package org.apache.samoa.instances;

/*
 * #%L
 * SAMOA
 * %%
 * Copyright (C) 2014 - 2015 Apache Software Foundation
 * %%
 * 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.
 * #L%
 */


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;

import org.apache.avro.Schema;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.io.Decoder;
import org.apache.avro.io.DecoderFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Load Data from JSON Avro Stream and parse to corresponding Dense & Parse Instances
 * 
 *
 */
public class AvroJsonLoader extends AvroLoader {

	private static final long serialVersionUID = 1L;
	private static final Logger logger = LoggerFactory.getLogger(AvroJsonLoader.class);

	/** The Character reader for JSON read */
	protected Reader reader  = null;

	public AvroJsonLoader(InputStream inputStream, int classAttribute) {
		super(classAttribute);
		initializeSchema(inputStream);
	}

	/* (non-Javadoc)
	 * @see org.apache.samoa.instances.AvroLoader#initializeSchema(java.io.InputStream)
	 */
	@Override
	public void initializeSchema(InputStream inputStream)
	{
		String schemaString = null;
		try {
			this.reader = new BufferedReader(new InputStreamReader(inputStream));
			schemaString = ((BufferedReader)this.reader).readLine();
			this.schema = new Schema.Parser().parse(schemaString);
			this.datumReader = new GenericDatumReader<GenericRecord>(schema);
			this.instanceInformation = getHeader();
			this.isSparseData = isSparseData();

			if (classAttribute < 0) {
				this.instanceInformation.setClassIndex(this.instanceInformation.numAttributes() - 1);
			} else if (classAttribute > 0) {
				this.instanceInformation.setClassIndex(classAttribute - 1);
			}

		} catch (IOException ioException) {
			logger.error(AVRO_LOADER_SCHEMA_READ_ERROR+" : {}",ioException);
			throw new RuntimeException(AVRO_LOADER_SCHEMA_READ_ERROR+" : " + ioException);
		}
	}

	/* (non-Javadoc)
	 * @see org.apache.samoa.instances.AvroLoader#readInstance()
	 */
	@Override
	public Instance readInstance() {

		String line = null;
		Decoder decoder = null;
		GenericRecord record = null;

		try{
			while ((line = ((BufferedReader)reader).readLine()) != null) {
				if(line==null || line.trim().length()<=0)
					continue;

				decoder = DecoderFactory.get().jsonDecoder(schema, line);
				record  = datumReader.read(null, decoder);
				break;
			}
		} catch (IOException ioException) {
			logger.error(AVRO_LOADER_INSTANCE_READ_ERROR+" : {}",ioException);
			throw new RuntimeException(AVRO_LOADER_INSTANCE_READ_ERROR+" : " + ioException);
		}

		if(record==null)
		{
			closeReader();
			return null;
		}

		if(isSparseData)
			return readInstanceSparse(record);

		return readInstanceDense(record);
	}

	/**
	 * Close the Avro Data Stream
	 */
	private void closeReader()
	{
		if(reader !=null)
			try {
				reader.close();
			} catch (IOException ioException) {
				logger.error(AVRO_LOADER_INSTANCE_READ_ERROR+" : {}",ioException);
				throw new RuntimeException(AVRO_LOADER_INSTANCE_READ_ERROR+" : " + ioException);
			}
	}
}