#include "utils.h"

int ring_buffer_read(struct ring_buffer* rb, char* dest, int size) {
  int slice1 = size;
  int slice2 = 0;

  int used_space = ring_buffer_used_space (rb);
  if (used_space < slice1)
    slice1 = used_space;

  if (RING_BUFFER_SIZE - rb->head < slice1) {
    slice1 = RING_BUFFER_SIZE - rb->head;
    slice2 = size - slice1;
    if (used_space - slice1 < slice2)
      slice2 = used_space - slice1;
  }

  printf("max_buffer=%d, head=%d, tail=%d, size=%d, slice1=%d, slice2=%d\n", RING_BUFFER_SIZE, rb->head, rb->tail, size, slice1, slice2);
  memcpy(dest, rb->buffer + rb->head, slice1);
  memcpy(dest+slice1, rb->buffer, slice2);

  return slice1 + slice2;
}

void ring_buffer_ack_read(struct ring_buffer* rb, int size) {
  if (size > ring_buffer_used_space (rb)) {
    fprintf(stderr, "You try to ack more data than contained in the ring buffer\n");
    exit(EXIT_FAILURE);
  }
  rb->head = (rb->head + size) % RING_BUFFER_SIZE;
}

int ring_buffer_write(struct ring_buffer* rb, char* source, int size) {
  if (size > ring_buffer_free_space (rb)) {
    fprintf(stderr, "You try to write more data than available space in the buffer\n");
    exit(EXIT_FAILURE);
  }

  int slice1 = size;
  int slice2 = 0;

  if (RING_BUFFER_SIZE - rb->tail < slice1) {
    slice1 = RING_BUFFER_SIZE - rb->tail;
    slice2 = size - slice1;
  }

  memcpy(rb->buffer + rb->tail, source, slice1);
  memcpy(rb->buffer, source + slice1, slice2);

  rb->tail = (rb->tail + slice1 + slice2) % RING_BUFFER_SIZE;

  return slice1 + slice2;
}

int ring_buffer_free_space(struct ring_buffer* rb) {
  if (rb->head > rb->tail) return rb->head - rb->tail;
  return RING_BUFFER_SIZE - (rb->tail - rb->head);
}

int ring_buffer_used_space(struct ring_buffer* rb) {
  return RING_BUFFER_SIZE - ring_buffer_free_space (rb);
}