// Copyright 2023 Google LLC

//

// 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

//

//     https://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 THIRD_PARTY_CEL_CPP_RUNTIME_FUNCTION_PROVIDER_H_

#define THIRD_PARTY_CEL_CPP_RUNTIME_FUNCTION_PROVIDER_H_

#include "absl/status/statusor.h"

#include "common/function_descriptor.h"

#include "runtime/activation_interface.h"

#include "runtime/function_overload_reference.h"

namespace cel::runtime_internal {

// Interface for providers of lazily bound functions.

//

// Lazily bound functions may have an implementation that is dependent on the

// evaluation context (as represented by the Activation).

class FunctionProvider {

 public:

  virtual ~FunctionProvider() = default;

  // Returns a reference to a function implementation based on the provided

  // Activation. Given the same activation, this should return the same Function

  // instance. The cel::FunctionOverloadReference is assumed to be stable for

  // the life of the Activation.

  //

  // An empty optional result is interpreted as no matching overload.

  virtual absl::StatusOr<absl::optional<FunctionOverloadReference>> GetFunction(

      const FunctionDescriptor& descriptor,

      const ActivationInterface& activation) const = 0;

};

}  // namespace cel::runtime_internal

#endif  // THIRD_PARTY_CEL_CPP_RUNTIME_FUNCTION_PROVIDER_H_