module pind.samples.ja.assert_.assert_2;

import std.stdio;
import std.string;
import std.exception;

/* メッセージを表示した後、
 * 時刻を時と分として読み込む。 */
void readTime(string message,
              out int hour,
              out int minute) {
    write(message, "? (HH:MM) ");

    readf(" %s:%s", &hour, &minute);

    enforce((hour >= 0) && (hour <= 23) &&
            (minute >= 0) && (minute <= 59),
            "Invalid time!");
}

/* 時刻を文字列形式で返す。 */
string timeToString(int hour, int minute) {
    assert((hour >= 0) && (hour <= 23));
    assert((minute >= 0) && (minute <= 59));

    return format("%02s:%02s", hour, minute);
}

/* 開始時刻に継続時間を加算し、
 * その結果を3番目のパラメータのペアとして返す。 */
void addDuration(int startHour, int startMinute,
                 int durationHour, int durationMinute,
                 out int resultHour, out int resultMinute) {
    resultHour = startHour + durationHour;
    resultMinute = startMinute + durationMinute;

    if (resultMinute > 59) {
        ++resultHour;
    }
}

void main() {
    int startHour;
    int startMinute;
    readTime("Start time", startMinute, startHour);

    int durationHour;
    int durationMinute;
    readTime("Duration", durationHour, durationMinute);

    int endHour;
    int endMinute;
    addDuration(startHour, startMinute,
                durationHour, durationMinute,
                endHour, endMinute);

    writefln("%s hours and %s minutes after %s is %s.",
             durationHour, durationMinute,
             timeToString(startHour, startMinute),
             timeToString(endHour, endMinute));
}