001/*
002 *  Copyright 2001-2007 Stephen Colebourne
003 *
004 *  Licensed under the Apache License, Version 2.0 (the "License");
005 *  you may not use this file except in compliance with the License.
006 *  You may obtain a copy of the License at
007 *
008 *      http://www.apache.org/licenses/LICENSE-2.0
009 *
010 *  Unless required by applicable law or agreed to in writing, software
011 *  distributed under the License is distributed on an "AS IS" BASIS,
012 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 *  See the License for the specific language governing permissions and
014 *  limitations under the License.
015 */
016package org.joda.time.field;
017
018import org.joda.time.Chronology;
019import org.joda.time.DateTimeField;
020
021/**
022 * Converts a strict DateTimeField into a lenient one. By being lenient, the
023 * set method accepts out of bounds values, performing an addition instead.
024 * <p>
025 * LenientDateTimeField is thread-safe and immutable.
026 *
027 * @author Brian S O'Neill
028 * @see org.joda.time.chrono.LenientChronology
029 * @see StrictDateTimeField
030 * @since 1.0
031 */
032public class LenientDateTimeField extends DelegatedDateTimeField {
033
034    private static final long serialVersionUID = 8714085824173290599L;
035
036    private final Chronology iBase;
037
038    /**
039     * Returns a lenient version of the given field. If it is already lenient,
040     * then it is returned as-is. Otherwise, a new LenientDateTimeField is
041     * returned.
042     */
043    public static DateTimeField getInstance(DateTimeField field, Chronology base) {
044        if (field == null) {
045            return null;
046        }
047        if (field instanceof StrictDateTimeField) {
048            field = ((StrictDateTimeField)field).getWrappedField();
049        }
050        if (field.isLenient()) {
051            return field;
052        }
053        return new LenientDateTimeField(field, base);
054    }
055
056    protected LenientDateTimeField(DateTimeField field, Chronology base) {
057        super(field);
058        iBase = base;
059    }
060
061    public final boolean isLenient() {
062        return true;
063    }
064
065    /**
066     * Set values which may be out of bounds by adding the difference between
067     * the new value and the current value.
068     */
069    public long set(long instant, int value) {
070        // lenient needs to handle time zone chronologies
071        // so we do the calculation using local milliseconds
072        long localInstant = iBase.getZone().convertUTCToLocal(instant);
073        long difference = FieldUtils.safeSubtract(value, get(instant));
074        localInstant = getType().getField(iBase.withUTC()).add(localInstant, difference);
075        return iBase.getZone().convertLocalToUTC(localInstant, false, instant);
076    }
077}