Filter.java

/*
 * 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.culturegraph.mf.metamorph;


import org.culturegraph.mf.flowcontrol.StreamBuffer;
import org.culturegraph.mf.framework.FluxCommand;
import org.culturegraph.mf.framework.StreamReceiver;
import org.culturegraph.mf.framework.annotations.Description;
import org.culturegraph.mf.framework.annotations.In;
import org.culturegraph.mf.framework.annotations.Out;
import org.culturegraph.mf.framework.helpers.DefaultStreamPipe;
import org.culturegraph.mf.javaintegration.SingleValue;

/**
 * Filters a stream based on a morph definition. A record is accepted if the
 * morph returns at least one non empty value.
 *
 * @author Markus Michael Geipel
 *
 */
@Description("Filters a stream based on a morph definition. A record is accepted if the morph returns at least one non empty value.")
@In(StreamReceiver.class)
@Out(StreamReceiver.class)
@FluxCommand("filter")
public final class Filter extends DefaultStreamPipe<StreamReceiver> {

	private final StreamBuffer buffer = new StreamBuffer();
	private final SingleValue singleValue = new SingleValue();
	private final Metamorph metamorph;

	public Filter(final String morphDef) {
		super();
		metamorph = new Metamorph(morphDef);
		metamorph.setReceiver(singleValue);
	}

	public Filter(final Metamorph metamorph) {
		super();
		this.metamorph = metamorph;
		metamorph.setReceiver(singleValue);
	}

	@Override
	protected void onSetReceiver() {
		buffer.setReceiver(getReceiver());
	}


	private void dispatch(){
		final String key = singleValue.getValue();
		if(!key.isEmpty()){
			buffer.replay();
		}
		buffer.clear();
	}

	@Override
	public void startRecord(final String identifier) {
		buffer.startRecord(identifier);
		metamorph.startRecord(identifier);
	}

	@Override
	public void endRecord() {
		buffer.endRecord();
		metamorph.endRecord();
		dispatch();
	}

	@Override
	public void startEntity(final String name) {
		buffer.startEntity(name);
		metamorph.startEntity(name);
	}

	@Override
	public void endEntity() {
		buffer.endEntity();
		metamorph.endEntity();
	}

	@Override
	public void literal(final String name, final String value) {
		buffer.literal(name, value);
		metamorph.literal(name, value);
	}

	@Override
	protected void onResetStream() {
		buffer.clear();
		metamorph.resetStream();
	}

	@Override
	protected void onCloseStream() {
		buffer.clear();
		metamorph.closeStream();
	}
}