/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.inputmethod.event;

import com.android.inputmethod.latin.utils.CollectionUtils;

import java.util.ArrayList;

/**
 * This class implements the logic chain between receiving events and generating code points.
 *
 * Event sources are multiple. It may be a hardware keyboard, a D-PAD, a software keyboard,
 * or any exotic input source.
 * This class will orchestrate the composing chain that starts with an event as its input. Each
 * composer will be given turns one after the other.
 * The output is composed of two sequences of code points: the first, representing the already
 * finished combining part, will be shown normally as the composing string, while the second is
 * feedback on the composing state and will typically be shown with different styling such as
 * a colored background.
 */
public class CombinerChain {
    // TODO: Create an object type to represent input material + visual feedback + decoding state

    private final ArrayList<Combiner> mCombiners;

    /**
     * Create an combiner chain.
     *
     * The combiner chain takes events as inputs and outputs code points and combining state.
     * For example, if the input language is Japanese, the combining chain will typically perform
     * kana conversion.
     *
     * @param combinerList A list of combiners to be applied in order.
     */
    public CombinerChain(final Combiner... combinerList) {
        mCombiners = CollectionUtils.newArrayList();
        // The dead key combiner is always active, and always first
        mCombiners.add(new DeadKeyCombiner());
    }

    // Pass a new event through the whole chain.
    public void processEvent(final ArrayList<Event> previousEvents, final Event newEvent) {
        final ArrayList<Event> modifiablePreviousEvents = new ArrayList<Event>(previousEvents);
        Event event = newEvent;
        for (final Combiner combiner : mCombiners) {
            // A combiner can never return more than one event; it can return several
            // code points, but they should be encapsulated within one event.
            event = combiner.processEvent(modifiablePreviousEvents, event);
            if (null == event) {
                // Combiners return null if they eat the event.
                return;
            }
        }
    }
}