/* @tier easy @module mm @transform master-util */
/*
 * mm_cu_0003.c - 마스터 공통 유틸리티 (plain C)  [tier=easy]
 */
#include "mm_cu_0003.h"

#include <string.h>

/* 일할 정산: rate_bp 를 경과일(1..10000) 비율로 안분한다 */
long mm_cu_0003_fee(long amount, int rate_bp)
{
    long days, prorated;
    if (amount <= 0 || rate_bp < 0)
        return 0;
    days = (long)rate_bp;
    if (days > 10000L)
        days = 10000L;
    prorated = (amount * days) / 10000L;
    return prorated;
}

/* 반올림(절대값 0.5 기준 올림, 부호 보존)으로 unit 정규화 */
long mm_cu_0003_round_unit(long amount, long unit)
{
    long a, q, r, res;
    int neg;
    if (unit <= 0)
        return amount;
    neg = amount < 0;
    a = neg ? -amount : amount;
    q = a / unit;
    r = a - q * unit;
    if (r * 2 >= unit)
        q += 1;
    res = q * unit;
    return neg ? -res : res;
}

/* 디지털 루트(반복 자릿수합)로 분류 */
int mm_cu_0003_classify(long amount)
{
    long v = amount < 0 ? -amount : amount;
    int root;
    if (v == 0)
        return 0;
    root = (int)(1 + (v - 1) % 9);
    if (root <= 3) return 0;
    if (root <= 6) return 1;
    return 2;
}