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.InputStream;
import java.util.ArrayList;
import java.util.List;

import org.apache.avro.Schema;
import org.apache.avro.Schema.Field;
import org.apache.avro.generic.GenericData.EnumSymbol;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.io.DatumReader;

/**
 * Load Data from Avro Stream and parse to corresponding Dense & Parse Instances
 * Abstract Class: Subclass this class for different types of Avro Encodings
 * 
 *
 */
public abstract class AvroLoader implements Loader {

	private static final long serialVersionUID = 1L;

	/** Representation of the Avro Schema for the Instances being read. Built from the first line in the data  */
	protected Schema schema = null;

	/**  Meta-data of the Instance */
	protected InstanceInformation instanceInformation;

	/** List of attributes in the data as read from the schema */
	protected List<Attribute> attributes;

	/** This variable is to check if the data stored is Sparse or Dense */
	protected boolean isSparseData;

	protected int classAttribute;

	/** Datum Reader for Avro Data*/
	public DatumReader<GenericRecord> datumReader = null;

	public AvroLoader(int classAttribute) {
		this.classAttribute = classAttribute;
		this.isSparseData = false;
	}

	/** Intialize Avro Schema, Meta Data, InstanceInformation from Input Avro Stream */
	public abstract void initializeSchema(InputStream inputStream);

	/** Read a single SAMOA Instance from Input Avro Stream */
	public abstract Instance readInstance();
	
	/**
	 * Method to read Dense Instances from Avro File
	 * @return Instance
	 */
	protected Instance readInstanceDense(GenericRecord record)
	{
		Instance instance = new DenseInstance(this.instanceInformation.numAttributes() + 1);
		int numAttribute = 0;

		for (Attribute attribute : attributes) {
			Object value = record.get(attribute.name);

			boolean isNumeric = attributes.get(numAttribute).isNumeric();
			boolean isNominal = attributes.get(numAttribute).isNominal();

			if(isNumeric)
			{
				if(value instanceof Double)	
					this.setDenseValue(instance, numAttribute, (double)value);
				else if (value instanceof Long)	
					this.setDenseValue(instance, numAttribute, (long)value);
				else if (value instanceof Integer)	
					this.setDenseValue(instance, numAttribute, (int)value);
				else
					throw new RuntimeException("Invalid data type in the Avro data for Numeric Type : "+attribute.name);
			}
			else if(isNominal)
			{
				double valueAttribute;

				if (!(value instanceof EnumSymbol))	
					throw new RuntimeException("Invalid data type in the Avro data for Nominal Type : "+attribute.name);

				EnumSymbol enumSymbolalue = (EnumSymbol)value;

				String stringValue = enumSymbolalue.toString();

				if (("?".equals(stringValue))||(stringValue==null)) {
					valueAttribute = Double.NaN; 
				} else {
					valueAttribute = this.instanceInformation.attribute(numAttribute).indexOfValue(stringValue);
				}

				this.setDenseValue(instance, numAttribute, valueAttribute);
			}
			numAttribute++;
		}

		return (numAttribute > 0) ? instance : null;

	}


	/**
	 * Sets a Dense Value in the corresponding attribute index
	 * @param instance is the Instance where values will be set
	 * @param numAttribute is the index of the attribute
	 * @param valueAttribute is the value of the attribute for this Instance
	 */

	private void setDenseValue(Instance instance, int numAttribute, double valueAttribute) {

		if (this.instanceInformation.classIndex() == numAttribute) 
			instance.setClassValue(valueAttribute);
		else 
			instance.setValue(numAttribute, valueAttribute);
	}

	/**
	 * Method to read Sparse Instances from Avro File
	 * @return Instance
	 */
	protected Instance readInstanceSparse(GenericRecord record) {

		Instance instance = new SparseInstance(1.0, null); 
		int numAttribute = -1;
		ArrayList<Double> attributeValues = new ArrayList<Double>();
		List<Integer> indexValues = new ArrayList<Integer>();

		for (Attribute attribute : attributes) {
			numAttribute++;
			Object value = record.get(attribute.name);

			boolean isNumeric = attributes.get(numAttribute).isNumeric();
			boolean isNominal = attributes.get(numAttribute).isNominal();

			/** If value is empty/null iterate to the next attribute.**/
			if(value==null)
				continue;

			if(isNumeric)
			{
				if(value instanceof Double)	
					this.setSparseValue(instance,  indexValues, attributeValues, numAttribute, (double)value);
				else if (value instanceof Long)	
					this.setSparseValue(instance,indexValues, attributeValues, numAttribute, (long)value);
				else if (value instanceof Integer)	
					this.setSparseValue(instance,indexValues, attributeValues, numAttribute, (int)value);
				else
					throw new RuntimeException(AVRO_LOADER_INVALID_TYPE_ERROR+" : "+attribute.name);
			}
			else if(isNominal)
			{
				double valueAttribute;

				if (!(value instanceof EnumSymbol))	
					throw new RuntimeException(AVRO_LOADER_INVALID_TYPE_ERROR+" : "+attribute.name);

				EnumSymbol enumSymbolalue = (EnumSymbol)value;

				String stringValue = enumSymbolalue.toString();

				if (("?".equals(stringValue))||(stringValue==null)) {
					valueAttribute = Double.NaN; 
				} else {
					valueAttribute = this.instanceInformation.attribute(numAttribute).indexOfValue(stringValue);
				}

				this.setSparseValue(instance, indexValues, attributeValues, numAttribute, valueAttribute);
			}
		}

		int[] arrayIndexValues = new int[attributeValues.size()];
		double[] arrayAttributeValues = new double[attributeValues.size()];
		
		for (int i = 0; i < arrayIndexValues.length; i++) {
			arrayIndexValues[i] = indexValues.get(i).intValue();
			arrayAttributeValues[i] = attributeValues.get(i).doubleValue();
		}
		
		instance.addSparseValues(arrayIndexValues, arrayAttributeValues,this.instanceInformation.numAttributes());
		return instance;

	}

	/**
	 * Sets a Sparse Value in the corresponding attribute index
	 * @param instance  is the Instance where values will be set
	 * @param indexValues is the list of Index values
	 * @param attributeValues is the list of Attribute values
	 * @param numAttribute is the index of the attribute
	 * @param valueAttribute is the value of the attribute for this Instance
	 */
	private void setSparseValue(Instance instance, List<Integer> indexValues, List<Double> attributeValues, int numAttribute, double valueAttribute) {
	
		if (this.instanceInformation.classIndex() == numAttribute) {
			instance.setClassValue(valueAttribute);
		} else {
			indexValues.add(numAttribute);
			attributeValues.add(valueAttribute);
		}
	}

	/**
	 * Builds the Meta Data of from the Avro Schema
	 * @return
	 */
	protected InstanceInformation getHeader() {

		String relation = schema.getName();
		attributes = new ArrayList<Attribute>();

		/** By Definition, the returned list is in the order of their positions. **/
		List<Schema.Field> fields = schema.getFields();

		for (Field field : fields) {
			Schema attributeSchema = field.schema();
			
			/** Currently SAMOA supports only NOMINAL & Numeric Types.**/
			if(attributeSchema.getType()==Schema.Type.ENUM)
			{
				List<String> attributeLabels = attributeSchema.getEnumSymbols();
				attributes.add(new Attribute(field.name(), attributeLabels));
			}
			else
				attributes.add(new Attribute(field.name()));
		}
		return new InstanceInformation(relation, attributes);
	}

	/**
	 * Identifies if the dataset is is Sparse or Dense
	 * @return boolean
	 */
	protected boolean isSparseData()
	{
		List<Schema.Field> fields = schema.getFields();
		for (Field field : fields) {
			Schema attributeSchema = field.schema(); 

			/** If even one attribute has a null union (nullable attribute) consider it as sparse data**/
			if(attributeSchema.getType()==Schema.Type.UNION)
			{
				List<Schema> unionTypes = attributeSchema.getTypes();
				for (Schema unionSchema : unionTypes) {
					if(unionSchema.getType()==Schema.Type.NULL)
						return true;
				}
			}

		}
		return false;
	}
	
	@Override
	public InstanceInformation getStructure() {
		return this.instanceInformation;
	}

	/** Error Messages to for all types of Avro Loaders */
	protected static final String AVRO_LOADER_INVALID_TYPE_ERROR = "Invalid data type in the Avro data"; 
	protected static final String AVRO_LOADER_SCHEMA_READ_ERROR = "Exception while reading the schema from Avro File"; 
	protected static final String AVRO_LOADER_INSTANCE_READ_ERROR = "Exception while reading the Instance from Avro File.";
}