#ifndef __LOCK_FREE_QUEUE_H__
#define __LOCK_FREE_QUEUE_H__

#include <usg_common.h>
#include <assert.h> // assert()
#include "mem_pool.h"
#include "sem_util.h"
#include "logger_factory.h"
#include "shm_allocator.h"

// default Queue size
#define LOCK_FREE_Q_DEFAULT_SIZE 16

// define this macro if calls to "size" must return the real size of the 
// queue. If it is undefined  that function will try to take a snapshot of 
// the queue, but returned value might be bogus


// forward declarations for default template values
//

template <typename ELEM_T, typename Allocator>
class ArrayLockFreeQueue;

// template <typename ELEM_T>
// class LinkedLockFreeQueue;


/// @brief Lock-free queue based on a circular array
/// No allocation of extra memory for the nodes handling is needed, but it has 
/// to add extra overhead (extra CAS operation) when inserting to ensure the 
/// thread-safety of the queue when the queue type is not 
/// ArrayLockFreeQueueSingleProducer.
///
/// examples of instantiation:
///   ArrayLockFreeQueue<int> q; // queue of ints of default size (65535 - 1)
///                              // and defaulted to single producer
///   ArrayLockFreeQueue<int, 16> q;
///                              // queue of ints of size (16 - 1) and
///                              // defaulted to single producer
///   ArrayLockFreeQueue<int, 100, ArrayLockFreeQueue> q;
///                              // queue of ints of size (100 - 1) with support
///                              // for multiple producers
///
/// ELEM_T represents the type of elementes pushed and popped from the queue
/// Q_SIZE size of the queue. The actual size of the queue is (Q_SIZE-1)
///        This number should be a power of 2 to ensure 
///        indexes in the circular queue keep stable when the uint32_t 
///        variable that holds the current position rolls over from FFFFFFFF
///        to 0. For instance
///        2    -> 0x02 
///        4    -> 0x04
///        8    -> 0x08
///        16   -> 0x10
///        (...) 
///        1024 -> 0x400
///        2048 -> 0x800
///
///        if queue size is not defined as requested, let's say, for
///        instance 100, when current position is FFFFFFFF (4,294,967,295)
///        index in the circular array is 4,294,967,295 % 100 = 95. 
///        When that value is incremented it will be set to 0, that is the 
///        last 4 elements of the queue are not used when the counter rolls
///        over to 0
/// Q_TYPE type of queue implementation. ArrayLockFreeQueueSingleProducer and 
///        ArrayLockFreeQueue are supported (single producer
///        by default)
template <
    typename ELEM_T, 
    typename Allocator = SHM_Allocator,
    template <typename T, typename AT> class Q_TYPE = ArrayLockFreeQueue
     >
class LockFreeQueue
{

private:
    int slots;
    int items;
   
public:
    int mutex;
    LockFreeQueue(size_t qsize = LOCK_FREE_Q_DEFAULT_SIZE);
    
    /// @brief destructor of the class. 
    /// Note it is not virtual since it is not expected to inherit from this
    /// template
    ~LockFreeQueue();
    std::atomic_uint reference;    
    /// @brief constructor of the class
   

    /// @brief returns the current number of items in the queue
    /// It tries to take a snapshot of the size of the queue, but in busy environments
    /// this function might return bogus values. 
    ///
    /// If a reliable queue size must be kept you might want to have a look at 
    /// the preprocessor variable in this header file called '_WITH_LOCK_FREE_Q_KEEP_REAL_SIZE'
    /// it enables a reliable size though it hits overall performance of the queue 
    /// (when the reliable size variable is on it's got an impact of about 20% in time)
    inline uint32_t size();
    
    /// @brief return true if the queue is full. False otherwise
    /// It tries to take a snapshot of the size of the queue, but in busy 
    /// environments this function might return bogus values. See help in method
    /// LockFreeQueue::size
    inline bool full();

    inline bool empty();

    inline ELEM_T& operator[](unsigned i);

    /// @brief push an element at the tail of the queue
    /// @param the element to insert in the queue
    /// Note that the element is not a pointer or a reference, so if you are using large data
    /// structures to be inserted in the queue you should think of instantiate the template
    /// of the queue as a pointer to that large structure
    /// @return true if the element was inserted in the queue. False if the queue was full
    bool push(const ELEM_T &a_data);
    bool push_nowait(const ELEM_T &a_data);
    bool push_timeout(const ELEM_T &a_data, const struct timespec * timeout);

    /// @brief pop the element at the head of the queue
    /// @param a reference where the element in the head of the queue will be saved to
    /// Note that the a_data parameter might contain rubbish if the function returns false
    /// @return true if the element was successfully extracted from the queue. False if the queue was empty
    bool pop(ELEM_T &a_data);
    bool pop_nowait(ELEM_T &a_data);
    bool pop_timeout(ELEM_T &a_data, struct timespec * timeout);


    void *operator new(size_t size);
    void operator delete(void *p);

protected:
    /// @brief the actual queue. methods are forwarded into the real 
    ///        implementation
    Q_TYPE<ELEM_T, Allocator> m_qImpl;

private:
    /// @brief disable copy constructor declaring it private
    LockFreeQueue<ELEM_T, Allocator, Q_TYPE>(const LockFreeQueue<ELEM_T, Allocator, Q_TYPE> &a_src);
};


template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::LockFreeQueue(size_t qsize): reference(0), m_qImpl(qsize)
{
// std::cout << "LockFreeQueue init reference=" << reference << std::endl;
    slots = SemUtil::get(IPC_PRIVATE, qsize);
    items = SemUtil::get(IPC_PRIVATE, 0);
    mutex = SemUtil::get(IPC_PRIVATE, 1);
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::~LockFreeQueue()
{
    LoggerFactory::getLogger().debug("LockFreeQueue desctroy");
    SemUtil::remove(slots);
    SemUtil::remove(items);
    SemUtil::remove(mutex);
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
inline uint32_t LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::size()
{
    return m_qImpl.size();
}  

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
inline bool LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::full()
{
    return m_qImpl.full();
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
inline bool LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::empty()
{
    return m_qImpl.empty();
}  


template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
bool LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::push(const ELEM_T &a_data)
{
 // printf("==================LockFreeQueue push before\n");   
    if (SemUtil::dec(slots) == -1) {
        err_msg(errno, "LockFreeQueue push");
        return false;
    }

    if ( m_qImpl.push(a_data) ) {

        SemUtil::inc(items);   
 // printf("==================LockFreeQueue push after\n");   
        return true;
    }
    return false;
    
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
bool LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::push_nowait(const ELEM_T &a_data)
{
    if (SemUtil::dec_nowait(slots) == -1) {
        if (errno == EAGAIN)
            return false;
        else {
            err_msg(errno, "LockFreeQueue push_nowait");
            return false;
        }

    }

    if ( m_qImpl.push(a_data)) {
        SemUtil::inc(items);     
        return true;
    }
    return false;
    
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
bool LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::push_timeout(const ELEM_T &a_data, const struct timespec * timeout)
{


    if (SemUtil::dec_timeout(slots, timeout) == -1) {
        if (errno == EAGAIN)
            return false;
        else {
            // err_msg(errno, "LockFreeQueue push_timeout");
            return false;
        }
    }

    if (m_qImpl.push(a_data)){
        SemUtil::inc(items);       
        return true;
    }
    return false;
    
}




template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
bool LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::pop(ELEM_T &a_data)
{
 // printf("==================LockFreeQueue pop before\n");
    if (SemUtil::dec(items) == -1) {
        err_msg(errno, "LockFreeQueue pop");
        return false;
    }

    if (m_qImpl.pop(a_data)) {
        SemUtil::inc(slots);
 // printf("==================LockFreeQueue pop after\n");      
        return true;
    }
    return false;
    
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
bool LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::pop_nowait(ELEM_T &a_data)
{
    if (SemUtil::dec_nowait(items) == -1) {
        if (errno == EAGAIN)
            return false;
        else {
            err_msg(errno, "LockFreeQueue pop_nowait");
            return false;
        }
    }

    if (m_qImpl.pop(a_data)) {
        SemUtil::inc(slots);     
        return true;
    }
    return false;
    
}

 
template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
bool LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::pop_timeout(ELEM_T &a_data, struct timespec * timeout)
{
// printf("==================LockFreeQueue pop_timeout before\n");
    if (SemUtil::dec_timeout(items, timeout) == -1) {
        if (errno == EAGAIN)
            return false;
        else {
            // err_msg(errno, "LockFreeQueue pop_timeout");
            return false;
        }
    }

    if (m_qImpl.pop(a_data)) {
        SemUtil::inc(slots);  
// printf("==================LockFreeQueue pop_timeout after\n");     
        return true;
    }
    return false;
    
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
ELEM_T& LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::operator[](unsigned i) {
    return m_qImpl.operator[](i);
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
void * LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::operator new(size_t size){
        return Allocator::allocate(size);
}

template <
    typename ELEM_T, 
    typename Allocator,
    template <typename T, typename AT> class Q_TYPE>
void LockFreeQueue<ELEM_T, Allocator, Q_TYPE>::operator delete(void *p) {
    return Allocator::deallocate(p);
}

// include implementation files
//#include "linked_lock_free_queue.h"
#include "array_lock_free_queue.h"

#endif // _LOCK_FREE_QUEUE_H__