content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.arrow.driver.jdbc.utils;
  
  import static org.apache.calcite.avatica.util.DateTimeUtils.MILLIS_PER_DAY;
  
  import java.sql.Timestamp;
  import java.time.LocalDate;
  import java.time.LocalDateTime;
  import java.time.LocalTime;
  import java.util.Calendar;
  import java.util.TimeZone;
  import java.util.concurrent.TimeUnit;
  
  /** Datetime utility functions. */
  public class DateTimeUtils {
    private DateTimeUtils() {
      // Prevent instantiation.
    }
  
    /** Subtracts given Calendar's TimeZone offset from epoch milliseconds. */
    public static long applyCalendarOffset(long milliseconds, Calendar calendar) {
      if (calendar == null) {
        calendar = Calendar.getInstance();
      }
  
      final TimeZone tz = calendar.getTimeZone();
      final TimeZone defaultTz = TimeZone.getDefault();
  
      if (tz != defaultTz) {
        milliseconds -= tz.getOffset(milliseconds) - defaultTz.getOffset(milliseconds);
      }
  
      return milliseconds;
    }
  
    /**
     * Converts Epoch millis to a {@link Timestamp} object.
     *
     * @param millisWithCalendar the Timestamp in Epoch millis
     * @return a {@link Timestamp} object representing the given Epoch millis
     */
    public static Timestamp getTimestampValue(long millisWithCalendar) {
      long milliseconds = millisWithCalendar;
      if (milliseconds < 0) {
        // LocalTime#ofNanoDay only accepts positive values
        milliseconds -= ((milliseconds / MILLIS_PER_DAY) - 1) * MILLIS_PER_DAY;
      }
  
      return Timestamp.valueOf(
          LocalDateTime.of(
              LocalDate.ofEpochDay(millisWithCalendar / MILLIS_PER_DAY),
              LocalTime.ofNanoOfDay(TimeUnit.MILLISECONDS.toNanos(milliseconds % MILLIS_PER_DAY))));
    }
  }
  