// Ring buffer for async I/K-Bus message handling
// Based on muki01/I-K_Bus RingBuffer (MIT license)

#include "RingBuffer.h"
#include <cstring>

RingBuffer::RingBuffer(int size) : _size(size), _head(0), _tail(0) {
    _buf = (byte*)malloc(size);
    if (_buf) {
        memset(_buf, 0, size);
    } else {
        // Allocation failed — disable all operations
        log_e("RingBuffer: malloc(%d) failed", size);
        _size = 0;
    }
}

RingBuffer::~RingBuffer() {
    if (_buf) free(_buf);
}

int RingBuffer::available() {
    return (_size + _head - _tail) % _size;
}

int RingBuffer::capacity() {
    return (_size > 0) ? _size - 1 : 0;
}

int RingBuffer::read() {
    if (_head == _tail) return -1;
    byte c = _buf[_tail];
    _tail = (_tail + 1) % _size;
    return c;
}

byte RingBuffer::write(int c) {
    if (_size == 0) return -1;
    if ((_head + 1) % _size == _tail) return -1;  // full
    _buf[_head] = c;
    _head = (_head + 1) % _size;
    return 0;
}

void RingBuffer::remove(int n) {
    if (_head == _tail) return;
    int avail = available();
    if (n > avail) n = avail;  // clamp to prevent state corruption
    if (n <= 0) return;
    _tail = (_tail + n) % _size;
}

int RingBuffer::peek() {
    if (_head == _tail) return -1;
    return _buf[_tail];
}

int RingBuffer::peek(int n) {
    if (n < 0 || n >= available()) return -1;
    return _buf[(_tail + n) % _size];
}