#include "ring_buffer.h"

#include <stdlib.h>
#include <stdint.h>
#include <string.h>

/*
 * Type definitions
 */
typedef struct {
    char *buffer;
    uint32_t head;
    uint32_t tail;
    uint32_t size;
} ring_buffer_t;

/*
 * Public API
 */
rb_handle_t rb_allocate(uint32_t size) {
    ring_buffer_t *rb = calloc(1, sizeof(ring_buffer_t));
    if (!rb) {
        return NULL;
    }
    rb->buffer = malloc(size);
    if (!rb->buffer) {
        free(rb);
        rb = NULL;
    }
    rb->size = size;
    return rb;
}

void rb_free(rb_handle_t _rb) {
    if (!_rb) {
        return;
    }
    ring_buffer_t *rb = _rb;
    free(rb->buffer);
    free(rb);
}

uint32_t rb_get_free_bytes(rb_handle_t _rb) {
    ring_buffer_t *rb = _rb;
    if (rb->head == rb->tail) {
        return rb->size - 1;
    }
    if (rb->head < rb->tail) {
        return rb->tail - rb->head - 1;
    }
    return rb->size - (rb->head - rb->tail) - 1;
}

uint32_t rb_raw_read_size(rb_handle_t _rb) {
    ring_buffer_t *rb = _rb;
    if (rb->head == rb->tail) {
        return 0;
    }
    if (rb->head < rb->tail) {
        return rb->size - rb->tail;
    }
    return rb->head - rb->tail;
}

const void *rb_raw_read_ptr(rb_handle_t _rb) {
    ring_buffer_t *rb = _rb;
    return rb->buffer + rb->tail;
}

uint32_t rb_raw_read_advance(rb_handle_t _rb, uint32_t size) {
    if (size) {
        ring_buffer_t *rb = _rb;
        rb->tail += size;
        rb->tail %= rb->size;
    }
    return rb_raw_read_size(_rb);
}

uint32_t rb_raw_write_size(rb_handle_t _rb) {
    ring_buffer_t *rb = _rb;
    if (rb->head < rb->tail) {
        return rb->tail - rb->head -1;
    }
    return rb->size - rb->head;
}

void *rb_raw_write_ptr(rb_handle_t _rb) {
    ring_buffer_t *rb = _rb;
    return rb->buffer + rb->head;
}

uint32_t rb_raw_write_advance(rb_handle_t _rb, uint32_t size) {
    if (size) {
        ring_buffer_t *rb = _rb;
        rb->head += size;
        rb->head %= rb->size;
    }
    return rb_raw_write_size(_rb);
}