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      1 /*
      2  * Copyright (C) 2013 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.camera.data;
     18 
     19 import com.google.common.base.Preconditions;
     20 
     21 import java.util.Comparator;
     22 import java.util.Date;
     23 
     24 /**
     25  * Sort filmstrip items by newest first, then by most recently modified
     26  * then by title comparison.
     27  */
     28 public class NewestFirstComparator implements Comparator<FilmstripItem> {
     29     private final Date mNow;
     30 
     31     private static final int MILLIS_IN_DAY = 24 * 60 * 60 * 1000;
     32 
     33     /**
     34      * Construct a comparator that sorts items by newest first. We ignore future
     35      * creation dates using the supplied current date as a baseline.
     36      *
     37      * @param now present date to be used in comparisons to rule out dates in
     38      *            the future.
     39      */
     40     public NewestFirstComparator(Date now) {
     41         Preconditions.checkNotNull(now);
     42         // Buffer by 24 hours to protect against false positives due to intraday
     43         // time zone issues.
     44         mNow = new Date(now.getTime() + MILLIS_IN_DAY);
     45     }
     46 
     47     @Override
     48     public int compare(FilmstripItem d1, FilmstripItem d2) {
     49         FilmstripItemData d1Data = d1.getData();
     50         FilmstripItemData d2Data = d2.getData();
     51 
     52         // If creation date is in future, fall back to modified, b/19565464.
     53         Date d1PrimaryDate = isFuture(d1Data.getCreationDate()) ?
     54                 d1Data.getLastModifiedDate() : d1Data.getCreationDate();
     55         Date d2PrimaryDate = isFuture(d2Data.getCreationDate()) ?
     56                 d2Data.getLastModifiedDate() : d2Data.getCreationDate();
     57 
     58         int cmp = compareDate(d1PrimaryDate, d2PrimaryDate);
     59         if (cmp == 0) {
     60             cmp = compareDate(d1Data.getLastModifiedDate(),
     61                   d2Data.getLastModifiedDate());
     62         }
     63         if (cmp == 0) {
     64             cmp = d1Data.getTitle().compareTo(d2Data.getTitle());
     65         }
     66         return cmp;
     67     }
     68 
     69     /**
     70      * Normal date comparison will sort these oldest first,
     71      * so invert the order by multiplying by -1.
     72      */
     73     private int compareDate(Date v1, Date v2) {
     74         return v1.compareTo(v2) * -1;
     75     }
     76 
     77     /**
     78      * Is the Date in the future from a base date. If the date is in the future
     79      * (larger) than the base date provided, return true.
     80      *
     81      * @param date The date to check whether it is in the future
     82      * @param base The date to use as a baseline 'present'
     83      * @return true if date is in the future from base
     84      */
     85     private boolean isFuture(Date date) {
     86         return mNow.compareTo(date) < 0;
     87     }
     88 }