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     */
016    package org.joda.time.field;
017    
018    import org.joda.time.Chronology;
019    import 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     */
032    public 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    }