/*
 * 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.hadoop.chukwa;

import java.io.IOException;

import org.apache.pig.EvalFunc;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.impl.logicalLayer.schema.Schema;

/**
 * string.PARSEDOUBLE implements a binding to the Java method
 * {@link java.lang.Double#parseDouble(String)}
 * 
 * <dl>
 * <dt><b>Parameters:</b></dt>
 * <dd><code>strtoconvert</code> - <code>chararray</code>
 * 
 * <dt><b>Return Value:</b></dt>
 * <dd><code>double</code> parsed value</dd>
 * 
 * <dt><b>Return Schema:</b></dt>
 * <dd>parselong: double</dd>
 * 
 * <dt><b>Example:</b></dt>
 * <dd><code>
 * register string.jar;<br/>
 * A = load 'mydata' using PigStorage() as ( stringnumber: chararray );<br/>
 * B = foreach A generate stringnumber, org.apache.hadoop.chukwa.PARSEDOUBLE(stringnumber));
 * </code></dd>
 * </dl>
 * 
 */
public class PARSEDOUBLE extends EvalFunc<Double> {
  
  public Double exec(Tuple input) throws IOException {
    if (input == null || input.size() < 1)
      return null;
    try {
      String strtoconvert = input.get(0).toString();
      Double number = Double.parseDouble(strtoconvert);

      return number;
    } catch (Exception e) {
      return null;
    }
  }

  @Override
  public Schema outputSchema(Schema input) {
    Schema schema = null;
    try {
      schema = new Schema(new Schema.FieldSchema(input.getField(0).alias, DataType.DOUBLE));
    } catch (FrontendException e) {
      schema = new Schema(new Schema.FieldSchema(getSchemaName("parseDouble", input),
          DataType.DOUBLE));
    }
    return schema;
  }
}