/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.hcatalog.utils;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;

import org.apache.hcatalog.common.HCatException;
import org.apache.hcatalog.data.transfer.DataTransferFactory;
import org.apache.hcatalog.data.transfer.HCatReader;
import org.apache.hcatalog.data.transfer.ReadEntity;
import org.apache.hcatalog.data.transfer.ReaderContext;

public class DataReaderMaster {

	public static void main(String[] args) throws FileNotFoundException, IOException {

		// This config contains all the configuration that master node wants to provide
		// to the HCatalog.
		Properties externalConfigs = new Properties();
		externalConfigs.load(new FileReader(args[0]));
		Map<String,String> config = new HashMap<String, String>();
		
		for (Entry<Object, Object> kv : externalConfigs.entrySet()){
			config.put((String)kv.getKey(), (String)kv.getValue());
		}
		
		// This piece of code runs in master node and gets necessary context.
		ReaderContext context = runsInMaster(config);

		ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File(args[1])));
		oos.writeObject(context);
		oos.flush();
		oos.close();
		// Master node will serialize readercontext and will make it available  at slaves.
	}

	private static ReaderContext runsInMaster(Map<String,String> config) throws HCatException {

		ReadEntity.Builder builder = new ReadEntity.Builder();
		ReadEntity entity = builder.withTable(config.get("table")).build();
		HCatReader reader = DataTransferFactory.getHCatReader(entity, config);
		ReaderContext cntxt = reader.prepareRead();
		return cntxt;
	}
}