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/*
 * Copyright 2016 Christoph Böhme
 *
 * 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.triples;

import org.metafacture.formeta.parser.FormetaParser;
import org.metafacture.formeta.parser.PartialRecordEmitter;
import org.metafacture.framework.FluxCommand;
import org.metafacture.framework.StreamReceiver;
import org.metafacture.framework.annotations.Description;
import org.metafacture.framework.annotations.In;
import org.metafacture.framework.annotations.Out;
import org.metafacture.framework.helpers.DefaultObjectPipe;
import org.metafacture.framework.objects.Triple;
import org.metafacture.framework.objects.Triple.ObjectType;

/**
 * Converts triples into a stream.
 *
 * @author schaeferd
 *
 */
@Description("Converts a triple into a record stream")
@In(Triple.class)
@Out(StreamReceiver.class)
@FluxCommand("triples-to-stream")
public final class TriplesToStream extends
        DefaultObjectPipe {

    private final FormetaParser parser = new FormetaParser();
    private final PartialRecordEmitter emitter = new PartialRecordEmitter();

    /**
     * Creates an instance of {@link TriplesToStream}.
     */
    public TriplesToStream() {
        parser.setEmitter(emitter);
    }

    @Override
    public void process(final Triple triple) {
        getReceiver().startRecord(triple.getSubject());
        if (triple.getObjectType() == ObjectType.STRING) {
            getReceiver().literal(triple.getPredicate(), triple.getObject());
        }
        else if (triple.getObjectType() == ObjectType.ENTITY) {
            emitter.setDefaultName(triple.getPredicate());
            parser.parse(triple.getObject());
        }
        else {
            throw new UnsupportedOperationException(triple.getObjectType() + " can not yet be decoded");
        }
        getReceiver().endRecord();
    }

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

}