// Copyright 2017 The NXT Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "backend/d3d12/ResourceUploader.h"

#include "backend/d3d12/D3D12Backend.h"
#include "backend/d3d12/ResourceAllocator.h"

namespace backend {
namespace d3d12 {

    ResourceUploader::ResourceUploader(Device* device) : device(device) {
    }

    void ResourceUploader::BufferSubData(ComPtr<ID3D12Resource> resource, uint32_t start, uint32_t count, const void* data) {
        // TODO(enga@google.com): Use a handle to a subset of a large ring buffer. On Release, decrease reference count on the ring buffer and free when 0.
        // Alternatively, the SerialQueue could be used to track which last point of the ringbuffer is in use, and start reusing chunks of it that aren't in flight.
        UploadHandle uploadHandle = GetUploadBuffer(count);
        memcpy(uploadHandle.mappedBuffer, data, count);
        device->GetPendingCommandList()->CopyBufferRegion(resource.Get(), start, uploadHandle.resource.Get(), 0, count);
        Release(uploadHandle);
    }

    ResourceUploader::UploadHandle ResourceUploader::GetUploadBuffer(uint32_t requiredSize) {
        // TODO(enga@google.com): This will find or create a mapped buffer of sufficient size and return a handle to a mapped range
        D3D12_RESOURCE_DESC resourceDescriptor;
        resourceDescriptor.Dimension = D3D12_RESOURCE_DIMENSION_BUFFER;
        resourceDescriptor.Alignment = 0;
        resourceDescriptor.Width = requiredSize;
        resourceDescriptor.Height = 1;
        resourceDescriptor.DepthOrArraySize = 1;
        resourceDescriptor.MipLevels = 1;
        resourceDescriptor.Format = DXGI_FORMAT_UNKNOWN;
        resourceDescriptor.SampleDesc.Count = 1;
        resourceDescriptor.SampleDesc.Quality = 0;
        resourceDescriptor.Layout = D3D12_TEXTURE_LAYOUT_ROW_MAJOR;
        resourceDescriptor.Flags = D3D12_RESOURCE_FLAG_NONE;

        UploadHandle uploadHandle;
        uploadHandle.resource = device->GetResourceAllocator()->Allocate(D3D12_HEAP_TYPE_UPLOAD, resourceDescriptor, D3D12_RESOURCE_STATE_GENERIC_READ);
        D3D12_RANGE readRange;
        readRange.Begin = 0;
        readRange.End = 0;

        uploadHandle.resource->Map(0, &readRange, reinterpret_cast<void**>(&uploadHandle.mappedBuffer));
        return uploadHandle;
    }

    void ResourceUploader::Release(UploadHandle uploadHandle) {
        uploadHandle.resource->Unmap(0, nullptr);
        device->GetResourceAllocator()->Release(uploadHandle.resource);
    }

}
}