// Copyright 2019 The Dawn 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.

#ifndef SRC_DAWN_NATIVE_D3D12_BACKENDD3D12_H_
#define SRC_DAWN_NATIVE_D3D12_BACKENDD3D12_H_

#include <memory>
#include <string>
#include <variant>
#include <vector>

#include "dawn/native/BackendConnection.h"

#include "dawn/native/d3d12/d3d12_platform.h"

namespace dawn::native::d3d12 {

class PlatformFunctions;

// DxcVersionInfo holds both DXC compiler (dxcompiler.dll) version and DXC validator (dxil.dll)
// version, which are not necessarily identical. Both are in uint64_t type, as the result of
// MakeDXCVersion.
struct DxcVersionInfo {
    uint64_t DxcCompilerVersion;
    uint64_t DxcValidatorVersion;
};

// If DXC version information is not avaliable due to no DXC binary or error occurs when acquiring
// version, DxcUnavailable indicates the version information being unavailable and holds the
// detailed error information.
struct DxcUnavailable {
    std::string ErrorMessage;
};

class Backend : public BackendConnection {
  public:
    explicit Backend(InstanceBase* instance);

    MaybeError Initialize();

    ComPtr<IDXGIFactory4> GetFactory() const;

    MaybeError EnsureDxcLibrary();
    MaybeError EnsureDxcCompiler();
    MaybeError EnsureDxcValidator();
    ComPtr<IDxcLibrary> GetDxcLibrary() const;
    ComPtr<IDxcCompiler> GetDxcCompiler() const;
    ComPtr<IDxcValidator> GetDxcValidator() const;

    // Return true if and only if DXC binary is avaliable, and the DXC compiler and validator
    // version are validated to be no older than a specific minimium version, currently 1.6.
    bool IsDXCAvailable() const;

    // Return true if and only if mIsDXCAvailable is true, and the DXC compiler and validator
    // version are validated to be no older than the minimium version given in parameter.
    bool IsDXCAvailableAndVersionAtLeast(uint64_t minimumCompilerMajorVersion,
                                         uint64_t minimumCompilerMinorVersion,
                                         uint64_t minimumValidatorMajorVersion,
                                         uint64_t minimumValidatorMinorVersion) const;

    // Return the DXC version information cached in mDxcVersionInformation, assert that the version
    // information is valid. Must be called after ensuring `IsDXCAvailable()` return true.
    DxcVersionInfo GetDxcVersion() const;

    const PlatformFunctions* GetFunctions() const;

    std::vector<Ref<AdapterBase>> DiscoverDefaultAdapters() override;
    ResultOrError<std::vector<Ref<AdapterBase>>> DiscoverAdapters(
        const AdapterDiscoveryOptionsBase* optionsBase) override;

  private:
    // Acquiring DXC version information and store the result in mDxcVersionInfo. This function
    // should be called only once, during startup in `Initialize`.
    void AcquireDxcVersionInformation();

    // Keep mFunctions as the first member so that in the destructor it is freed last. Otherwise
    // the D3D12 DLLs are unloaded before we are done using them.
    std::unique_ptr<PlatformFunctions> mFunctions;
    ComPtr<IDXGIFactory4> mFactory;
    ComPtr<IDxcLibrary> mDxcLibrary;
    ComPtr<IDxcCompiler> mDxcCompiler;
    ComPtr<IDxcValidator> mDxcValidator;

    // DXC binaries and DXC version information are checked when start up in `Initialize`. There are
    // two possible states:
    //   1. The DXC binary is not available, or error occurs when checking the version information
    //      and therefore no DXC version information available, or the DXC version is lower than
    //      requested minumum and therefore DXC is not available, represented by DxcUnavailable
    //      in which a error message is held;
    //   3. The DXC version information is acquired successfully and validated not lower than
    //      requested minimum, stored in DxcVersionInfo.
    std::variant<DxcUnavailable, DxcVersionInfo> mDxcVersionInfo;
};

}  // namespace dawn::native::d3d12

#endif  // SRC_DAWN_NATIVE_D3D12_BACKENDD3D12_H_