// Copyright 2025 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_EVAL_EVAL_ITERATOR_STACK_H_

#define THIRD_PARTY_CEL_CPP_EVAL_EVAL_ITERATOR_STACK_H_

#include <cstddef>

#include <utility>

#include <vector>

#include "absl/base/nullability.h"

#include "absl/log/absl_check.h"

#include "common/value.h"

namespace cel::runtime_internal {

class IteratorStack final {

 public:

  explicit IteratorStack(size_t max_size) : max_size_(max_size) {

    iterators_.reserve(max_size_);

  }

  IteratorStack(const IteratorStack&) = delete;

  IteratorStack(IteratorStack&&) = delete;

  IteratorStack& operator=(const IteratorStack&) = delete;

  IteratorStack& operator=(IteratorStack&&) = delete;

  size_t size() const { return iterators_.size(); }

  bool empty() const { return iterators_.empty(); }

  bool full() const { return iterators_.size() == max_size_; }

  size_t max_size() const { return max_size_; }

  void Clear() { iterators_.clear(); }

  void Push(absl_nonnull ValueIteratorPtr iterator) {

    ABSL_DCHECK(!full());

    ABSL_DCHECK(iterator != nullptr);

    iterators_.push_back(std::move(iterator));

  }

  ValueIterator* absl_nonnull Peek() {

    ABSL_DCHECK(!empty());

    ABSL_DCHECK(iterators_.back() != nullptr);

    return iterators_.back().get();

  }

  void Pop() {

    ABSL_DCHECK(!empty());

    iterators_.pop_back();

  }

 private:

  std::vector<absl_nonnull ValueIteratorPtr> iterators_;

  size_t max_size_;

};

}  // namespace cel::runtime_internal

#endif  // THIRD_PARTY_CEL_CPP_EVAL_EVAL_ITERATOR_STACK_H_