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
17package com.android.loaderapp.model;
18
19import java.util.ArrayList;
20import java.util.Iterator;
21
22/**
23 * Class used for collapsing data items into groups of similar items. The data items that should be
24 * collapsible should implement the Collapsible interface. The class also contains a utility
25 * function that takes an ArrayList of items and returns a list of the same items collapsed into
26 * groups.
27 */
28public final class Collapser {
29
30    /*
31     * This utility class cannot be instantiated.
32     */
33    private Collapser() {}
34
35    /*
36     * Interface implemented by data types that can be collapsed into groups of similar data. This
37     * can be used for example to collapse similar contact data items into a single item.
38     */
39    public interface Collapsible<T> {
40        public boolean collapseWith(T t);
41        public boolean shouldCollapseWith(T t);
42    }
43
44    /**
45     * Collapses a list of Collapsible items into a list of collapsed items. Items are collapsed
46     * if {@link Collapsible#shouldCollapseWith(Object) return strue, and are collapsed
47     * through the {@Link Collapsible#collapseWith(Object)} function implemented by the data item.
48     *
49     * @param list ArrayList of Objects of type <T extends Collapsible<T>> to be collapsed.
50     */
51    public static <T extends Collapsible<T>> void collapseList(ArrayList<T> list) {
52
53        int listSize = list.size();
54
55        for (int i = 0; i < listSize; i++) {
56            T iItem = list.get(i);
57            if (iItem != null) {
58                for (int j = i + 1; j < listSize; j++) {
59                    T jItem = list.get(j);
60                    if (jItem != null) {
61                        if (iItem.shouldCollapseWith(jItem)) {
62                            iItem.collapseWith(jItem);
63                            list.set(j, null);
64                        }
65                    }
66                }
67            }
68        }
69
70        // Remove the null items
71        Iterator<T> itr = list.iterator();
72        while (itr.hasNext()) {
73            if (itr.next() == null) {
74                itr.remove();
75            }
76        }
77
78    }
79}
80