// Copyright 2022 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_BASE_ATTRIBUTE_SET_H_

#define THIRD_PARTY_CEL_CPP_BASE_ATTRIBUTE_SET_H_

#include <memory>

#include "absl/base/no_destructor.h"

#include "absl/container/btree_set.h"

#include "absl/types/span.h"

#include "base/attribute.h"

namespace google::api::expr::runtime {

class AttributeUtility;

}  // namespace google::api::expr::runtime

namespace cel {

class UnknownValue;

namespace base_internal {

class UnknownSet;

}

// AttributeSet is a container for CEL attributes that are identified as

// unknown during expression evaluation.

class AttributeSet final {

 private:

  using Container = absl::btree_set<Attribute>;

 public:

  using value_type = typename Container::value_type;

  using size_type = typename Container::size_type;

  using iterator = typename Container::const_iterator;

  using const_iterator = typename Container::const_iterator;

  AttributeSet() = default;

  AttributeSet(const AttributeSet&) = default;

  AttributeSet(AttributeSet&&) = default;

  AttributeSet& operator=(const AttributeSet&) = default;

  AttributeSet& operator=(AttributeSet&&) = default;

  explicit AttributeSet(absl::Span<const Attribute> attributes) {

    for (const auto& attr : attributes) {

      Add(attr);

    }

  }

  AttributeSet(const AttributeSet& set1, const AttributeSet& set2) {

    Add(set1);

    Add(set2);

  }

  iterator begin() const {

    return attributes_ != nullptr ? attributes_->begin()

                                  : EmptyContainer().begin();

  }

  const_iterator cbegin() const {

    return attributes_ != nullptr ? attributes_->cbegin()

                                  : EmptyContainer().cbegin();

  }

  iterator end() const {

    return attributes_ != nullptr ? attributes_->end() : EmptyContainer().end();

  }

  const_iterator cend() const {

    return attributes_ != nullptr ? attributes_->cend()

                                  : EmptyContainer().cend();

  }

  size_type size() const {

    return attributes_ != nullptr ? attributes_->size() : 0;

  }

  bool empty() const { return attributes_ == nullptr || attributes_->empty(); }

  bool operator==(const AttributeSet& other) const {

    if (attributes_ == other.attributes_) {

      return true;

    }

    return (attributes_ != nullptr ? *attributes_ : EmptyContainer()) ==

           (other.attributes_ != nullptr ? *other.attributes_

                                         : EmptyContainer());

  }

  bool operator!=(const AttributeSet& other) const {

    return !operator==(other);

  }

  static AttributeSet Merge(const AttributeSet& set1,

                            const AttributeSet& set2) {

    return AttributeSet(set1, set2);

  }

 private:

  friend class google::api::expr::runtime::AttributeUtility;

  friend class UnknownValue;

  friend class base_internal::UnknownSet;

  static const Container& EmptyContainer() {

    static const absl::NoDestructor<Container> container;

    return *container;

  }

  void Add(const Attribute& attribute) {

    if (attributes_ == nullptr) {

      attributes_ = std::make_shared<Container>();

    }

    attributes_->insert(attribute);

  }

  void Add(const AttributeSet& other) {

    if (!other.empty()) {

      if (attributes_ == nullptr) {

        attributes_ = std::make_shared<Container>();

      }

      for (const auto& attribute : other) {

        attributes_->insert(attribute);

      }

    }

  }

  // Attribute container.

  std::shared_ptr<Container> attributes_;

};

}  // namespace cel

#endif  // THIRD_PARTY_CEL_CPP_BASE_ATTRIBUTE_SET_H_