/*
 * =====================================================================================
 *
 *       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 "log.h"
#include <atomic>
#include <chrono>
#include <memory>
#include <mutex>
#include <string>
#include <sys/file.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

namespace robust
{

using namespace std::chrono;
using namespace std::chrono_literals;
constexpr uint64_t MaskBits(int nbits) { return (uint64_t(1) << nbits) - 1; }

void QuickSleep();

class CasMutex
{
	typedef uint64_t locker_t;
	static inline locker_t this_locker() { return pthread_self(); }
	static const uint64_t kLockerMask = MaskBits(63);

public:
	CasMutex() :
	    meta_(0) {}
	int try_lock()
	{
		auto old = meta_.load();
		int r = 0;
		if (!Locked(old)) {
			r = MetaCas(old, Meta(1, this_locker()));
		}
		return r;
	}
	int lock()
	{
		int r = 0;
		do {
			r = try_lock();
		} while (r == 0);
		return r;
	}
	void unlock()
	{
		auto old = meta_.load();
		if (Locked(old) && Locker(old) == this_locker()) {
			MetaCas(old, Meta(0, this_locker()));
		}
	}

private:
	std::atomic<uint64_t> meta_;
	bool Locked(uint64_t meta) { return (meta >> 63) == 1; }
	locker_t Locker(uint64_t meta) { return meta & kLockerMask; }
	uint64_t Meta(uint64_t lk, locker_t lid) { return (lk << 63) | lid; }
	bool MetaCas(uint64_t exp, uint64_t val) { return meta_.compare_exchange_strong(exp, val); }
};

class NullMutex
{
public:
	template <class... T>
	explicit NullMutex(T &&...t) {} // easy test.
	bool try_lock() { return true; }
	void lock() {}
	void unlock() {}
};

// flock + mutex
class FMutex
{
public:
	typedef uint64_t id_t;
	FMutex(id_t id) :
	    id_(id), fd_(Open(id_))
	{
		if (fd_ == -1) { throw "error create mutex!"; }
	}
	~FMutex() { Close(fd_); }
	bool try_lock();
	void lock();
	void unlock();

private:
	static std::string GetPath(id_t id)
	{
		const std::string dir("/tmp/.bhome_mtx");
		mkdir(dir.c_str(), 0777);
		return dir + "/fm_" + std::to_string(id);
	}
	static int Open(id_t id) { return open(GetPath(id).c_str(), O_CREAT | O_RDONLY, 0666); }
	static int Close(int fd) { return close(fd); }
	void FLock();
	void FUnlock();
	id_t id_;
	int fd_;
	std::mutex mtx_;
};

union semun {
	int val;               /* Value for SETVAL */
	struct semid_ds *buf;  /* Buffer for IPC_STAT, IPC_SET */
	unsigned short *array; /* Array for GETALL, SETALL */
	struct seminfo *__buf; /* Buffer for IPC_INFO
                                           (Linux-specific) */
};

class SemMutex
{
public:
	SemMutex(key_t key) :
	    key_(key), sem_id_(semget(key, 1, 0666))
	{
		if (sem_id_ == -1) { throw "error create semaphore."; }
	}
	~SemMutex() {}

	bool try_lock()
	{
		sembuf op = {0, -1, SEM_UNDO | IPC_NOWAIT};
		return semop(sem_id_, &op, 1) == 0;
	}

	void lock()
	{
		sembuf op = {0, -1, SEM_UNDO};
		semop(sem_id_, &op, 1);
	}

	void unlock()
	{
		sembuf op = {0, 1, SEM_UNDO};
		semop(sem_id_, &op, 1);
	}

private:
	key_t key_;
	int sem_id_;
};

template <class Lock>
class Guard
{
public:
	Guard(Lock &l) :
	    l_(l) { l_.lock(); }
	~Guard() { l_.unlock(); }

private:
	Guard(const Guard &);
	Guard(Guard &&);
	Lock &l_;
};

template <class D, class Alloc = std::allocator<D>>
class CircularBuffer
{
	typedef uint32_t size_type;
	typedef uint32_t count_type;
	typedef uint64_t meta_type;
	static size_type Pos(meta_type meta) { return meta & 0xFFFFFFFF; }
	static count_type Count(meta_type meta) { return meta >> 32; }
	static meta_type Meta(meta_type count, size_type pos) { return (count << 32) | pos; }

public:
	typedef D Data;

	CircularBuffer(const size_type cap) :
	    CircularBuffer(cap, Alloc()) {}
	CircularBuffer(const size_type cap, Alloc const &al) :
	    capacity_(cap + 1), mhead_(0), mtail_(0), al_(al), buf(al_.allocate(capacity_))
	{
		if (!buf) {
			throw("robust CircularBuffer allocate error: alloc buffer failed, out of mem!");
		} else {
			memset(&buf[0], 0, sizeof(D) * capacity_);
		}
	}
	~CircularBuffer() { al_.deallocate(buf, capacity_); }

	bool push_back(const Data d)
	{
		auto old = mtail();
		auto pos = Pos(old);
		auto full = ((capacity_ + pos + 1 - head()) % capacity_ == 0);
		if (!full) {
			buf[pos] = d;
			return mtail_.compare_exchange_strong(old, next(old));
		}
		return false;
	}
	bool pop_front(Data &d)
	{
		auto old = mhead();
		auto pos = Pos(old);
		if (!(pos == tail())) {
			d = buf[pos];
			return mhead_.compare_exchange_strong(old, next(old));
		} else {
			return false;
		}
	}

private:
	CircularBuffer(const CircularBuffer &);
	CircularBuffer(CircularBuffer &&);
	CircularBuffer &operator=(const CircularBuffer &) = delete;
	CircularBuffer &operator=(CircularBuffer &&) = delete;

	meta_type next(meta_type meta) const { return Meta(Count(meta) + 1, (Pos(meta) + 1) % capacity_); }
	size_type head() const { return Pos(mhead()); }
	size_type tail() const { return Pos(mtail()); }
	meta_type mhead() const { return mhead_.load(); }
	meta_type mtail() const { return mtail_.load(); }
	// data
	const size_type capacity_;
	std::atomic<meta_type> mhead_;
	std::atomic<meta_type> mtail_;
	Alloc al_;
	typename Alloc::pointer buf = nullptr;
};

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 like_empty() const { return head() == tail() && Empty(buf[head()]); }
	bool like_full() const { return head() == tail() && !Empty(buf[head()]); }
	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];
};

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