001/*
002 * #%L
003 * GwtMaterial
004 * %%
005 * Copyright (C) 2015 - 2017 GwtMaterialDesign
006 * %%
007 * Licensed under the Apache License, Version 2.0 (the "License");
008 * you may not use this file except in compliance with the License.
009 * You may obtain a copy of the License at
010 * 
011 *      http://www.apache.org/licenses/LICENSE-2.0
012 * 
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 * #L%
019 */
020package gwt.material.design.client.data.infinite;
021
022import java.util.ArrayList;
023import java.util.List;
024
025/**
026 * A Data Source for the {@link InfiniteDataView}, supports asynchronous calls
027 * expecting that {@link InfiniteDataView#loaded(int, List, int, boolean)} is called when ready.
028 * <br><br>
029 * <b>Note</b> that if {@link InfiniteDataView#loaded(int, List, int, boolean)} is not called
030 * the data will not be populated.
031 *
032 * @author Ben Dol
033 */
034public class InfiniteDataCache<T> extends ArrayList<T> {
035
036    public List<T> getCache(int startIndex, int viewSize) {
037        int size = size();
038        int end = (startIndex + viewSize);
039
040        List<T> cache = new ArrayList<>();
041        if(startIndex < size && end <= size) {
042            for(int i = startIndex; i < end; i++) {
043                T data = get(i);
044                if(data != null) {
045                    cache.add(data);
046                } else {
047                    // If any data record is null we
048                    // need to invoke a full data request
049                    cache.clear();
050                    break;
051                }
052            }
053        }
054        return cache;
055    }
056
057    public void addCache(int startIndex, List<T> data) {
058        // Create placeholders up to the specified index.
059        int cacheOffset = Math.max(0, startIndex - size());
060        for (int i = 0; i < cacheOffset; i++) {
061            add(null);
062        }
063
064        // Insert the new values into the data array.
065        for (int i = startIndex; i < startIndex + data.size(); i++) {
066            T value = data.get(i - startIndex);
067            if (i < size()) {
068                set(i, value);
069            } else {
070                add(value);
071            }
072        }
073    }
074}