IndexGPUBuffer.hpp

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#pragma once
 
#include "component/Mesh.hpp"
#include "entity/Entity.hpp"
#include "exception/NonexistentComponentError.hpp"
#include "exception/UpdateBufferError.hpp"
#include "resource/AGPUBuffer.hpp"
#include "resource/DeviceContext.hpp"
#include "resource/Queue.hpp"
 
namespace DefaultPipeline::Resource {
class IndexGPUBuffer : public Graphic::Resource::AGPUBuffer {
  public:
    explicit IndexGPUBuffer(Engine::Entity entity) : _entity(entity) {}
    ~IndexGPUBuffer() override { Destroy(); }
    void Create(Engine::Core &core) override
    {
 
        auto meshComponent = _entity.TryGetComponent<Object::Component::Mesh>();
 
        if (!meshComponent)
        {
            throw Graphic::Exception::NonexistentComponentError(
                "Cannot create a GPU buffer for an entity without a Mesh component.");
        }
 
        const auto &indices = meshComponent->GetIndices();
 
        wgpu::BufferDescriptor bufferDesc(wgpu::Default);
        bufferDesc.usage = wgpu::BufferUsage::CopyDst | wgpu::BufferUsage::Index;
        bufferDesc.size = sizeof(uint32_t) * indices.size();
        std::string label = fmt::format("IndexGPUBuffer_{}", _entity);
        bufferDesc.label = wgpu::StringView(label);
 
        const auto &deviceContext = core.GetResource<Graphic::Resource::DeviceContext>();
        const auto &queue = core.GetResource<Graphic::Resource::Queue>();
 
        _buffer = deviceContext.GetDevice()->createBuffer(bufferDesc);
 
        queue->writeBuffer(_buffer, 0, indices.data(), bufferDesc.size);
 
        _isCreated = true;
    };
    void Destroy(Engine::Core &core) override { Destroy(); };
 
    void Destroy()
    {
        if (_isCreated)
        {
            _isCreated = false;
            _buffer.release();
        }
    }
 
    bool IsCreated(Engine::Core &core) const override { return _isCreated; };
    void Update(Engine::Core &core) override
    {
        if (!_isCreated)
        {
            throw Graphic::Exception::UpdateBufferError("Cannot update a GPU buffer that is not created.");
        }
 
        auto &meshComponent = _entity.GetComponents<Object::Component::Mesh>();
 
        // For now, we will not implement dynamic resizing of the buffer. As we should have a way to know if the size
        // changed. And it would be so heavy to check every frame every index.
    };
 
    const wgpu::Buffer &GetBuffer() const override { return _buffer; };
 
  private:
    wgpu::Buffer _buffer;
    bool _isCreated = false;
    Engine::Entity _entity;
};
} // namespace DefaultPipeline::Resource