// 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_COMMON_FUNCTION_H_

#define THIRD_PARTY_CEL_CPP_COMMON_FUNCTION_H_

#include "absl/base/attributes.h"

#include "absl/base/nullability.h"

#include "absl/status/statusor.h"

#include "absl/types/span.h"

#include "common/value.h"

#include "google/protobuf/arena.h"

#include "google/protobuf/descriptor.h"

#include "google/protobuf/message.h"

namespace cel {

class EmbedderContext;

// Interface for extension functions.

//

// The host for the CEL environment may provide implementations to define custom

// extension functions.

//

// The runtime expects functions to be deterministic and side-effect free.

class Function {

 public:

  virtual ~Function() = default;

  // Context for the function invocation.

  //

  // Collects evaluation state that may be needed for the function to operate.

  //

  // The function implementation should not retain a reference to the context

  // object beyond the duration of the function call or modify the InvokeContext

  // itself.

  class InvokeContext {

   public:

    InvokeContext(

        const google::protobuf::DescriptorPool* absl_nonnull descriptor_pool,

        google::protobuf::MessageFactory* absl_nonnull message_factory,

        google::protobuf::Arena* absl_nonnull arena,

        const EmbedderContext* absl_nullable embedder_context = nullptr)

        : descriptor_pool_(descriptor_pool),

          message_factory_(message_factory),

          arena_(arena),

          embedder_context_(embedder_context) {}

    const google::protobuf::DescriptorPool* absl_nonnull descriptor_pool() const {

      return descriptor_pool_;

    }

    google::protobuf::MessageFactory* absl_nonnull message_factory() const {

      return message_factory_;

    }

    google::protobuf::Arena* absl_nonnull arena() const { return arena_; }

    const EmbedderContext* absl_nullable embedder_context() const {

      return embedder_context_;

    }

    void set_embedder_context(

        const EmbedderContext* absl_nullable embedder_context) {

      embedder_context_ = embedder_context;

    }

   private:

    const google::protobuf::DescriptorPool* absl_nonnull descriptor_pool_;

    google::protobuf::MessageFactory* absl_nonnull message_factory_;

    google::protobuf::Arena* absl_nonnull arena_;

    const EmbedderContext* absl_nullable embedder_context_;

  };

  ABSL_DEPRECATED("Use the InvokeContext overload instead.")

  inline absl::StatusOr<Value> Invoke(

      absl::Span<const Value> args,

      const google::protobuf::DescriptorPool* absl_nonnull descriptor_pool,

      google::protobuf::MessageFactory* absl_nonnull message_factory,

      google::protobuf::Arena* absl_nonnull arena) const;

  // Attempt to evaluate an extension function based on the runtime arguments

  // during the evaluation of a CEL expression.

  //

  // A non-ok status is interpreted as an unrecoverable error in evaluation (

  // e.g. data corruption). This stops evaluation and is propagated immediately.

  //

  // A cel::ErrorValue typed result is considered a recoverable error and

  // follows CEL's logical short-circuiting behavior.

  virtual absl::StatusOr<Value> Invoke(absl::Span<const Value> args,

                                       const InvokeContext& context) const = 0;

};

absl::StatusOr<Value> Function::Invoke(

    absl::Span<const Value> args,

    const google::protobuf::DescriptorPool* absl_nonnull descriptor_pool,

    google::protobuf::MessageFactory* absl_nonnull message_factory,

    google::protobuf::Arena* absl_nonnull arena) const {

  InvokeContext context(descriptor_pool, message_factory, arena);

  return Invoke(args, context);

}

}  // namespace cel

#endif  // THIRD_PARTY_CEL_CPP_COMMON_FUNCTION_H_