StreamFlattener.java

/*
 * Copyright 2016 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.mangling;

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;

/**
 * Flattens all entities in a stream by prefixing the literals with the entity
 * paths. The stream emitted by this module is guaranteed to not contain any
 * <i>start-entity</i> and <i>end-entity</i> events.
 * <p>
 * For example, take the following sequence of events:
 * <pre>{@literal
 * start-record "1"
 * literal "top-level": literal-value
 * start-entity "entity"
 * literal "nested": literal-value
 * end-entity
 * end-record
 * }</pre>
 *
 * These events are transformed by the {@code StreamFlattener} into the
 * following sequence of events:
 * <pre>{@literal
 * start-record "1"
 * literal "top-level": literal-value
 * literal "entity.nested": literal-value
 * end-record
 * }</pre>
 *
 * @author Christoph Böhme (rewrite)
 * @author Markus Michael Geipel
 * @see EntityPathTracker
 *
 */
@Description("flattens out entities in a stream by introducing dots in literal names")
@In(StreamReceiver.class)
@Out(StreamReceiver.class)
@FluxCommand("flatten")
public final class StreamFlattener extends DefaultStreamPipe<StreamReceiver> {

	public static final String DEFAULT_ENTITY_MARKER = ".";

	private final EntityPathTracker pathTracker = new EntityPathTracker();

	public StreamFlattener() {
		setEntityMarker(DEFAULT_ENTITY_MARKER);
	}

	public String getEntityMarker() {
		return pathTracker.getEntitySeparator();
	}

	public void setEntityMarker(final String entityMarker) {
		pathTracker.setEntitySeparator(entityMarker);
	}

	@Override
	public void startRecord(final String identifier) {
		assert !isClosed();
		pathTracker.startRecord(identifier);
		getReceiver().startRecord(identifier);
	}

	@Override
	public void endRecord() {
		assert !isClosed();
		pathTracker.endRecord();
		getReceiver().endRecord();
	}

	@Override
	public void startEntity(final String name) {
		assert !isClosed();
		pathTracker.startEntity(name);
	}

	@Override
	public void endEntity() {
		assert !isClosed();
		pathTracker.endEntity();
	}

	@Override
	public void literal(final String name, final String value) {
		assert !isClosed();
		getReceiver().literal(pathTracker.getCurrentPathWith(name), value);
	}

	public String getCurrentEntityName() {
		return pathTracker.getCurrentEntityName();
	}

	public String getCurrentPath() {
		return pathTracker.getCurrentPath();
	}

}