1 /*
2  * Copyright (C) 2009 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.contacts;
18 
19 import android.content.Context;
20 
21 import java.util.Iterator;
22 import java.util.List;
23 
24 /**
25  * Class used for collapsing data items into groups of similar items. The data items that should be
26  * collapsible should implement the Collapsible interface. The class also contains a utility
27  * function that takes an ArrayList of items and returns a list of the same items collapsed into
28  * groups.
29  */
30 public final class Collapser {
31 
32     /*
33      * This utility class cannot be instantiated.
34      */
Collapser()35     private Collapser() {}
36 
37     /*
38      * The Collapser uses an n^2 algorithm so we don't want it to run on
39      * lists beyond a certain size. This specifies the maximum size to collapse.
40      */
41     private static final int MAX_LISTSIZE_TO_COLLAPSE = 20;
42 
43     /*
44      * Interface implemented by data types that can be collapsed into groups of similar data. This
45      * can be used for example to collapse similar contact data items into a single item.
46      */
47     public interface Collapsible<T> {
collapseWith(T t)48         public void collapseWith(T t);
shouldCollapseWith(T t, Context context)49         public boolean shouldCollapseWith(T t, Context context);
50 
51     }
52 
53     /**
54      * Collapses a list of Collapsible items into a list of collapsed items. Items are collapsed
55      * if {@link Collapsible#shouldCollapseWith(Object)} returns true, and are collapsed
56      * through the {@Link Collapsible#collapseWith(Object)} function implemented by the data item.
57      *
58      * @param list List of Objects of type <T extends Collapsible<T>> to be collapsed.
59      */
collapseList(List<T> list, Context context)60     public static <T extends Collapsible<T>> void collapseList(List<T> list, Context context) {
61 
62         int listSize = list.size();
63         // The algorithm below is n^2 so don't run on long lists
64         if (listSize > MAX_LISTSIZE_TO_COLLAPSE) {
65             return;
66         }
67 
68         for (int i = 0; i < listSize; i++) {
69             T iItem = list.get(i);
70             if (iItem != null) {
71                 for (int j = i + 1; j < listSize; j++) {
72                     T jItem = list.get(j);
73                     if (jItem != null) {
74                         if (iItem.shouldCollapseWith(jItem, context)) {
75                             iItem.collapseWith(jItem);
76                             list.set(j, null);
77                         } else if (jItem.shouldCollapseWith(iItem, context)) {
78                             jItem.collapseWith(iItem);
79                             list.set(i, null);
80                             break;
81                         }
82                     }
83                 }
84             }
85         }
86 
87         // Remove the null items
88         Iterator<T> itr = list.iterator();
89         while (itr.hasNext()) {
90             if (itr.next() == null) {
91                 itr.remove();
92             }
93         }
94 
95     }
96 }
97