/*
 * Copyright 2009-2010 by The Regents of the University of California
 * 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 from
 *
 *     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 edu.uci.ics.pregelix.dataflow;

import java.nio.ByteBuffer;

import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
import edu.uci.ics.hyracks.api.dataflow.IOperatorNodePushable;
import edu.uci.ics.hyracks.api.dataflow.value.IRecordDescriptorProvider;
import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
import edu.uci.ics.hyracks.api.job.JobSpecification;
import edu.uci.ics.hyracks.dataflow.common.comm.io.ArrayTupleBuilder;
import edu.uci.ics.hyracks.dataflow.common.comm.io.FrameTupleAppender;
import edu.uci.ics.hyracks.dataflow.common.comm.util.FrameUtils;
import edu.uci.ics.hyracks.dataflow.std.base.AbstractSingleActivityOperatorDescriptor;
import edu.uci.ics.hyracks.dataflow.std.base.AbstractUnaryOutputSourceOperatorNodePushable;

public class EmptyTupleSourceOperatorDescriptor extends AbstractSingleActivityOperatorDescriptor {
    private static final long serialVersionUID = 1L;

    public EmptyTupleSourceOperatorDescriptor(JobSpecification spec) {
        super(spec, 0, 1);
    }

    @Override
    public IOperatorNodePushable createPushRuntime(final IHyracksTaskContext ctx,
            IRecordDescriptorProvider recordDescProvider, int partition, int nPartitions) throws HyracksDataException {
        return new AbstractUnaryOutputSourceOperatorNodePushable() {
            private ByteBuffer frame = ctx.allocateFrame();
            private ArrayTupleBuilder tb = new ArrayTupleBuilder(0);
            private FrameTupleAppender appender = new FrameTupleAppender(ctx.getFrameSize());

            @Override
            public void initialize() throws HyracksDataException {
                try {
                    writer.open();
                    appender.reset(frame, true);
                    if (!appender.append(tb.getFieldEndOffsets(), tb.getByteArray(), 0, tb.getSize())) {
                        throw new IllegalStateException();
                    }
                    FrameUtils.flushFrame(frame, writer);
                    writer.close();
                } catch (Exception e) {
                    throw new HyracksDataException(e);
                }
            }
        };
    }

}