/*
    *  Copyright 2001-2005 Stephen Colebourne
    *
    *  Licensed 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.joda.time.chrono.gj;
  
  import org.joda.time.DateTimeField;
  
  /**
   * A reference Julian chronology implementation, intended for testing purposes
   * only. Correctness is favored over performance. The key functions for date
   * calculations are based on ones provided in "Calendrical Calculations", ISBN
   * 0-521-77752-6.
   *
   * @author Brian S O'Neill
   */
  public final class TestJulianChronology extends TestGJChronology {
  
      private static final long JULIAN_EPOCH;
  
      static {
          // Constant as defined in book.
          JULIAN_EPOCH = new TestGregorianChronology().fixedFromGJ(0, 12, 30);
      }
  
      /**
       * Constructs with an epoch of 1969-12-19.
       */
      public TestJulianChronology() {
          super(1969, 12, 19);
      }
  
      public TestJulianChronology(int epochYear, int epochMonth, int epochDay) {
          super(epochYear, epochMonth, epochDay);
      }
  
      public DateTimeField dayOfMonth() {
          return new TestJulianDayOfMonthField(this); 
      }
  
      public DateTimeField weekyear() {
          return new TestJulianWeekyearField(this);
      }
  
      public DateTimeField monthOfYear() {
          return new TestJulianMonthOfYearField(this);
      }
  
      public DateTimeField year() {
          return new TestJulianYearField(this);
      }
  
      public String toString() {
          return "TestJulianChronology";
      }
  
      long millisPerYear() {
          return (long)(365.25 * MILLIS_PER_DAY);
      }
  
      long millisPerMonth() {
          return (long)(365.25 * MILLIS_PER_DAY / 12);
      }
  
      boolean isLeapYear(int year) {
          if (year == 0) {
              throw new IllegalArgumentException("Illegal year: " + year);
          }
          return mod(year, 4) == (year > 0 ? 0 : 3);
      }
  
      /**
       * @return days from 0001-01-01
       */
      long fixedFromGJ(int year, int monthOfYear, int dayOfMonth) {
          if (year == 0) {
              throw new IllegalArgumentException("Illegal year: " + year);
          }
          int y = (year < 0) ? year + 1 : year;
          long y_m1 = y - 1;
          long f = JULIAN_EPOCH - 1 + 365 * y_m1 + div(y_m1, 4)
              + div(367 * monthOfYear - 362, 12) + dayOfMonth;
          if (monthOfYear > 2) {
              f += isLeapYear(year) ? -1 : -2;
          }
          return f;
      }
  
     /**
      * @param date days from 0001-01-01
      * @return gj year
      */
     int gjYearFromFixed(long date) {
         return gjFromFixed(date)[0];
     }
 
     /**
      * @param date days from 0001-01-01
      * @return gj year, monthOfYear, dayOfMonth
      */
     int[] gjFromFixed(long date) {
         long approx = div(4 * (date - JULIAN_EPOCH) + 1464, 1461);
         long year = (approx <= 0) ? approx - 1 : approx;
         int year_i = (int)year;
         if (year_i != year) {
             throw new RuntimeException("year cannot be cast to an int: " + year);
         }
         long priorDays = date - fixedFromGJ(year_i, 1, 1);
         long correction;
         if (date < fixedFromGJ(year_i, 3, 1)) {
             correction = 0;
         } else if (isLeapYear(year_i)) {
             correction = 1;
         } else {
             correction = 2;
         }
         int monthOfYear = (int)div(12 * (priorDays + correction) + 373, 367);
         int day = (int)(date - fixedFromGJ(year_i, monthOfYear, 1) + 1);
 
         return new int[]{year_i, monthOfYear, day};
     }
 
     long fixedFromISO(int weekyear, int weekOfWeekyear, int dayOfWeek) {
         if (weekyear == 0) {
             throw new IllegalArgumentException("Illegal weekyear: " + weekyear);
         }
         if (weekyear == 1) {
             weekyear = -1;
         } else {
             weekyear--;
         }
         return nthWeekday(weekOfWeekyear, 0, weekyear, 12, 28) + dayOfWeek;
     }
 
     /**
      * @param date days from 0001-01-01
      * @return iso weekyear, weekOfWeekyear, dayOfWeek (1=Monday to 7)
      */
     int[] isoFromFixed(long date) {
         int weekyear = gjYearFromFixed(date - 3);
         int nextWeekyear;
         if (weekyear == -1) {
             nextWeekyear = 1;
         } else {
             nextWeekyear = weekyear + 1;
         }
         if (date >= fixedFromISO(nextWeekyear, 1, 1)) {
             weekyear = nextWeekyear;
         }
         int weekOfWeekyear = (int)(div(date - fixedFromISO(weekyear, 1, 1), 7) + 1);
         int dayOfWeek = (int)amod(date, 7);
         return new int[]{weekyear, weekOfWeekyear, dayOfWeek};
     }
 }