waituntil/src/main/java/de/jotoho/waituntil/TimeCalculator.java

package de.jotoho.waituntil;

/*
    waituntil - a tool for delaying command execution until the specified time
    Copyright (C) 2022 Jonas Tobias Hopusch

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalTime;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.FormatStyle;
import java.util.TimeZone;

import static java.lang.System.Logger.Level;

public final class TimeCalculator {

    public static ZonedDateTime calculateAndAnnounceTargetTime(final String userTimeInputRaw) {
        final var userTimeInputRelative = LocalTime.parse(userTimeInputRaw);
        final var userTimeInputAbsolute = ZonedDateTime.of(LocalDate.now(),
                                                           userTimeInputRelative,
                                                           TimeZone.getDefault()
                                                                   .toZoneId());

        final var userTimeInputFinal = (Instant.now()
                                               .isBefore(userTimeInputAbsolute.toInstant()))
                                       ? userTimeInputAbsolute
                                       : userTimeInputAbsolute.plusDays(1);

        final var formattedTimeStamp =
            userTimeInputFinal.format(DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG));

        final String msg = switch (GlobalConf.applicationOutputLanguage) {
            case GlobalConf.langGerman -> ("Dieses Program wird bis zum %s warten.").formatted(
                formattedTimeStamp);
            default -> "WaitUntil will suspend until %s".formatted(formattedTimeStamp);
        };
        System.getLogger("timecalculator")
              .log(Level.INFO, msg);

        return userTimeInputFinal;
    }
}