#pragma once
#include <array>
#include <atomic>
#include <cassert>
#include <format>
#include <iostream>
#include <limits>
#include <thread>
namespace lfq {

template <typename T, size_t Size = 256>
class LockFreeQueue {
  static_assert(!(Size & (Size - 1)), "Size must be power of two");

  struct node {
    node() = default;
    node(size_t pos, T obj) : pos(pos), obj(obj) {}
    node(node& oth) : pos(oth.pos.load()), obj(oth.obj) {}
    node(node&& oth) : pos(oth.pos.load()), obj(std::move(oth.obj)) {}
    node& operator=(node& oth) {
      pos = oth.pos.load();
      obj = oth.obj;
      return *this;
    }
    node& operator=(node&& oth) {
      pos = oth.pos.load();
      obj = std::move(oth.obj);
      return *this;
    }

    std::atomic<size_t> pos{std::numeric_limits<size_t>::max()};
    T obj;
  };

 public:
  LockFreeQueue() : enqueue_pos(0), dequeue_pos(0) {}

  void push_back(const T& element);
  void pull_front(T& element);
  size_t apprx_available() const;
  bool is_full() const;
  bool is_empty() const;

 private:
  static constexpr size_t mask{Size - 1};
  std::atomic<size_t> enqueue_pos;
  std::atomic<size_t> dequeue_pos;
  std::array<node, Size> elements;
};

/**
 * @brief lfq implementation of pull operation.
 * result will be written to reference argument
 * it will block the thread until success
 */
template <typename T, size_t Size>
void LockFreeQueue<T, Size>::pull_front(T& element) {
  node* n_obj;
  size_t fix_pos{0};
  bool res{false};
  while (!res) {
    while (is_empty()) {
      std::this_thread::yield();
    }
    fix_pos = dequeue_pos.load();
    n_obj = &elements[fix_pos & mask];
    if (n_obj->pos != fix_pos) {
      // someone installed the value already retry
      std::this_thread::yield();
      continue;
    }
    res = dequeue_pos.compare_exchange_weak(fix_pos, fix_pos + 1);
  }
  element = n_obj->obj;
  n_obj->pos = std::numeric_limits<size_t>::max();
}

/**
 * @brief lock free implementation for push back operation
 * @details trying my best to make it work :D
 */
template <typename T, size_t Size>
void LockFreeQueue<T, Size>::push_back(const T& element) {
  size_t fix_pos{0};
  bool res{false};
  node obj;
  while (!res) {
    while (is_full()) {
      std::this_thread::yield();
    }
    fix_pos = enqueue_pos.load();
    obj = elements[fix_pos & mask];
    res = enqueue_pos.compare_exchange_weak(fix_pos, fix_pos + 1);
  }
  elements[fix_pos & mask] = node{fix_pos, element};
}

template <typename T, size_t Size>
bool LockFreeQueue<T, Size>::is_full() const {
  assert(enqueue_pos.load() >= dequeue_pos.load());
  return enqueue_pos.load() - dequeue_pos.load() >= Size;
}

template <typename T, size_t Size>
bool LockFreeQueue<T, Size>::is_empty() const {
  return enqueue_pos.load() == dequeue_pos.load();
}

template <typename T, size_t Size>
size_t LockFreeQueue<T, Size>::apprx_available() const {
  assert(enqueue_pos.load() >= dequeue_pos.load());
  return enqueue_pos.load() - dequeue_pos.load();
}

}  // namespace lfq