/*
    *  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;
  
  import java.io.Serializable;
  
  /**
   * Identifies a field, such as year or minuteOfHour, in a chronology-neutral way.
   * <p>
   * A field type defines the type of the field, such as hourOfDay.
   * If does not directly enable any calculations, however it does provide a
   * {@link #getField(Chronology)} method that returns the actual calculation engine
   * for a particular chronology.
   * It also provides access to the related {@link DurationFieldType}s.
   * <p>
   * Instances of <code>DateTimeFieldType</code> are singletons.
   * They can be compared using <code>==</code>.
   * <p>
   * If required, you can create your own field, for example a quarterOfYear.
   * You must create a subclass of <code>DateTimeFieldType</code> that defines the field type.
   * This class returns the actual calculation engine from {@link #getField(Chronology)}.
   * The subclass should implement equals and hashCode.
   *
   * @author Stephen Colebourne
   * @author Brian S O'Neill
   * @since 1.0
   */
  public abstract class DateTimeFieldType implements Serializable {
  
      /** Serialization version */
      private static final long serialVersionUID = -42615285973990L;
  
      /** Ordinal values for standard field types. */
      static final byte
          ERA = 1,
          YEAR_OF_ERA = 2,
          CENTURY_OF_ERA = 3,
          YEAR_OF_CENTURY = 4,
          YEAR = 5,
          DAY_OF_YEAR = 6,
          MONTH_OF_YEAR = 7,
          DAY_OF_MONTH = 8,
          WEEKYEAR_OF_CENTURY = 9,
          WEEKYEAR = 10,
          WEEK_OF_WEEKYEAR = 11,
          DAY_OF_WEEK = 12,
          HALFDAY_OF_DAY = 13,
          HOUR_OF_HALFDAY = 14,
          CLOCKHOUR_OF_HALFDAY = 15,
          CLOCKHOUR_OF_DAY = 16,
          HOUR_OF_DAY = 17,
          MINUTE_OF_DAY = 18,
          MINUTE_OF_HOUR = 19,
          SECOND_OF_DAY = 20,
          SECOND_OF_MINUTE = 21,
          MILLIS_OF_DAY = 22,
          MILLIS_OF_SECOND = 23;
  
      /** The era field type. */
      private static final DateTimeFieldType ERA_TYPE = new StandardDateTimeFieldType(
          "era", ERA, DurationFieldType.eras(), null);
      /** The yearOfEra field type. */
      private static final DateTimeFieldType YEAR_OF_ERA_TYPE = new StandardDateTimeFieldType(
          "yearOfEra", YEAR_OF_ERA, DurationFieldType.years(), DurationFieldType.eras());
      /** The centuryOfEra field type. */
      private static final DateTimeFieldType CENTURY_OF_ERA_TYPE = new StandardDateTimeFieldType(
          "centuryOfEra", CENTURY_OF_ERA, DurationFieldType.centuries(), DurationFieldType.eras());
      /** The yearOfCentury field type. */
      private static final DateTimeFieldType YEAR_OF_CENTURY_TYPE = new StandardDateTimeFieldType(
          "yearOfCentury", YEAR_OF_CENTURY, DurationFieldType.years(), DurationFieldType.centuries());
      /** The year field type. */
      private static final DateTimeFieldType YEAR_TYPE = new StandardDateTimeFieldType(
          "year", YEAR, DurationFieldType.years(), null);
      /** The dayOfYear field type. */
      private static final DateTimeFieldType DAY_OF_YEAR_TYPE = new StandardDateTimeFieldType(
          "dayOfYear", DAY_OF_YEAR, DurationFieldType.days(), DurationFieldType.years());
      /** The monthOfYear field type. */
      private static final DateTimeFieldType MONTH_OF_YEAR_TYPE = new StandardDateTimeFieldType(
          "monthOfYear", MONTH_OF_YEAR, DurationFieldType.months(), DurationFieldType.years());
      /** The dayOfMonth field type. */
      private static final DateTimeFieldType DAY_OF_MONTH_TYPE = new StandardDateTimeFieldType(
          "dayOfMonth", DAY_OF_MONTH, DurationFieldType.days(), DurationFieldType.months());
      /** The weekyearOfCentury field type. */
      private static final DateTimeFieldType WEEKYEAR_OF_CENTURY_TYPE = new StandardDateTimeFieldType(
          "weekyearOfCentury", WEEKYEAR_OF_CENTURY, DurationFieldType.weekyears(), DurationFieldType.centuries());
      /** The weekyear field type. */
     private static final DateTimeFieldType WEEKYEAR_TYPE = new StandardDateTimeFieldType(
         "weekyear", WEEKYEAR, DurationFieldType.weekyears(), null);
     /** The weekOfWeekyear field type. */
     private static final DateTimeFieldType WEEK_OF_WEEKYEAR_TYPE = new StandardDateTimeFieldType(
         "weekOfWeekyear", WEEK_OF_WEEKYEAR, DurationFieldType.weeks(), DurationFieldType.weekyears());
     /** The dayOfWeek field type. */
     private static final DateTimeFieldType DAY_OF_WEEK_TYPE = new StandardDateTimeFieldType(
         "dayOfWeek", DAY_OF_WEEK, DurationFieldType.days(), DurationFieldType.weeks());
 
     /** The halfday field type. */
     private static final DateTimeFieldType HALFDAY_OF_DAY_TYPE = new StandardDateTimeFieldType(
         "halfdayOfDay", HALFDAY_OF_DAY, DurationFieldType.halfdays(), DurationFieldType.days());
     /** The hourOfHalfday field type. */
     private static final DateTimeFieldType HOUR_OF_HALFDAY_TYPE = new StandardDateTimeFieldType(
         "hourOfHalfday", HOUR_OF_HALFDAY, DurationFieldType.hours(), DurationFieldType.halfdays());
     /** The clockhourOfHalfday field type. */
     private static final DateTimeFieldType CLOCKHOUR_OF_HALFDAY_TYPE = new StandardDateTimeFieldType(
         "clockhourOfHalfday", CLOCKHOUR_OF_HALFDAY, DurationFieldType.hours(), DurationFieldType.halfdays());
     /** The clockhourOfDay field type. */
     private static final DateTimeFieldType CLOCKHOUR_OF_DAY_TYPE = new StandardDateTimeFieldType(
         "clockhourOfDay", CLOCKHOUR_OF_DAY, DurationFieldType.hours(), DurationFieldType.days());
     /** The hourOfDay field type. */
     private static final DateTimeFieldType HOUR_OF_DAY_TYPE = new StandardDateTimeFieldType(
         "hourOfDay", HOUR_OF_DAY, DurationFieldType.hours(), DurationFieldType.days());
     /** The minuteOfDay field type. */
     private static final DateTimeFieldType MINUTE_OF_DAY_TYPE = new StandardDateTimeFieldType(
         "minuteOfDay", MINUTE_OF_DAY, DurationFieldType.minutes(), DurationFieldType.days());
     /** The minuteOfHour field type. */
     private static final DateTimeFieldType MINUTE_OF_HOUR_TYPE = new StandardDateTimeFieldType(
         "minuteOfHour", MINUTE_OF_HOUR, DurationFieldType.minutes(), DurationFieldType.hours());
     /** The secondOfDay field type. */
     private static final DateTimeFieldType SECOND_OF_DAY_TYPE = new StandardDateTimeFieldType(
         "secondOfDay", SECOND_OF_DAY, DurationFieldType.seconds(), DurationFieldType.days());
     /** The secondOfMinute field type. */
     private static final DateTimeFieldType SECOND_OF_MINUTE_TYPE = new StandardDateTimeFieldType(
         "secondOfMinute", SECOND_OF_MINUTE, DurationFieldType.seconds(), DurationFieldType.minutes());
     /** The millisOfDay field type. */
     private static final DateTimeFieldType MILLIS_OF_DAY_TYPE = new StandardDateTimeFieldType(
         "millisOfDay", MILLIS_OF_DAY, DurationFieldType.millis(), DurationFieldType.days());
     /** The millisOfSecond field type. */
     private static final DateTimeFieldType MILLIS_OF_SECOND_TYPE = new StandardDateTimeFieldType(
         "millisOfSecond", MILLIS_OF_SECOND, DurationFieldType.millis(), DurationFieldType.seconds());
 
     /** The name of the field. */
     private final String iName;
 
     //-----------------------------------------------------------------------
     /**
      * Constructor.
      * 
      * @param name  the name to use
      */
     protected DateTimeFieldType(String name) {
         super();
         iName = name;
     }
 
     //-----------------------------------------------------------------------
     /**
      * Get the millis of second field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType millisOfSecond() {
         return MILLIS_OF_SECOND_TYPE;
     }
 
     /**
      * Get the millis of day field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType millisOfDay() {
         return MILLIS_OF_DAY_TYPE;
     }
 
     /**
      * Get the second of minute field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType secondOfMinute() {
         return SECOND_OF_MINUTE_TYPE;
     }
 
     /**
      * Get the second of day field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType secondOfDay() {
         return SECOND_OF_DAY_TYPE;
     }
 
     /**
      * Get the minute of hour field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType minuteOfHour() {
         return MINUTE_OF_HOUR_TYPE;
     }
 
     /**
      * Get the minute of day field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType minuteOfDay() {
         return MINUTE_OF_DAY_TYPE;
     }
 
     /**
      * Get the hour of day (0-23) field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType hourOfDay() {
         return HOUR_OF_DAY_TYPE;
     }
 
     /**
      * Get the hour of day (offset to 1-24) field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType clockhourOfDay() {
         return CLOCKHOUR_OF_DAY_TYPE;
     }
 
     /**
      * Get the hour of am/pm (0-11) field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType hourOfHalfday() {
         return HOUR_OF_HALFDAY_TYPE;
     }
 
     /**
      * Get the hour of am/pm (offset to 1-12) field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType clockhourOfHalfday() {
         return CLOCKHOUR_OF_HALFDAY_TYPE;
     }
 
     /**
      * Get the AM(0) PM(1) field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType halfdayOfDay() {
         return HALFDAY_OF_DAY_TYPE;
     }
 
     //-----------------------------------------------------------------------
     /**
      * Get the day of week field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType dayOfWeek() {
         return DAY_OF_WEEK_TYPE;
     }
 
     /**
      * Get the day of month field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType dayOfMonth() {
         return DAY_OF_MONTH_TYPE;
     }
 
     /**
      * Get the day of year field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType dayOfYear() {
         return DAY_OF_YEAR_TYPE;
     }
 
     /**
      * Get the week of a week based year field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType weekOfWeekyear() {
         return WEEK_OF_WEEKYEAR_TYPE;
     }
 
     /**
      * Get the year of a week based year field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType weekyear() {
         return WEEKYEAR_TYPE;
     }
 
     /**
      * Get the year of a week based year within a century field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType weekyearOfCentury() {
         return WEEKYEAR_OF_CENTURY_TYPE;
     }
 
     /**
      * Get the month of year field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType monthOfYear() {
         return MONTH_OF_YEAR_TYPE;
     }
 
     /**
      * Get the year field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType year() {
         return YEAR_TYPE;
     }
 
     /**
      * Get the year of era field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType yearOfEra() {
         return YEAR_OF_ERA_TYPE;
     }
 
     /**
      * Get the year of century field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType yearOfCentury() {
         return YEAR_OF_CENTURY_TYPE;
     }
 
     /**
      * Get the century of era field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType centuryOfEra() {
         return CENTURY_OF_ERA_TYPE;
     }
 
     /**
      * Get the era field type.
      * 
      * @return the DateTimeFieldType constant
      */
     public static DateTimeFieldType era() {
         return ERA_TYPE;
     }
 
     //-----------------------------------------------------------------------
     /**
      * Get the name of the field.
      * <p>
      * By convention, names follow a pattern of "dddOfRrr", where "ddd" represents
      * the (singular) duration unit field name and "Rrr" represents the (singular)
      * duration range field name. If the range field is not applicable, then
      * the name of the field is simply the (singular) duration field name.
      * 
      * @return field name
      */
     public String getName() {
         return iName;
     }
 
     /**
      * Get the duration unit of the field.
      * 
      * @return duration unit of the field, never null
      */
     public abstract DurationFieldType getDurationType();
 
     /**
      * Get the duration range of the field.
      * 
      * @return duration range of the field, null if unbounded
      */
     public abstract DurationFieldType getRangeDurationType();
 
     /**
      * Gets a suitable field for this type from the given Chronology.
      *
      * @param chronology  the chronology to use, null means ISOChronology in default zone
      * @return a suitable field
      */
     public abstract DateTimeField getField(Chronology chronology);
 
     /**
      * Checks whether this field supported in the given Chronology.
      *
      * @param chronology  the chronology to use, null means ISOChronology in default zone
      * @return true if supported
      */
     public boolean isSupported(Chronology chronology) {
         return getField(chronology).isSupported();
     }
 
     /**
      * Get a suitable debug string.
      * 
      * @return debug string
      */
     public String toString() {
         return getName();
     }
 
     private static class StandardDateTimeFieldType extends DateTimeFieldType {
         /** Serialization version */
         private static final long serialVersionUID = -9937958251642L;
 
         /** The ordinal of the standard field type, for switch statements */
         private final byte iOrdinal;
 
         /** The unit duration of the field. */
         private final transient DurationFieldType iUnitType;
         /** The range duration of the field. */
         private final transient DurationFieldType iRangeType;
 
         /**
          * Constructor.
          * 
          * @param name  the name to use
          * @param ordinal  the byte value for the oridinal index
          * @param unitType  the unit duration type
          * @param rangeType  the range duration type
          */
         StandardDateTimeFieldType(String name, byte ordinal,
                                   DurationFieldType unitType, DurationFieldType rangeType) {
             super(name);
             iOrdinal = ordinal;
             iUnitType = unitType;
             iRangeType = rangeType;
         }
 
         /** @inheritdoc */
         public DurationFieldType getDurationType() {
             return iUnitType;
         }
 
         /** @inheritdoc */
         public DurationFieldType getRangeDurationType() {
             return iRangeType;
         }
 
         /** @inheritdoc */
         @Override
         public boolean equals(Object obj) {
             if (this == obj) {
                 return true;
             }
             if (obj instanceof StandardDateTimeFieldType) {
                 return iOrdinal == ((StandardDateTimeFieldType) obj).iOrdinal;
             }
             return false;
         }
 
         /** @inheritdoc */
         @Override
         public int hashCode() {
             return (1 << iOrdinal);
         }
 
         /** @inheritdoc */
         public DateTimeField getField(Chronology chronology) {
             chronology = DateTimeUtils.getChronology(chronology);
 
             switch (iOrdinal) {
                 case ERA:
                     return chronology.era();
                 case YEAR_OF_ERA:
                     return chronology.yearOfEra();
                 case CENTURY_OF_ERA:
                     return chronology.centuryOfEra();
                 case YEAR_OF_CENTURY:
                     return chronology.yearOfCentury();
                 case YEAR:
                     return chronology.year();
                 case DAY_OF_YEAR:
                     return chronology.dayOfYear();
                 case MONTH_OF_YEAR:
                     return chronology.monthOfYear();
                 case DAY_OF_MONTH:
                     return chronology.dayOfMonth();
                 case WEEKYEAR_OF_CENTURY:
                     return chronology.weekyearOfCentury();
                 case WEEKYEAR:
                     return chronology.weekyear();
                 case WEEK_OF_WEEKYEAR:
                     return chronology.weekOfWeekyear();
                 case DAY_OF_WEEK:
                     return chronology.dayOfWeek();
                 case HALFDAY_OF_DAY:
                     return chronology.halfdayOfDay();
                 case HOUR_OF_HALFDAY:
                     return chronology.hourOfHalfday();
                 case CLOCKHOUR_OF_HALFDAY:
                     return chronology.clockhourOfHalfday();
                 case CLOCKHOUR_OF_DAY:
                     return chronology.clockhourOfDay();
                 case HOUR_OF_DAY:
                     return chronology.hourOfDay();
                 case MINUTE_OF_DAY:
                     return chronology.minuteOfDay();
                 case MINUTE_OF_HOUR:
                     return chronology.minuteOfHour();
                 case SECOND_OF_DAY:
                     return chronology.secondOfDay();
                 case SECOND_OF_MINUTE:
                     return chronology.secondOfMinute();
                 case MILLIS_OF_DAY:
                     return chronology.millisOfDay();
                 case MILLIS_OF_SECOND:
                     return chronology.millisOfSecond();
                 default:
                     // Shouldn't happen.
                     throw new InternalError();
             }
         }
 
         /**
          * Ensure a singleton is returned.
          * 
          * @return the singleton type
          */
         private Object readResolve() {
             switch (iOrdinal) {
                 case ERA:
                     return ERA_TYPE;
                 case YEAR_OF_ERA:
                     return YEAR_OF_ERA_TYPE;
                 case CENTURY_OF_ERA:
                     return CENTURY_OF_ERA_TYPE;
                 case YEAR_OF_CENTURY:
                     return YEAR_OF_CENTURY_TYPE;
                 case YEAR:
                     return YEAR_TYPE;
                 case DAY_OF_YEAR:
                     return DAY_OF_YEAR_TYPE;
                 case MONTH_OF_YEAR:
                     return MONTH_OF_YEAR_TYPE;
                 case DAY_OF_MONTH:
                     return DAY_OF_MONTH_TYPE;
                 case WEEKYEAR_OF_CENTURY:
                     return WEEKYEAR_OF_CENTURY_TYPE;
                 case WEEKYEAR:
                     return WEEKYEAR_TYPE;
                 case WEEK_OF_WEEKYEAR:
                     return WEEK_OF_WEEKYEAR_TYPE;
                 case DAY_OF_WEEK:
                     return DAY_OF_WEEK_TYPE;
                 case HALFDAY_OF_DAY:
                     return HALFDAY_OF_DAY_TYPE;
                 case HOUR_OF_HALFDAY:
                     return HOUR_OF_HALFDAY_TYPE;
                 case CLOCKHOUR_OF_HALFDAY:
                     return CLOCKHOUR_OF_HALFDAY_TYPE;
                 case CLOCKHOUR_OF_DAY:
                     return CLOCKHOUR_OF_DAY_TYPE;
                 case HOUR_OF_DAY:
                     return HOUR_OF_DAY_TYPE;
                 case MINUTE_OF_DAY:
                     return MINUTE_OF_DAY_TYPE;
                 case MINUTE_OF_HOUR:
                     return MINUTE_OF_HOUR_TYPE;
                 case SECOND_OF_DAY:
                     return SECOND_OF_DAY_TYPE;
                 case SECOND_OF_MINUTE:
                     return SECOND_OF_MINUTE_TYPE;
                 case MILLIS_OF_DAY:
                     return MILLIS_OF_DAY_TYPE;
                 case MILLIS_OF_SECOND:
                     return MILLIS_OF_SECOND_TYPE;
                 default:
                     // Shouldn't happen.
                     return this;
             }
         }
     }
 
 }