1/*
2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package com.sun.xml.internal.xsom.util;
27
28import java.util.ArrayList;
29import java.util.Collection;
30import java.util.Iterator;
31import java.util.List;
32import java.util.NoSuchElementException;
33
34/**
35 * {@link Collection} that returns the view of objects which are actually fetched
36 * lazily from an {@link Iterator}.
37 *
38 * @author Kohsuke Kawaguchi
39 */
40public class DeferedCollection<T> implements Collection<T> {
41    /**
42     * The iterator that lazily evaluates SCD query.
43     */
44    private final Iterator<T> result;
45
46    /**
47     * Stores values that are already fetched from {@link #result}.
48     */
49    private final List<T> archive = new ArrayList<T>();
50
51    public DeferedCollection(Iterator<T> result) {
52        this.result = result;
53    }
54
55    public boolean isEmpty() {
56        if(archive.isEmpty())
57            fetch();
58        return archive.isEmpty();
59    }
60
61    public int size() {
62        fetchAll();
63        return archive.size();
64    }
65
66    public boolean contains(Object o) {
67        if(archive.contains(o))
68            return true;
69        while(result.hasNext()) {
70            T value = result.next();
71            archive.add(value);
72            if(value.equals(o))
73                return true;
74        }
75        return false;
76    }
77
78    public boolean containsAll(Collection<?> c) {
79        for (Object o : c) {
80            if(!contains(o))
81                return false;
82        }
83        return true;
84    }
85
86    public Iterator<T> iterator() {
87        return new Iterator<T>() {
88            int idx=0;
89            public boolean hasNext() {
90                if(idx<archive.size())
91                    return true;
92                return result.hasNext();
93            }
94
95            public T next() {
96                if(idx==archive.size())
97                    fetch();
98                if(idx==archive.size())
99                    throw new NoSuchElementException();
100                return archive.get(idx++);
101            }
102
103            public void remove() {
104                // TODO
105            }
106        };
107    }
108
109    public Object[] toArray() {
110        fetchAll();
111        return archive.toArray();
112    }
113
114    public <T>T[] toArray(T[] a) {
115        fetchAll();
116        return archive.toArray(a);
117    }
118
119
120
121    private void fetchAll() {
122        while(result.hasNext())
123            archive.add(result.next());
124    }
125
126    /**
127     * Fetches another item from {@link
128     */
129    private void fetch() {
130        if(result.hasNext())
131            archive.add(result.next());
132    }
133
134// mutation methods are unsupported
135    public boolean add(T o) {
136        throw new UnsupportedOperationException();
137    }
138
139    public boolean remove(Object o) {
140        throw new UnsupportedOperationException();
141    }
142
143    public boolean addAll(Collection<? extends T> c) {
144        throw new UnsupportedOperationException();
145    }
146
147    public boolean removeAll(Collection<?> c) {
148        throw new UnsupportedOperationException();
149    }
150
151    public boolean retainAll(Collection<?> c) {
152        throw new UnsupportedOperationException();
153    }
154
155    public void clear() {
156        throw new UnsupportedOperationException();
157    }
158}
159