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Modules for controlling the data flow in a Metafacture pipeline
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/*
 * Copyright 2013, 2014 Deutsche Nationalbibliothek
 *
 * 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 org.metafacture.flowcontrol;

import org.metafacture.framework.StreamPipe;
import org.metafacture.framework.StreamReceiver;
import org.metafacture.framework.helpers.DefaultStreamPipe;

import java.util.ArrayList;
import java.util.List;

/**
 * {@link StreamPipe} which buffers incoming records and replays them upon
 * request.
 *
 * @author Markus Michael Geipel
 *
 */
public final class StreamBuffer extends DefaultStreamPipe {

    /**
     * Defines entity and literal message types.
     */
    private enum MessageType {
        RECORD_START, RECORD_END, ENTITY_START, ENTITY_END, LITERAL
    }

    private final List typeBuffer = new ArrayList();
    private final List valueBuffer = new ArrayList();

    /**
     * Creates an instance of {@link StreamBuffer}.
     */
    public StreamBuffer() {
    }

    /**
     * Checks whether there are messages stored.
     *
     * @return true if messages are empty, otherwise false
     */
    public boolean isEmpty() {
        return typeBuffer.isEmpty();
    }

    /**
     * Replays the buffered event.
     */
    public void replay() {

        int index = 0;
        for (final MessageType type : typeBuffer) {
            switch (type) {
                case RECORD_START:
                    getReceiver().startRecord(valueBuffer.get(index));
                    ++index;
                    break;
                case RECORD_END:
                    getReceiver().endRecord();
                    break;

                case ENTITY_START:
                    getReceiver().startEntity(valueBuffer.get(index));
                    ++index;
                    break;
                case ENTITY_END:
                    getReceiver().endEntity();
                    break;
                default:
                    getReceiver().literal(valueBuffer.get(index), valueBuffer.get(index + 1));
                    index += 2;
                    break;
            }
        }
    }

    /**
     * Clears the buffer.
     */
    public void clear() {
        typeBuffer.clear();
        valueBuffer.clear();
    }

    @Override
    public void startRecord(final String identifier) {
        assert !isClosed();
        typeBuffer.add(MessageType.RECORD_START);
        valueBuffer.add(identifier);
    }

    @Override
    public void endRecord() {
        assert !isClosed();
        typeBuffer.add(MessageType.RECORD_END);
    }

    @Override
    public void startEntity(final String name) {
        assert !isClosed();
        typeBuffer.add(MessageType.ENTITY_START);
        valueBuffer.add(name);
    }

    @Override
    public void endEntity() {
        assert !isClosed();
        typeBuffer.add(MessageType.ENTITY_END);
    }

    @Override
    public void literal(final String name, final String value) {
        assert !isClosed();
        typeBuffer.add(MessageType.LITERAL);
        valueBuffer.add(name);
        valueBuffer.add(value);
    }

    @Override
    protected void onResetStream() {
        clear();
    }

}