/*
 * =====================================================================================
 *
 *       Filename:  robust.h
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  2021年04月27日 10时04分29秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Li Chao (), lichao@aiotlink.com
 *   Organization:  
 *
 * =====================================================================================
 */

#ifndef ROBUST_Q31RCWYU
#define ROBUST_Q31RCWYU

#include "bh_util.h"
#include "log.h"
#include <atomic>
#include <chrono>
#include <unistd.h>

namespace robust
{
/*
template <unsigned PowerSize = 4, class Int = int64_t>
class AtomicQueue
{
public:
	typedef uint32_t size_type;
	typedef Int Data;
	typedef std::atomic<Data> AData;
	static_assert(sizeof(Data) == sizeof(AData));
	enum {
		power = PowerSize,
		capacity = (1 << power),
		mask = capacity - 1,
	};

	AtomicQueue() { memset(this, 0, sizeof(*this)); }
	size_type head() const { return head_.load(); }
	size_type tail() const { return tail_.load(); }
	bool push(const Data d, bool try_more = false)
	{
		bool r = false;
		size_type i = 0;
		do {
			auto pos = tail();
			if (tail_.compare_exchange_strong(pos, Next(pos))) {
				auto cur = buf[pos].load();
				r = Empty(cur) && buf[pos].compare_exchange_strong(cur, Enc(d));
			}
		} while (try_more && !r && ++i < capacity);
		return r;
	}
	bool pop(Data &d, bool try_more = false)
	{
		bool r = false;
		Data cur;
		size_type i = 0;
		do {
			auto pos = head();
			if (head_.compare_exchange_strong(pos, Next(pos))) {
				cur = buf[pos].load();
				r = !Empty(cur) && buf[pos].compare_exchange_strong(cur, 0);
			}
		} while (try_more && !r && ++i < capacity);
		if (r) { d = Dec(cur); }
		return r;
	}

private:
	static_assert(std::is_integral<Data>::value, "Data must be integral type!");
	static_assert(std::is_signed<Data>::value, "Data must be signed type!");
	static_assert(PowerSize < 10, "RobustQ63 max size is 2^10!");

	static inline bool Empty(const Data d) { return (d & 1) == 0; } // lowest bit 1 means data ok.
	static inline Data Enc(const Data d) { return (d << 1) | 1; }   // lowest bit 1 means data ok.
	static inline Data Dec(const Data d) { return d >> 1; }         // lowest bit 1 means data ok.
	static size_type Next(const size_type index) { return (index + 1) & mask; }

	std::atomic<size_type> head_;
	std::atomic<size_type> tail_;
	AData buf[capacity];
};
//*/

class AtomicQ63
{
public:
	typedef int64_t Data;
	AtomicQ63() { memset(this, 0, sizeof(*this)); }
	bool push(const Data d, bool try_more = false)
	{
		auto cur = buf.load();
		return Empty(cur) && buf.compare_exchange_strong(cur, Enc(d));
	}
	bool pop(Data &d, bool try_more = false)
	{
		Data cur = buf.load();
		bool r = !Empty(cur) && buf.compare_exchange_strong(cur, 0);
		if (r) { d = Dec(cur); }
		return r;
	}

private:
	static inline bool Empty(const Data d) { return (d & 1) == 0; } // lowest bit 1 means data ok.
	static inline Data Enc(const Data d) { return (d << 1) | 1; }   // lowest bit 1 means data ok.
	static inline Data Dec(const Data d) { return d >> 1; }         // lowest bit 1 means data ok.

	typedef std::atomic<Data> AData;
	static_assert(sizeof(Data) == sizeof(AData));

	AData buf;
};

class AtomicReqRep
{
public:
	typedef int64_t Data;
	typedef std::function<Data(const Data)> Handler;
	bool ClientRequest(const Data request, Data &reply);
	bool ServerProcess(Handler onReq);

private:
	enum State {
		eStateFree,
		eStateRequest,
		eStateReply
	};
	static int GetState(Data d) { return d & MaskBits(3); }
	static Data Encode(Data d, State st) { return (d << 3) | st; }
	static Data Decode(Data d) { return d >> 3; }
	typedef std::chrono::steady_clock steady_clock;
	typedef steady_clock::duration Duration;
	Duration now() { return steady_clock::now().time_since_epoch(); }

	bool DataCas(Data expected, Data val) { return data_.compare_exchange_strong(expected, val); }
	std::atomic<Data> data_;
	std::atomic<Duration> timestamp_;
};

} // namespace robust
#endif // end of include guard: ROBUST_Q31RCWYU