/*
 * Copyright (c) 2008-2017, Hazelcast, Inc. All Rights Reserved.
 *
 * 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.hazelcast.client.impl.protocol.util;

import com.hazelcast.client.impl.protocol.ClientMessage;
import com.hazelcast.internal.networking.ChannelInboundHandler;
import com.hazelcast.internal.util.counters.SwCounter;
import com.hazelcast.util.collection.Long2ObjectHashMap;

import java.nio.ByteBuffer;

import static com.hazelcast.client.impl.protocol.ClientMessage.BEGIN_AND_END_FLAGS;
import static com.hazelcast.client.impl.protocol.ClientMessage.BEGIN_FLAG;
import static com.hazelcast.client.impl.protocol.ClientMessage.END_FLAG;

/**
 * Builds {@link ClientMessage}s from byte chunks. Fragmented messages are merged into single messages before processed.
 */
public class ClientMessageChannelInboundHandler implements ChannelInboundHandler {

    private final Long2ObjectHashMap<BufferBuilder> builderBySessionIdMap = new Long2ObjectHashMap<BufferBuilder>();

    private final MessageHandler delegate;
    private final SwCounter messageCounter;
    private ClientMessage message = ClientMessage.create();

    public ClientMessageChannelInboundHandler(SwCounter messageCounter, MessageHandler messageHandler) {
        this.messageCounter = messageCounter;
        this.delegate = messageHandler;
    }

    @Override
    public void onRead(ByteBuffer src) throws Exception {
        int messagesCreated = 0;
        while (src.hasRemaining()) {
            final boolean complete = message.readFrom(src);
            if (!complete) {
                messageCounter.inc(messagesCreated);
                return;
            }

            //MESSAGE IS COMPLETE HERE
            if (message.isFlagSet(BEGIN_AND_END_FLAGS)) {
                //HANDLE-MESSAGE
                handleMessage(message);
                message = ClientMessage.create();
                messagesCreated++;
                continue;
            }

            // first fragment
            if (message.isFlagSet(BEGIN_FLAG)) {
                final BufferBuilder builder = new BufferBuilder();
                builderBySessionIdMap.put(message.getCorrelationId(), builder);
                builder.append(message.buffer(), 0, message.getFrameLength());
            } else {
                final BufferBuilder builder = builderBySessionIdMap.get(message.getCorrelationId());
                if (builder.position() == 0) {
                    throw new IllegalStateException();
                }

                builder.append(message.buffer(), message.getDataOffset(), message.getFrameLength() - message.getDataOffset());

                if (message.isFlagSet(END_FLAG)) {
                    final int msgLength = builder.position();
                    ClientMessage cm = ClientMessage.createForDecode(builder.buffer(), 0);
                    cm.setFrameLength(msgLength);
                    //HANDLE-MESSAGE
                    handleMessage(cm);
                    builderBySessionIdMap.remove(message.getCorrelationId());

                }
            }

            message = ClientMessage.create();
            messagesCreated++;
        }
    }

    private void handleMessage(ClientMessage message) {
        message.index(message.getDataOffset());
        delegate.handleMessage(message);
    }

    /**
     * Implementers will be responsible to delegate the constructed message
     */
    public interface MessageHandler {

        /**
         * Received message to be processed
         *
         * @param message the ClientMessage
         */
        void handleMessage(ClientMessage message);
    }


}