package edu.rice.rubis.servlets;

import java.util.GregorianCalendar;

/** This class provides additionnal functions that the GregorianCalendar
 * class does not provide. It is mainly to compute time differences and
 * display the date in a database understandable format.
 */

public class TimeManagement
{

  public TimeManagement()
  {
  }

  /** Returns a string representation of the current date (when the method is called)
   * conforming to the following database format : 'YYYY-MM-DD hh:mm:ss'
   *
   * @return current date in database format
   *
   */
  public static String currentDateToString()
  {
    GregorianCalendar d = new GregorianCalendar();
    return dateToString(d);
  }

  /** Returns a string representation of a date conforming to 
   * the following database format : 'YYYY-MM-DD hh:mm:ss'
   *
   * @return current date in database format
   *
   */
  public static String dateToString(GregorianCalendar d)
  {
    String result;
    int year, month, day, hour, minute, second;

    year = d.get(d.YEAR);
    month = d.get(d.MONTH) + 1;
    day = d.get(d.DATE);
    hour = d.get(d.HOUR_OF_DAY);
    minute = d.get(d.MINUTE);
    second = d.get(d.SECOND);
    result =
      year + "-" + month + "-" + day + " " + hour + ":" + minute + ":" + second;
    return result;
  }

  /** Returns a string representation of the time elapsed between startDate
   * and endDate. Example of a returned string : "1 month 3 days 6 hours 33 minutes 4 seconds 234 milliseconds"
   *
   * @param startDate beginning date
   * @param endDate ending date
   *
   * @return string containing the time difference up to the millisecond
   *
   */
  public static String diffTime(
    GregorianCalendar startDate,
    GregorianCalendar endDate)
  {
    int year, month, day, hour, minute, second, millis;
    String result = "";

    year = endDate.get(endDate.YEAR) - startDate.get(startDate.YEAR);
    month = endDate.get(endDate.MONTH) - startDate.get(startDate.MONTH);
    day = endDate.get(endDate.DATE) - startDate.get(startDate.DATE);
    hour =
      endDate.get(endDate.HOUR_OF_DAY) - startDate.get(startDate.HOUR_OF_DAY);
    minute = endDate.get(endDate.MINUTE) - startDate.get(startDate.MINUTE);
    second = endDate.get(endDate.SECOND) - startDate.get(startDate.SECOND);
    millis =
      endDate.get(endDate.MILLISECOND) - startDate.get(startDate.MILLISECOND);

    if (millis < 0)
    {
      millis = millis + 1000;
      second = second - 1;
    }
    if (second < 0)
    {
      second = second + 60;
      minute = minute - 1;
    }
    if (minute < 0)
    {
      minute = minute + 60;
      hour = hour - 1;
    }
    if (hour < 0)
    {
      hour = hour + 24;
      day = day - 1;
    }
    if (day < 0)
    {
      day = day + startDate.getActualMaximum(startDate.DAY_OF_MONTH);
      // is the same as startDate.DATE
      month = month - 1;
    }
    if (month < 0)
    {
      month = month + 12;
      year = year - 1;
    }

    if (year > 0)
      result = year + " year";
    if (year > 1)
      result = result + "s ";
    else
      result = result + " ";
    if (month > 0)
      result = result + month + " month";
    if (month > 1)
      result = result + "s ";
    else
      result = result + " ";
    if (day > 0)
      result = result + day + " day";
    if (day > 1)
      result = result + "s ";
    else
      result = result + " ";
    if (hour > 0)
      result = result + hour + " hour";
    if (hour > 1)
      result = result + "s ";
    else
      result = result + " ";
    if (minute > 0)
      result = result + minute + " minute";
    if (minute > 1)
      result = result + "s ";
    else
      result = result + " ";
    if (second > 0)
      result = result + second + " second";
    if (second > 1)
      result = result + "s ";
    else
      result = result + " ";
    result = result + millis + " millisecond";
    if (millis > 1)
      result = result + "s ";
    else
      result = result + " ";
    return result;
  }

  /** Compute a new GregorianCalendar from a beginning date and a duration in days.
   *
   * @param startDate beginning date
   * @param durationInDays number of days to add to startDate.
   *
   * @return date corresponding to startDate+durationInDays
   *
   */
  public static GregorianCalendar addDays(
    GregorianCalendar startDate,
    int durationInDays)
  {
    GregorianCalendar date = (GregorianCalendar) startDate.clone();
    date.add(date.DATE, durationInDays);
    return date;
  }
}