#include "VertexInputStateBuilder.h"
#include <stdexcept>
#include <cassert>

VertexInputStateBuilder& VertexInputStateBuilder::AddAttribute(Uint32 location, SDL_GPUVertexElementFormat type)
{
    Uint32 offset = 0;
    for (auto e : elements) {
        const Uint32 floatSize = sizeof(float);
        switch (e.format) {
        case SDL_GPU_VERTEXELEMENTFORMAT_FLOAT:
            offset += floatSize;
            break;
        case SDL_GPU_VERTEXELEMENTFORMAT_FLOAT2:
            offset += floatSize * 2;
            break;
        case SDL_GPU_VERTEXELEMENTFORMAT_FLOAT3:
            offset += floatSize * 3;
            break;
        case SDL_GPU_VERTEXELEMENTFORMAT_FLOAT4:
            offset += floatSize * 4;
            break;
        default:
            throw std::runtime_error("Unknown vertex element format");
            break;
        }
    }
    SDL_GPUVertexAttribute element = {};
    element.format = type;
    element.location = location;
    element.offset = offset;
    element.buffer_slot = 0;
    elements.push_back(element);
    return *this;
}

VertexInputStateBuilder& VertexInputStateBuilder::Instanced()
{
    isInstanced = true;
    return *this;
}

VertexInputStateBuilder& VertexInputStateBuilder::BuildDeferred()
{
    Build();
    return *this;
}

SDL_GPUVertexInputState VertexInputStateBuilder::Build()
{
    assert(elements.size());
    Uint32 pitch = 0;
    for (auto e : elements) {
        //pitch += e.format == SDL_GPU_VERTEXELEMENTFORMAT_FLOAT ? 4 : 16;
        const Uint32 floatSize = sizeof(float);
        switch (e.format) {
        case SDL_GPU_VERTEXELEMENTFORMAT_FLOAT:
            pitch += floatSize;
            break;
        case SDL_GPU_VERTEXELEMENTFORMAT_FLOAT2:
            pitch += floatSize * 2;
            break;
        case SDL_GPU_VERTEXELEMENTFORMAT_FLOAT3:
            pitch += floatSize * 3;
            break;
        case SDL_GPU_VERTEXELEMENTFORMAT_FLOAT4:
            pitch += floatSize * 4;
            break;
        default:
            throw std::runtime_error("Unknown vertex element format");
            break;
        }
    }
    description = {};
    description.slot = 0;
    description.pitch = pitch;
    description.input_rate = isInstanced ? SDL_GPU_VERTEXINPUTRATE_INSTANCE : SDL_GPU_VERTEXINPUTRATE_VERTEX;
    description.instance_step_rate = 0;

    state = {};
    state.vertex_buffer_descriptions = &description;
    state.num_vertex_buffers = 1;
    state.vertex_attributes = elements.data();
    state.num_vertex_attributes = elements.size();
    return state; // description is on stack and therefore this shit doesn't work becuase it gets overwritten later ughhhhhhh
}

SDL_GPUVertexInputState VertexInputStateBuilder::Use()
{
    return state;
}

VertexInputStateBuilder::VertexInputStateBuilder()
{
}

VertexInputStateBuilder::VertexInputStateBuilder(const VertexInputStateBuilder& other)
    : elements(other.elements),
    description(other.description),
    state(other.state)
{
    // Fix up the pointer — description was copied to a new address
    state.vertex_buffer_descriptions = &description;
    state.vertex_attributes = elements.data();
}

VertexInputStateBuilder::VertexInputStateBuilder(VertexInputStateBuilder&& other) noexcept
    : elements(std::move(other.elements)),
    description(other.description),
    state(other.state)
{
    state.vertex_buffer_descriptions = &description;
    state.vertex_attributes = elements.data();
}