/*
Crafter®.Graphics
Copyright (C) 2026 Catcrafts®
catcrafts.net
*/

// WebGPU buffer wrapper — DOM-mode parallel to VulkanBuffer<T, Mapped>.
// Holds a JS-side GPUBuffer handle + (when Mapped) a wasm-memory staging
// array. `.value` points to the staging memory; the user writes into it
// directly, and `.Flush(cmd)` copies to the GPU via queue.writeBuffer.

export module Crafter.Graphics:WebGPUBuffer;
#ifdef CRAFTER_GRAPHICS_WINDOW_DOM
import std;
import :WebGPU;

export namespace Crafter {
    class WebGPUBufferBase {
    public:
        WebGPUBufferRef handle = 0;
        std::uint32_t size = 0;   // bytes
    };

    template<typename T>
    class WebGPUBufferMapped {
    public:
        T* value = nullptr;
    };
    class WebGPUBufferMappedEmpty {};

    template<typename T, bool Mapped>
    using WebGPUBufferMappedConditional =
        std::conditional_t<Mapped, WebGPUBufferMapped<T>, WebGPUBufferMappedEmpty>;

    template<typename T, bool Mapped>
    class WebGPUBuffer : public WebGPUBufferBase, public WebGPUBufferMappedConditional<T, Mapped> {
    public:
        WebGPUBuffer() = default;
        WebGPUBuffer(const WebGPUBuffer&) = delete;
        WebGPUBuffer& operator=(const WebGPUBuffer&) = delete;

        WebGPUBuffer(WebGPUBuffer&& other) noexcept {
            handle = other.handle;
            size   = other.size;
            other.handle = 0;
            if constexpr (Mapped) {
                this->value = other.value;
                other.value = nullptr;
            }
        }

        void Create(std::uint32_t count) {
            size = static_cast<std::uint32_t>(count * sizeof(T));
            handle = WebGPU::wgpuCreateBuffer(static_cast<std::int32_t>(size));
            if constexpr (Mapped) {
                this->value = new T[count]();
            }
        }

        void Clear() {
            if (handle != 0) {
                WebGPU::wgpuDestroyBuffer(handle);
                handle = 0;
            }
            if constexpr (Mapped) {
                if (this->value) { delete[] this->value; this->value = nullptr; }
            }
        }

        void Resize(std::uint32_t count) {
            if (handle != 0) Clear();
            Create(count);
        }

        void Flush(WebGPUCommandEncoderRef /*cmd*/) requires(Mapped) {
            WebGPU::wgpuWriteBuffer(handle, this->value, static_cast<std::int32_t>(size));
        }
        void FlushDevice() requires(Mapped) {
            WebGPU::wgpuWriteBuffer(handle, this->value, static_cast<std::int32_t>(size));
        }

        ~WebGPUBuffer() { Clear(); }
    };
}
#endif // CRAFTER_GRAPHICS_WINDOW_DOM