/*
 *  Copyright 2001-2009 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.field;

import java.io.Serializable;

import org.joda.time.DurationField;
import org.joda.time.DurationFieldType;

BaseDurationField provides the common behaviour for DurationField
implementations.

This class should generally not be used directly by API users. The
DurationField class should be used when different kinds of DurationField
objects are to be referenced.

BaseDurationField is thread-safe and immutable, and its subclasses must
be as well.
Author:
Brian S O'Neill
See Also:
DecoratedDurationField
Since:
1.0/**
 * BaseDurationField provides the common behaviour for DurationField
 * implementations.
 * <p>
 * This class should generally not be used directly by API users. The
 * DurationField class should be used when different kinds of DurationField
 * objects are to be referenced.
 * <p>
 * BaseDurationField is thread-safe and immutable, and its subclasses must
 * be as well.
 *
 * @author Brian S O'Neill
 * @see DecoratedDurationField
 * @since 1.0
 */
public abstract class BaseDurationField extends DurationField implements Serializable {

    
Serialization lock. /** Serialization lock. */
    private static final long serialVersionUID = -2554245107589433218L;

    
A descriptive name for the field. /** A descriptive name for the field. */
    private final DurationFieldType iType;

    protected BaseDurationField(DurationFieldType type) {
        super();
        if (type == null) {
            throw new IllegalArgumentException("The type must not be null");
        }
        iType = type;
    }

    public final DurationFieldType getType() {
        return iType;
    }

    public final String getName() {
        return iType.getName();
    }

    
Returns:
true always/**
     * @return true always
     */
    public final boolean isSupported() {
        return true;
    }

    //------------------------------------------------------------------------
    
Get the value of this field from the milliseconds, which is approximate
if this field is imprecise.
Params:
duration –  the milliseconds to query, which may be negative
Returns:
the value of the field, in the units of the field, which may be
negative/**
     * Get the value of this field from the milliseconds, which is approximate
     * if this field is imprecise.
     *
     * @param duration  the milliseconds to query, which may be negative
     * @return the value of the field, in the units of the field, which may be
     * negative
     */
    public int getValue(long duration) {
        return FieldUtils.safeToInt(getValueAsLong(duration));
    }

    
Get the value of this field from the milliseconds, which is approximate
if this field is imprecise.
Params:
duration –  the milliseconds to query, which may be negative
Returns:
the value of the field, in the units of the field, which may be
negative/**
     * Get the value of this field from the milliseconds, which is approximate
     * if this field is imprecise.
     *
     * @param duration  the milliseconds to query, which may be negative
     * @return the value of the field, in the units of the field, which may be
     * negative
     */
    public long getValueAsLong(long duration) {
        return duration / getUnitMillis();
    }

    
Get the value of this field from the milliseconds relative to an
instant.
If the milliseconds is positive, then the instant is treated as a
"start instant". If negative, the instant is treated as an "end
instant".
The default implementation returns
Utils.safeToInt(getAsLong(millisDuration, instant)).
Params:
duration –  the milliseconds to query, which may be negative
instant –  the start instant to calculate relative to
Returns:
the value of the field, in the units of the field, which may be
negative/**
     * Get the value of this field from the milliseconds relative to an
     * instant.
     *
     * <p>If the milliseconds is positive, then the instant is treated as a
     * "start instant". If negative, the instant is treated as an "end
     * instant".
     *
     * <p>The default implementation returns
     * <code>Utils.safeToInt(getAsLong(millisDuration, instant))</code>.
     * 
     * @param duration  the milliseconds to query, which may be negative
     * @param instant  the start instant to calculate relative to
     * @return the value of the field, in the units of the field, which may be
     * negative
     */
    public int getValue(long duration, long instant) {
        return FieldUtils.safeToInt(getValueAsLong(duration, instant));
    }

    
Get the millisecond duration of this field from its value, which is
approximate if this field is imprecise.
Params:
value –  the value of the field, which may be negative
Returns:
the milliseconds that the field represents, which may be
negative/**
     * Get the millisecond duration of this field from its value, which is
     * approximate if this field is imprecise.
     * 
     * @param value  the value of the field, which may be negative
     * @return the milliseconds that the field represents, which may be
     * negative
     */
    public long getMillis(int value) {
        return value * getUnitMillis();  // safe
    }

    
Get the millisecond duration of this field from its value, which is
approximate if this field is imprecise.
Params:
value –  the value of the field, which may be negative
Returns:
the milliseconds that the field represents, which may be
negative/**
     * Get the millisecond duration of this field from its value, which is
     * approximate if this field is imprecise.
     * 
     * @param value  the value of the field, which may be negative
     * @return the milliseconds that the field represents, which may be
     * negative
     */
    public long getMillis(long value) {
        return FieldUtils.safeMultiply(value, getUnitMillis());
    }

    // Calculation API
    //------------------------------------------------------------------------
    public int getDifference(long minuendInstant, long subtrahendInstant) {
        return FieldUtils.safeToInt(getDifferenceAsLong(minuendInstant, subtrahendInstant));
    }

    //------------------------------------------------------------------------
    public int compareTo(DurationField otherField) {
        long otherMillis = otherField.getUnitMillis();
        long thisMillis = getUnitMillis();
        // cannot do (thisMillis - otherMillis) as can overflow
        if (thisMillis == otherMillis) {
            return 0;
        }
        if (thisMillis < otherMillis) {
            return -1;
        } else {
            return 1;
        }
    }

    
Get a suitable debug string.
Returns:
debug string/**
     * Get a suitable debug string.
     * 
     * @return debug string
     */
    public String toString() {
        return "DurationField[" + getName() + ']';
    }

}