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// 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_
