#include "temperature.h"
#include <stdio.h>
int format_reading(const Reading *in, char *buf, size_t len) {
    if (!in || !buf || len < 16) return 1;
    int n = snprintf(buf, len, "{\"sensor\":\"%s\",\"celsius\":%.2f}", in->sensor, in->celsius);
    return (n < 0 || (size_t)n >= len) ? 2 : 0;
}