BLT/include/blt/std/queue.h

/*
 * Created by Brett on 26/12/22.
 * Licensed under GNU General Public License V3.0
 * See LICENSE file for license detail
 */

#ifndef BLT_QUEUE_H
#define BLT_QUEUE_H

/**
 *
 */
namespace blt
{
    
    /**
     * Standard array backed first in first out queue
     * @tparam T type stored in the queue
     */
    template<typename T>
    class flat_stack
    {
        private:
            int m_size = 16;
            int m_insertIndex = 0;
            T* m_data = new T[m_size];
            
            /**
             * Expands the internal array to the new size, copying over the data and shifting its minimal position to index 0
             * and deletes the old array from memory.
             * @param newSize new size of the internal array
             */
            void expand()
            {
                int new_size = m_size * 2;
                auto tempData = new T[new_size];
                for (int i = 0; i < m_insertIndex; i++)
                    tempData[i] = m_data[i];
                delete[] m_data;
                m_data = tempData;
                m_size = new_size;
            }
        
        public:
            
            void push(const T& t)
            {
                if (m_insertIndex >= m_size)
                {
                    expand();
                }
                m_data[m_insertIndex++] = t;
            }
            
            /**
             * Warning does not contain runtime error checking!
             * @return the element at the "front" of the queue.
             */
            [[nodiscard]] const T& top() const
            {
                return m_data[m_insertIndex - 1];
            }
            
            void pop()
            {
                if (empty())
                    return;
                m_insertIndex--;
            }
            
            [[nodiscard]] inline bool empty() const
            {
                return m_insertIndex <= 0;
            }
            
            [[nodiscard]] inline int size() const
            {
                return m_insertIndex;
            }
            
            ~flat_stack()
            {
                delete[](m_data);
            }
    };
    
    /**
     * Standard array backed first in last out queue (stack)
     * @tparam T type stored in the queue
     */
    template<typename T>
    class flat_queue
    {
        private:
            int m_size = 16;
            int m_headIndex = 0;
            int m_insertIndex = 0;
            T* m_data;
            
            /**
             * Expands the internal array to allow for more storage of elements
             */
            void expand()
            {
                int new_size = m_size * 2;
                int removed_size = m_size - m_headIndex;
                auto tempData = new T[new_size];
                // only copy data from where we've removed onward
                for (int i = 0; i < removed_size; i++)
                    tempData[i] = m_data[i + m_headIndex]; // but don't copy data we've pop'd
                delete[] m_data;
                m_headIndex = 0;
                m_insertIndex = removed_size - 1;
                m_data = tempData;
                m_size = new_size;
            }
        
        public:
            flat_queue(): m_data(new T[m_size])
            {
            
            }
            
            inline void push(const T& t)
            {
                if (m_insertIndex + 1 >= m_size)
                {
                    expand();
                }
                m_data[m_insertIndex++] = t;
            }
            
            /**
             * Warning does not contain runtime error checking!
             * @return the element at the "front" of the queue.
             */
            [[nodiscard]] const T& front() const
            {
                return m_data[m_headIndex];
            }
            
            [[nodiscard]] T& front()
            {
                return m_data[m_headIndex];
            }
            
            inline void pop()
            {
                if (empty())
                    return;
                m_headIndex++;
            }
            
            [[nodiscard]] inline bool empty() const
            {
                return m_headIndex >= m_size;
            }
            
            [[nodiscard]] inline int size() const
            {
                return m_insertIndex - m_headIndex;
            }
            
            inline T* begin()
            {
                return m_data[m_headIndex];
            }
            
            inline T* end()
            {
                return m_data[m_insertIndex];
            }
            
            ~flat_queue()
            {
                delete[](m_data);
            }
    };
    
    template<typename T>
    class linked_stack
    {
        private:
            struct node
            {
                T t;
                node* next;
                
                node(const T& t, node* node): t(t), next(node)
                {}
                
                node(T&& t, node* node): t(std::move(t)), next(node)
                {}
            };
            
            node* head = nullptr;
        public:
            inline void push(const T& t)
            {
                head = new node(t, head);
            }
            
            inline void push(T&& t)
            {
                head = new node(std::move(t), head);
            }
            
            inline T& top()
            {
                return head->t;
            }
            
            
            inline const T& top() const
            {
                return head->t;
            }
            
            inline void pop()
            {
                auto* h = head;
                head = head->next;
                delete h;
            }
            
            ~linked_stack()
            {
                auto* h = head;
                while (h != nullptr)
                {
                    auto* hc = h;
                    h = h->next;
                    delete hc;
                }
            }
    };
}

#endif //BLT_QUEUE_H