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//

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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// A sample program demonstrating using Google C++ testing framework.

//

// Author: wan@google.com (Zhanyong Wan)

#ifndef GTEST_SAMPLES_SAMPLE3_INL_H_

#define GTEST_SAMPLES_SAMPLE3_INL_H_

#include <stddef.h>

// Queue is a simple queue implemented as a singled-linked list.

//

// The element type must support copy constructor.

template <typename E>  // E is the element type

class Queue;

// QueueNode is a node in a Queue, which consists of an element of

// type E and a pointer to the next node.

template <typename E>  // E is the element type

class QueueNode {

  friend class Queue<E>;

 public:

  // Gets the element in this node.

  const E& element() const { return element_; }

  // Gets the next node in the queue.

  QueueNode* next() { return next_; }

  const QueueNode* next() const { return next_; }

 private:

  // Creates a node with a given element value.  The next pointer is

  // set to NULL.

  explicit QueueNode(const E& an_element) : element_(an_element), next_(NULL) {}

  // We disable the default assignment operator and copy c'tor.

  const QueueNode& operator = (const QueueNode&);

  QueueNode(const QueueNode&);

  E element_;

  QueueNode* next_;

};

template <typename E>  // E is the element type.

class Queue {

 public:

  // Creates an empty queue.

  Queue() : head_(NULL), last_(NULL), size_(0) {}

  // D'tor.  Clears the queue.

  ~Queue() { Clear(); }

  // Clears the queue.

  void Clear() {

    if (size_ > 0) {

      // 1. Deletes every node.

      QueueNode<E>* node = head_;

      QueueNode<E>* next = node->next();

      for (; ;) {

        delete node;

        node = next;

        if (node == NULL) break;

        next = node->next();

      }

      // 2. Resets the member variables.

      head_ = last_ = NULL;

      size_ = 0;

    }

  }

  // Gets the number of elements.

  size_t Size() const { return size_; }

  // Gets the first element of the queue, or NULL if the queue is empty.

  QueueNode<E>* Head() { return head_; }

  const QueueNode<E>* Head() const { return head_; }

  // Gets the last element of the queue, or NULL if the queue is empty.

  QueueNode<E>* Last() { return last_; }

  const QueueNode<E>* Last() const { return last_; }

  // Adds an element to the end of the queue.  A copy of the element is

  // created using the copy constructor, and then stored in the queue.

  // Changes made to the element in the queue doesn't affect the source

  // object, and vice versa.

  void Enqueue(const E& element) {

    QueueNode<E>* new_node = new QueueNode<E>(element);

    if (size_ == 0) {

      head_ = last_ = new_node;

      size_ = 1;

    } else {

      last_->next_ = new_node;

      last_ = new_node;

      size_++;

    }

  }

  // Removes the head of the queue and returns it.  Returns NULL if

  // the queue is empty.

  E* Dequeue() {

    if (size_ == 0) {

      return NULL;

    }

    const QueueNode<E>* const old_head = head_;

    head_ = head_->next_;

    size_--;

    if (size_ == 0) {

      last_ = NULL;

    }

    E* element = new E(old_head->element());

    delete old_head;

    return element;

  }

  // Applies a function/functor on each element of the queue, and

  // returns the result in a new queue.  The original queue is not

  // affected.

  template <typename F>

  Queue* Map(F function) const {

    Queue* new_queue = new Queue();

    for (const QueueNode<E>* node = head_; node != NULL; node = node->next_) {

      new_queue->Enqueue(function(node->element()));

    }

    return new_queue;

  }

 private:

  QueueNode<E>* head_;  // The first node of the queue.

  QueueNode<E>* last_;  // The last node of the queue.

  size_t size_;  // The number of elements in the queue.

  // We disallow copying a queue.

  Queue(const Queue&);

  const Queue& operator = (const Queue&);

};

#endif  // GTEST_SAMPLES_SAMPLE3_INL_H_