1/*
2 * Copyright (C) 2015 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.camera.captureintent.stateful;
18
19import javax.annotation.Nonnull;
20
21/**
22 * Defines a state machine interface that any implementation of this interface
23 * is able to transition among different {@link State} and process various
24 * {@link Event}.
25 */
26public interface StateMachine {
27    /**
28     * Obtains the current state.
29     *
30     * @return A {@link State} object that represents the current state.
31     */
32    public State getCurrentState();
33
34    /**
35     * Sets the initial state of the state machine.
36     *
37     * @param initialState An initial {@link State}.
38     * @return True if the operation is succeeded.
39     */
40    public boolean setInitialState(@Nonnull State initialState);
41
42    /**
43     * Process a specified {@link Event} and potentially change the current
44     * state.
45     *
46     * This method is thread-safe so it could be called on different threads.
47     * Only one event could be processed at a time.
48     *
49     * @param event An {@link Event} to be processed.
50     */
51    public void processEvent(Event event);
52}
53