1/*
2 * Copyright 2017 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 androidx.recyclerview.selection;
18
19import static androidx.core.util.Preconditions.checkArgument;
20import static androidx.core.util.Preconditions.checkState;
21
22import android.view.MotionEvent;
23
24import androidx.annotation.NonNull;
25import androidx.annotation.Nullable;
26
27import java.util.Arrays;
28import java.util.List;
29
30/**
31 * Registry for tool specific event handler. This provides map like functionality,
32 * along with fallback to a default handler, while avoiding auto-boxing of tool
33 * type values that would be necessitated where a Map used.
34 *
35 * @param <T> type of item being registered.
36 */
37final class ToolHandlerRegistry<T> {
38
39    // Currently there are four known input types. ERASER is the last one, so has the
40    // highest value. UNKNOWN is zero, so we add one. This allows delegates to be
41    // registered by type, and avoid the auto-boxing that would be necessary were we
42    // to store delegates in a Map<Integer, Delegate>.
43    private static final int NUM_INPUT_TYPES = MotionEvent.TOOL_TYPE_ERASER + 1;
44
45    private final List<T> mHandlers = Arrays.asList(null, null, null, null, null);
46    private final T mDefault;
47
48    ToolHandlerRegistry(@NonNull T defaultDelegate) {
49        checkArgument(defaultDelegate != null);
50        mDefault = defaultDelegate;
51
52        // Initialize all values to null.
53        for (int i = 0; i < NUM_INPUT_TYPES; i++) {
54            mHandlers.set(i, null);
55        }
56    }
57
58    /**
59     * @param toolType
60     * @param delegate the delegate, or null to unregister.
61     * @throws IllegalStateException if an tooltype handler is already registered.
62     */
63    void set(int toolType, @Nullable T delegate) {
64        checkArgument(toolType >= 0 && toolType <= MotionEvent.TOOL_TYPE_ERASER);
65        checkState(mHandlers.get(toolType) == null);
66
67        mHandlers.set(toolType, delegate);
68    }
69
70    T get(@NonNull MotionEvent e) {
71        T d = mHandlers.get(e.getToolType(0));
72        return d != null ? d : mDefault;
73    }
74}
75