text: // © 2016 and later: Unicode, Inc. and others.
  // License & terms of use: http://www.unicode.org/copyright.html
  /*
   ********************************************************************************
   * Copyright (C) 2003-2013, International Business Machines Corporation
   * and others. All Rights Reserved.
   ******************************************************************************
   *
   * File ISLAMCAL.H
   *
   * Modification History:
   *
   *   Date        Name        Description
   *   10/14/2003  srl         ported from java IslamicCalendar
   *****************************************************************************
   */
  
  #ifndef ISLAMCAL_H
  #define ISLAMCAL_H
  
  #include "unicode/utypes.h"
  
  #if !UCONFIG_NO_FORMATTING
  
  #include "unicode/calendar.h"
  
  U_NAMESPACE_BEGIN
  
  /**
   * <code>IslamicCalendar</code> is a subclass of <code>Calendar</code>
   * that implements the Islamic civil and religious calendars.  It
   * is used as the civil calendar in most of the Arab world and the
   * liturgical calendar of the Islamic faith worldwide.  This calendar
   * is also known as the "Hijri" calendar, since it starts at the time
   * of Mohammed's emigration (or "hijra") to Medinah on Thursday, 
   * July 15, 622 AD (Julian).
   * <p>
   * The Islamic calendar is strictly lunar, and thus an Islamic year of twelve
   * lunar months does not correspond to the solar year used by most other
   * calendar systems, including the Gregorian.  An Islamic year is, on average,
   * about 354 days long, so each successive Islamic year starts about 11 days
   * earlier in the corresponding Gregorian year.
   * <p>
   * Each month of the calendar starts when the new moon's crescent is visible
   * at sunset.  However, in order to keep the time fields in this class
   * synchronized with those of the other calendars and with local clock time,
   * we treat days and months as beginning at midnight,
   * roughly 6 hours after the corresponding sunset.
   * <p>
   * There are two main variants of the Islamic calendar in existence.  The first
   * is the <em>civil</em> calendar, which uses a fixed cycle of alternating 29-
   * and 30-day months, with a leap day added to the last month of 11 out of
   * every 30 years.  This calendar is easily calculated and thus predictable in
   * advance, so it is used as the civil calendar in a number of Arab countries.
   * This is the default behavior of a newly-created <code>IslamicCalendar</code>
   * object.
   * <p>
   * The Islamic <em>religious</em> calendar, however, is based on the <em>observation</em>
   * of the crescent moon.  It is thus affected by the position at which the
   * observations are made, seasonal variations in the time of sunset, the
   * eccentricities of the moon's orbit, and even the weather at the observation
   * site.  This makes it impossible to calculate in advance, and it causes the
   * start of a month in the religious calendar to differ from the civil calendar
   * by up to three days.
   * <p>
   * Using astronomical calculations for the position of the sun and moon, the
   * moon's illumination, and other factors, it is possible to determine the start
   * of a lunar month with a fairly high degree of certainty.  However, these
   * calculations are extremely complicated and thus slow, so most algorithms,
   * including the one used here, are only approximations of the true astronical
   * calculations.  At present, the approximations used in this class are fairly
   * simplistic; they will be improved in later versions of the code.
   * <p>
   * The {@link #setCivil setCivil} method determines
   * which approach is used to determine the start of a month.  By default, the
   * fixed-cycle civil calendar is used.  However, if <code>setCivil(false)</code>
   * is called, an approximation of the true lunar calendar will be used.
   *
   * @see GregorianCalendar
   *
   * @author Laura Werner
   * @author Alan Liu
   * @author Steven R. Loomis
   * @internal
   */
  class U_I18N_API IslamicCalendar : public Calendar {
   public:
    //-------------------------------------------------------------------------
    // Constants...
    //-------------------------------------------------------------------------
    
    /**
     * Calendar type - civil or religious or um alqura
     * @internal 
     */
    enum ECalculationType {
      ASTRONOMICAL,
      CIVIL,
      UMALQURA,
      TBLA
    };
    
    /**
     * Constants for the months
     * @internal
     */
    enum EMonths {
      /**
       * Constant for Muharram, the 1st month of the Islamic year. 
       * @internal
       */
      MUHARRAM = 0,
  
      /**
       * Constant for Safar, the 2nd month of the Islamic year. 
       * @internal
       */
      SAFAR = 1,
  
      /**
       * Constant for Rabi' al-awwal (or Rabi' I), the 3rd month of the Islamic year. 
       * @internal 
       */
      RABI_1 = 2,
  
      /**
       * Constant for Rabi' al-thani or (Rabi' II), the 4th month of the Islamic year. 
       * @internal 
       */
      RABI_2 = 3,
  
      /**
       * Constant for Jumada al-awwal or (Jumada I), the 5th month of the Islamic year. 
       * @internal 
       */
      JUMADA_1 = 4,
  
      /**
       * Constant for Jumada al-thani or (Jumada II), the 6th month of the Islamic year. 
       * @internal 
       */
      JUMADA_2 = 5,
  
      /**
       * Constant for Rajab, the 7th month of the Islamic year. 
       * @internal 
       */
      RAJAB = 6,
  
      /**
       * Constant for Sha'ban, the 8th month of the Islamic year. 
       * @internal 
       */
      SHABAN = 7,
  
      /**
       * Constant for Ramadan, the 9th month of the Islamic year. 
       * @internal 
       */
      RAMADAN = 8,
  
      /**
       * Constant for Shawwal, the 10th month of the Islamic year. 
       * @internal 
       */
      SHAWWAL = 9,
  
      /**
       * Constant for Dhu al-Qi'dah, the 11th month of the Islamic year. 
       * @internal 
       */
      DHU_AL_QIDAH = 10,
  
      /**
       * Constant for Dhu al-Hijjah, the 12th month of the Islamic year. 
       * @internal 
       */
      DHU_AL_HIJJAH = 11,
      
      ISLAMIC_MONTH_MAX
    }; 
  
  
    //-------------------------------------------------------------------------
    // Constructors...
    //-------------------------------------------------------------------------
  
    /**
     * Constructs an IslamicCalendar based on the current time in the default time zone
     * with the given locale.
     *
     * @param aLocale  The given locale.
     * @param success  Indicates the status of IslamicCalendar object construction.
     *                 Returns U_ZERO_ERROR if constructed successfully.
     * @param type     The Islamic calendar calculation type. The default value is CIVIL.
     * @internal
     */
    IslamicCalendar(const Locale& aLocale, UErrorCode &success, ECalculationType type = CIVIL);
  
    /**
     * Copy Constructor
     * @internal
     */
    IslamicCalendar(const IslamicCalendar& other);
  
    /**
     * Destructor.
     * @internal
     */
    virtual ~IslamicCalendar();
  
    /**
     * Sets Islamic calendar calculation type used by this instance.
     *
     * @param type    The calendar calculation type, <code>CIVIL</code> to use the civil
     *                calendar, <code>ASTRONOMICAL</code> to use the astronomical calendar.
     * @internal
     */
    void setCalculationType(ECalculationType type, UErrorCode &status);
      
    /**
     * Returns <code>true</code> if this object is using the fixed-cycle civil
     * calendar, or <code>false</code> if using the religious, astronomical
     * calendar.
     * @internal
     */
    UBool isCivil();
  
  
    // TODO: copy c'tor, etc
  
    // clone
    virtual Calendar* clone() const;
  
   private:
    /**
     * Determine whether a year is a leap year in the Islamic civil calendar
     */
    static UBool civilLeapYear(int32_t year);
      
    /**
     * Return the day # on which the given year starts.  Days are counted
     * from the Hijri epoch, origin 0.
     */
    int32_t yearStart(int32_t year) const;
  
    /**
     * Return the day # on which the given month starts.  Days are counted
     * from the Hijri epoch, origin 0.
     *
     * @param year  The hijri year
     * @param year  The hijri month, 0-based
     */
    int32_t monthStart(int32_t year, int32_t month) const;
      
    /**
     * Find the day number on which a particular month of the true/lunar
     * Islamic calendar starts.
     *
     * @param month The month in question, origin 0 from the Hijri epoch
     *
     * @return The day number on which the given month starts.
     */
    int32_t trueMonthStart(int32_t month) const;
  
    /**
     * Return the "age" of the moon at the given time; this is the difference
     * in ecliptic latitude between the moon and the sun.  This method simply
     * calls CalendarAstronomer.moonAge, converts to degrees, 
     * and adjusts the resultto be in the range [-180, 180].
     *
     * @param time  The time at which the moon's age is desired,
     *              in millis since 1/1/1970.
     */
    static double moonAge(UDate time, UErrorCode &status);
  
    //-------------------------------------------------------------------------
    // Internal data....
    //
      
    /**
     * <code>CIVIL</code> if this object uses the fixed-cycle Islamic civil calendar,
     * and <code>ASTRONOMICAL</code> if it approximates the true religious calendar using
     * astronomical calculations for the time of the new moon.
     */
    ECalculationType cType;
  
    //----------------------------------------------------------------------
    // Calendar framework
    //----------------------------------------------------------------------
   protected:
    /**
     * @internal
     */
    virtual int32_t handleGetLimit(UCalendarDateFields field, ELimitType limitType) const;
    
    /**
     * Return the length (in days) of the given month.
     *
     * @param year  The hijri year
     * @param year  The hijri month, 0-based
     * @internal
     */
    virtual int32_t handleGetMonthLength(int32_t extendedYear, int32_t month) const;
    
    /**
     * Return the number of days in the given Islamic year
     * @internal
     */
    virtual int32_t handleGetYearLength(int32_t extendedYear) const;
      
    //-------------------------------------------------------------------------
    // Functions for converting from field values to milliseconds....
    //-------------------------------------------------------------------------
  
    // Return JD of start of given month/year
    /**
     * @internal
     */
    virtual int32_t handleComputeMonthStart(int32_t eyear, int32_t month, UBool useMonth) const;
  
    //-------------------------------------------------------------------------
    // Functions for converting from milliseconds to field values
    //-------------------------------------------------------------------------
  
    /**
     * @internal
     */
    virtual int32_t handleGetExtendedYear();
  
    /**
     * Override Calendar to compute several fields specific to the Islamic
     * calendar system.  These are:
     *
     * <ul><li>ERA
     * <li>YEAR
     * <li>MONTH
     * <li>DAY_OF_MONTH
     * <li>DAY_OF_YEAR
     * <li>EXTENDED_YEAR</ul>
     * 
     * The DAY_OF_WEEK and DOW_LOCAL fields are already set when this
     * method is called. The getGregorianXxx() methods return Gregorian
     * calendar equivalents for the given Julian day.
     * @internal
     */
    virtual void handleComputeFields(int32_t julianDay, UErrorCode &status);
  
    // UObject stuff
   public: 
    /**
     * @return   The class ID for this object. All objects of a given class have the
     *           same class ID. Objects of other classes have different class IDs.
     * @internal
     */
    virtual UClassID getDynamicClassID(void) const;
  
    /**
     * Return the class ID for this class. This is useful only for comparing to a return
     * value from getDynamicClassID(). For example:
     *
     *      Base* polymorphic_pointer = createPolymorphicObject();
     *      if (polymorphic_pointer->getDynamicClassID() ==
     *          Derived::getStaticClassID()) ...
     *
     * @return   The class ID for all objects of this class.
     * @internal
     */
    /*U_I18N_API*/ static UClassID U_EXPORT2 getStaticClassID(void);
  
    /**
     * return the calendar type, "buddhist".
     *
     * @return calendar type
     * @internal
     */
    virtual const char * getType() const;
  
   private:
    IslamicCalendar(); // default constructor not implemented
  
    // Default century.
   protected:
  
    /**
     * (Overrides Calendar) Return true if the current date for this Calendar is in
     * Daylight Savings Time. Recognizes DST_OFFSET, if it is set.
     *
     * @param status Fill-in parameter which receives the status of this operation.
     * @return   True if the current date for this Calendar is in Daylight Savings Time,
     *           false, otherwise.
     * @internal
     */
    virtual UBool inDaylightTime(UErrorCode& status) const;
  
  
    /**
     * Returns TRUE because the Islamic Calendar does have a default century
     * @internal
     */
    virtual UBool haveDefaultCentury() const;
  
    /**
     * Returns the date of the start of the default century
     * @return start of century - in milliseconds since epoch, 1970
     * @internal
     */
    virtual UDate defaultCenturyStart() const;
  
    /**
     * Returns the year in which the default century begins
     * @internal
     */
    virtual int32_t defaultCenturyStartYear() const;
  
   private:
    /**
     * Initializes the 100-year window that dates with 2-digit years
     * are considered to fall within so that its start date is 80 years
     * before the current time.
     */
    static void U_CALLCONV initializeSystemDefaultCentury(void);
  };
  
  U_NAMESPACE_END
  
  #endif
  #endif
  
  
  
  