() const { return {data.data(), size}; }
};

template<bool WithNormal, bool WithUV>
constexpr auto buildNameString() 
{
	constexpr const char* prefix = "standard";
	constexpr const char* normalString = WithNormal ? "+normal" : "-normal";
	constexpr const char* uvString = WithUV ? "+uv" : "-uv";

	constexpr std::size_t total_len =  std::char_traits<char>::length(prefix) 
		+  std::char_traits<char>::length(normalString) 
		+  std::char_traits<char>::length(uvString);

	CompileTimeString<total_len> result;
    result.append(prefix);
    result.append(normalString);
    result.append(uvString);
    result.append(""); // null terminator
	return result;
}

template<bool WithNormal, bool WithUV>
const char* StandardVertexShader<WithNormal, WithUV>::getName(void) const
{
	static constexpr auto strName = buildNameString<WithNormal, WithUV>();
	const char* p = strName.c_str();
	return p;
}

template<bool WithNormal, bool WithUV>
const davinci::VertexDesc& StandardVertexShader<WithNormal, WithUV>::getOutputVertexDesc() const
{
	return m_outputVertexDesc;
}

template<bool WithNormal, bool WithUV>
size_t StandardVertexShader<WithNormal, WithUV>::getOutputVertexByteSize(void) const
{
	return m_outputVertexDesc.vertexByteSize();
}

template<bool WithNormal, bool WithUV>
void StandardVertexShader<WithNormal, WithUV>::prepare(const davinci::RenderPipe* pipe, SetInputAttributeFunc setInputAttributeFunc)
{
	m_pipe = pipe;

	std::get<iPOSITION()>(m_inputAccessors) = setInputAttributeFunc(davinci::VET_POSITION);

	if constexpr(WithNormal)	
		std::get<iNORMAL()>(m_inputAccessors) = setInputAttributeFunc(davinci::VET_NORMAL);

	if constexpr(WithUV)	
		std::get<iUV()>(m_inputAccessors) = setInputAttributeFunc(davinci::VET_TEXCOORD_0);
	
}
/*
template<bool WithNormal, bool WithUV>
davinci::DeviceBufferAccessorConstPtr& StandardVertexShader<WithNormal, WithUV>::getPositionAccessor()
{
	return std::get<0>(m_inputAccessors);
}

template<bool WithNormal, bool WithUV>
davinci::DeviceBufferAccessorConstPtr& StandardVertexShader<WithNormal, WithUV>::getNormalAccessor()
{
	if constexpr(WithNormal)
		return std::get<1>(m_inputAccessors);
	else
		return nullptr;
}

template<bool WithNormal, bool WithUV>
davinci::DeviceBufferAccessorConstPtr& StandardVertexShader<WithNormal, WithUV>::getUVAccessor()
{
	if constexpr(WithUV)
		return std::get<WithNormal+1>(m_inputAccessors);
	else
		return nullptr;
}
*/
template<bool WithNormal, bool WithUV>
void StandardVertexShader<WithNormal, WithUV>::process(size_t index, void* outputVertex, davinci::fVector3& vertexWorldPos)
{
	static const float DEFAULT_POSITION[] = {0.f, 0.f, 0.f};
	static const float32_t DEFAULT_NORMAL[] = { 0.f, 0.f, 0.f };
	static const float32_t DEFAULT_TEXCOORD0[] = { 0.f, 0.f};

	const davinci::UniformBuffer& uniformBuffer = m_pipe->getUniformBuffer();
	
	davinci::DeviceBufferAccessorConstPtr inputPosition = std::get<0>(m_inputAccessors);

	davinci::DeviceBufferAccessorConstPtr inputNormal = nullptr;
	if constexpr(WithNormal)	
		inputNormal = std::get<iNORMAL()>(m_inputAccessors);

	davinci::DeviceBufferAccessorConstPtr inputUV = nullptr;
	if constexpr(WithUV)	
		inputUV = std::get<iUV()>(m_inputAccessors);

	davinci::fVector3 a_position(inputPosition ? (const float32_t*)(inputPosition->getElement(index)) : DEFAULT_POSITION);
	davinci::fVector3 a_normal(inputNormal ? (const float32_t*)(inputNormal->getElement(index)) : DEFAULT_NORMAL);
	davinci::fVector2 a_uv(inputUV ? (const float32_t*)(inputUV->getElement(index)) : DEFAULT_TEXCOORD0);

	davinci::fMatrix4 mat_world = davinci::fMatrix4::IDENTITY;
	if (davinci::fMatrix4* p_mat_world = (davinci::fMatrix4*)(uniformBuffer.getAttribute("self:world_transform")))
	{
		mat_world = *p_mat_world;
	}

	davinci::fMatrix4 mat_camera_view_proj = davinci::fMatrix4::IDENTITY;
	if (davinci::fMatrix4* p_mat_camera_view_proj = (davinci::fMatrix4*)(uniformBuffer.getAttribute("camera:view_proj_mat")))
	{
		mat_camera_view_proj = *p_mat_camera_view_proj;
	}

	vertexWorldPos = mat_world * a_position;
	davinci::fVector3 v_position = mat_camera_view_proj * vertexWorldPos;

	int32_t outputOffset=0;
	memcpy((char*)outputVertex + m_outputVertexDesc.getElement(outputOffset++)->offset, &v_position, sizeof(davinci::fVector3));
	
	if constexpr(WithNormal)	
	{
		davinci::fMatrix4 matNormal = davinci::fMatrix4::IDENTITY;
		if (davinci::fMatrix4* p_mat_normal = (davinci::fMatrix4*)(uniformBuffer.getAttribute("self:world_transform_inverse_trans")))
		{
			matNormal = *p_mat_normal;
		}
		davinci::fVector3 v_normal = (matNormal * davinci::fVector4(a_normal, 0)).xyz().normalise();
		memcpy((char*)outputVertex + m_outputVertexDesc.getElement(outputOffset++)->offset, &v_normal, sizeof(davinci::fVector3));
	}

	if constexpr(WithUV)	
	{
		memcpy((char*)outputVertex + m_outputVertexDesc.getElement(outputOffset++)->offset, &a_uv, sizeof(float32_t) * 2);
	}
}