#include <stddef.h>

int replace_char_line(char *buf, int key, int *replacements_left) {
    (void)key;
    int replaced = 0;
    int count = 0;

    for (size_t i = 0; buf[i] != '\0'; i++) {
        if (buf[i] == '\n') continue;
        count++;
        if (count % 3 == 0 && *replacements_left > 0) {
            buf[i] = ' ';
            replaced++;
            (*replacements_left)--;
            if (*replacements_left == 0) break;
        }
    }
    return replaced;
}