#include <stdint.h>
#include <stdbool.h>
#include <stdatomic.h>

#ifndef QUEUE_H
#define QUEUE_H

typedef struct {
  uint16_t element_size;
  uint16_t length;

  atomic_uint_least16_t curr_read_ptr;
  atomic_uint_least16_t curr_write_ptr;
  atomic_uint_least16_t space;

  uint8_t elements[0];
} queue_t;

/**
 * @brief Allocate needed memory for given element size and total length of the fifo.
 * @param[in] element_size The size of one element.
 * @param[in] length The maximum number of elements
 * @return The malloced memory, not initialized. Call @see queue_init on this.
 */
queue_t* queue_malloc(uint16_t element_size, uint16_t length);

/**
 * @brief Initialize queue, given allocated memory
 * @details To allocate  the memory, @see queue_malloc might be used.
 * @param[in,out] queue The queue to initialize
 * @param[in] element_size The size of one element.
 * @param[in] length The maximum number of elements.
 */
void queue_init(queue_t* queue, uint16_t element_size, uint16_t length);

/**
 * @brief Enqueue the given element to the queue.
 * @param[in,out] queue The queue to enqueue the element to.
 * @param[out] element The element to enqueue, its size should be element_size used in @see queue_init. If it isn't, wrong part of memory might be read.
 * @return Whether the element was enqueued. If false, queue is full.
 */
bool queue_enqueue(queue_t* queue, void* element);

/**
 * @brief Dequeue the first element.
 * @details The element at beginning of queue is returned, and the pointer is incremented
 * so that the element is no longer valid and there is space for a new one. This implementation
 * is not thread safe! The element might get overwritten.
 * @param[in,out] queue The queue to dequeue from.
 * @return The element.
 */
void* queue_dequeue(queue_t* queue);

/**
 * @brief Dequeue the first element.
 * @details The element at beginning of queue is returned, and the pointer is incremented.
 * @param[in,out] queue The queue to dequeue from.
 * @param[out] element Space for the element to write it to.
 * @return If there was an element to read.
 */
bool queue_dequeue_safely(queue_t* queue, void* element);

/**
 * @brief Show the first element.
 * @details The element at beginning of queue is returned,
 * @param[in,out] queue The queue to peek to.
 * @return The element.
 */
void* queue_peek(queue_t* queue);

/**
 * @brief Get number of elements in the queue
 * @param[in,out] queue The queue.
 * @return Number of elements in the queue.
 */
uint16_t queue_count(queue_t* queue);

uint16_t queue_space(queue_t* queue);

#endif // QUEUE_H