/*
 * 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.hyracks.control.nc.dataset;

import java.nio.ByteBuffer;
import java.util.concurrent.Executor;
import java.util.logging.Level;
import java.util.logging.Logger;

import edu.uci.ics.hyracks.api.comm.IFrameWriter;
import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
import edu.uci.ics.hyracks.comm.channels.NetworkOutputChannel;

public class DatasetPartitionReader {
    private static final Logger LOGGER = Logger.getLogger(DatasetPartitionReader.class.getName());

    private final DatasetMemoryManager datasetMemoryManager;

    private final Executor executor;

    private final ResultState resultState;

    public DatasetPartitionReader(DatasetMemoryManager datasetMemoryManager, Executor executor, ResultState resultState) {
        this.datasetMemoryManager = datasetMemoryManager;
        this.executor = executor;
        this.resultState = resultState;
    }

    public void writeTo(final IFrameWriter writer) {
        executor.execute(new Runnable() {
            @Override
            public void run() {
                NetworkOutputChannel channel = (NetworkOutputChannel) writer;
                channel.setFrameSize(resultState.getFrameSize());
                try {
                    resultState.readOpen();
                    channel.open();
                    try {
                        long offset = 0;
                        ByteBuffer buffer = ByteBuffer.allocate(resultState.getFrameSize());
                        while (true) {
                            buffer.clear();
                            long size = read(offset, buffer);
                            if (size <= 0) {
                                break;
                            } else if (size < buffer.limit()) {
                                throw new HyracksDataException("Premature end of file - readSize: " + size
                                        + " buffer limit: " + buffer.limit());
                            }
                            offset += size;
                            buffer.flip();
                            channel.nextFrame(buffer);
                        }
                    } finally {
                        channel.close();
                        resultState.readClose();
                    }
                } catch (HyracksDataException e) {
                    throw new RuntimeException(e);
                }
                if (LOGGER.isLoggable(Level.INFO)) {
                    LOGGER.info("result reading successful(" + resultState.getResultSetPartitionId() + ")");
                }
            }

            private long read(long offset, ByteBuffer buffer) throws HyracksDataException {
                if (datasetMemoryManager == null) {
                    return resultState.read(offset, buffer);
                } else {
                    return resultState.read(datasetMemoryManager, offset, buffer);
                }
            }
        });
    }
}