/*
    * Copyright (C) 2020-2023 Dipl.-Inform. Kai Hofmann. All rights reserved!
    */
   package de.powerstat.validation.values;
   
   
   import java.util.Objects;
   
   import de.powerstat.validation.interfaces.IValueObject;
  
  
  /**
   * Gregorian calendar date.
   *
   * Not DSGVO relevant.
   *
   * TODO next day
   * TODO previous day
   * TODO add x days
   * TODO subtract x days
   * TODO add days, months, years
   * TODO subtract days, months, years
   * TODO getJD
   * TODO getMJD
   * TODO getWeekday
   * TODO date - date = days
   * TODO date - date = days, months, years
   * TODO get WeekNr
   * TODO format date
   * TODO parse date
   * TODO min, max
   */
  public final class GregorianDate implements Comparable<GregorianDate>, IValueObject
   {
    /* *
     * Cache for singletons.
     */
    // private static final Map<NTuple4<GregorianCalendar, Year, Month, Day>, GregorianDate> CACHE = new WeakHashMap<>();
  
    /**
     * Output format.
     */
    private static final String FORMAT_TWODIGIT = "%02d"; //$NON-NLS-1$
  
    /**
     * Year format.
     */
    private static final String FORMAT_FOURDIGIT = "%04d"; //$NON-NLS-1$
  
    /**
     * ISO8601 separator.
     */
    private static final String DATE_SEP = "-"; //$NON-NLS-1$
  
    /**
     * IT - italy constant.
     */
    private static final String IT = "IT"; //$NON-NLS-1$
  
    /**
     * Gregorian calendar.
     */
    private final GregorianCalendar calendar;
  
    /**
     * Year.
     */
    private final Year year;
  
    /**
     * Month.
     */
    private final Month month;
  
    /**
     * Day.
     */
    private final Day day;
  
  
    /**
     * Constructor.
     *
     * @param calendar Gregorian calendar
     * @param year Year
     * @param month Month
     * @param day Day
     */
    private GregorianDate(final GregorianCalendar calendar, final Year year, final Month month, final Day day)
     {
      super();
      Objects.requireNonNull(calendar, "calendar"); //$NON-NLS-1$
      Objects.requireNonNull(year, "year"); //$NON-NLS-1$
      Objects.requireNonNull(month, "month"); //$NON-NLS-1$
      Objects.requireNonNull(day, "day"); //$NON-NLS-1$
      if (day.intValue() > calendar.daysInMonth(year, month)) // TODO Does not work for gregorian reform month
       {
        throw new IllegalArgumentException("Day does not exists in month"); //$NON-NLS-1$
       }
     this.calendar = calendar;
     this.year = year;
     this.month = month;
     this.day = day;
    }
 
 
   /**
    * GregorianDate factory.
    *
    * @param calendar Gregorian calendar
    * @param year Year
    * @param month Month
    * @param day Day
    * @return GregorianDate object
    */
   public static GregorianDate of(final GregorianCalendar calendar, final Year year, final Month month, final Day day)
    {
     /*
     final NTuple4<GregorianCalendar, Year, Month, Day> tuple = NTuple4.of(calendar, year, month, day);
     synchronized (GregorianDate.class)
      {
       GregorianDate obj = GregorianDate.CACHE.get(tuple);
       if (obj != null)
        {
         return obj;
        }
       obj = new GregorianDate(calendar, year, month, day);
       GregorianDate.CACHE.put(tuple, obj);
       return obj;
      }
     */
     return new GregorianDate(calendar, year, month, day);
    }
 
 
   /**
    * GregorianDate factory for country=IT.
    *
    * @param year Year
    * @param month Month
    * @param day Day
    * @return GregorianDate object
    */
   public static GregorianDate of(final Year year, final Month month, final Day day)
    {
     return GregorianDate.of(GregorianCalendar.of(Country.of(IT)), year, month, day);
    }
 
 
   /**
    * GregorianDate factory for country=IT.
    *
    * @param value String value of ISO8601 type yyyy-mm-dd
    * @return GregorianDate object
    */
   public static GregorianDate of(final String value)
    {
     final String[] values = value.split(DATE_SEP);
     if (values.length != 3)
      {
       throw new IllegalArgumentException("Format not as expected: yyyy-mm-dd");
      }
     return GregorianDate.of(GregorianCalendar.of(Country.of(IT)), Year.of(values[0]), Month.of(values[1]), Day.of(values[2]));
    }
 
 
   /**
    * Returns the value of this GregorianDate as a string.
    *
    * @return The text value represented by this object after conversion to type string in ISO8601 format with - as separator.
    */
   @Override
   public String stringValue()
    {
     return String.format(GregorianDate.FORMAT_FOURDIGIT, this.year.longValue()) + GregorianDate.DATE_SEP + String.format(GregorianDate.FORMAT_TWODIGIT, this.month.intValue()) + GregorianDate.DATE_SEP + String.format(GregorianDate.FORMAT_TWODIGIT, this.day.intValue());
    }
 
 
   /**
    * Calculate hash code.
    *
    * @return Hash
    * @see java.lang.Object#hashCode()
    */
   @Override
   public int hashCode()
    {
     // TODO calendar
     return Objects.hash(this.year, this.month, this.day);
    }
 
 
   /**
    * Is equal with another object.
    *
    * @param obj Object
    * @return true when equal, false otherwise
    * @see java.lang.Object#equals(java.lang.Object)
    */
   @Override
   public boolean equals(final Object obj)
    {
     if (this == obj)
      {
       return true;
      }
     if (!(obj instanceof GregorianDate))
      {
       return false;
      }
     final GregorianDate other = (GregorianDate)obj;
     // TODO calendar
     boolean result = this.year.equals(other.year);
     if (result)
      {
       result = this.month.equals(other.month);
       if (result)
        {
         result = this.day.equals(other.day);
        }
      }
     return result;
    }
 
 
   /**
    * Returns the string representation of this GregorianDate.
    *
    * The exact details of this representation are unspecified and subject to change, but the following may be regarded as typical:
    *
    * "GregorianDate[country=IT, date=2020-07-06]"
    *
    * @return String representation of this GregorianDate
    * @see java.lang.Object#toString()
    */
   @Override
   public String toString()
    {
     final var builder = new StringBuilder(30);
     builder.append("GregorianDate[country=").append(this.calendar.getCountry().stringValue()).append(", date=").append(stringValue()).append(']'); //$NON-NLS-1$ //$NON-NLS-2$
     return builder.toString();
    }
 
 
   /**
    * Compare with another object.
    *
    * @param obj Object to compare with
    * @return 0: equal; 1: greater; -1: smaller
    * @see java.lang.Comparable#compareTo(java.lang.Object)
    */
   @Override
   public int compareTo(final GregorianDate obj)
    {
     Objects.requireNonNull(obj, "obj"); //$NON-NLS-1$
     // TODO calendar
     int result = this.year.compareTo(obj.year);
     if (result == 0)
      {
       result = this.month.compareTo(obj.month);
       if (result == 0)
        {
         result = this.day.compareTo(obj.day);
        }
      }
     return result;
    }
 
 
   /**
    * Calculate easter date for year.
    *
    * @param calendar Gregorian calendar
    * @param year Year
    * @return GregorianDate of easter for given year
    */
   @SuppressWarnings("PMD.ShortVariable")
   public static GregorianDate easter(final GregorianCalendar calendar, final Year year)
    {
     final long a = year.longValue() % 19;
     final long b = year.longValue() / 100;
     final long c = year.longValue() % 100;
     final long d = ((((19 * a) + b) - (b / 4) - (((b - ((b + 8) / 25)) + 1) / 3)) + 15) % 30;
     final long e = ((32 + (2 * (b % 4)) + (2 * (c / 4))) - d - (c % 4)) % 7;
     final long f = ((d + e) - (7 * ((a + (11 * d) + (22 * e)) / 451))) + 114;
     final var day = Day.of(((int)f % 31) + 1);
     final var month = Month.of((int)(f / 31));
     return GregorianDate.of(calendar, year, month, day);
    }
 
  }