/**                                                                                                                                                                                
 * 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. See accompanying                                                                                                                 
 * LICENSE file.                                                                                                                                                                   
 */

package com.yahoo.ycsb.generator;

import java.io.FileReader;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;

/**
 * A generator, whose sequence is the lines of a file.
 */
public class FileGenerator extends Generator<String>
{
	private final String filename;
	private String current;
	private BufferedReader reader;

	/**
	 * Create a FileGenerator with the given file.
	 * @param _filename The file to read lines from.
	 */
	public FileGenerator(String _filename) 
	{
	  filename = _filename;
	  reloadFile();
	}

	/**
	 * Return the next string of the sequence, ie the next line of the file.
	 */
	@Override
  public synchronized String nextValue()
	{
		try {
			return current = reader.readLine();
		} catch(IOException e) {
		  throw new RuntimeException(e);		
		}
	}

	/**
	 * Return the previous read line.
	 */
	@Override
  public String lastValue()
	{
		return current;
	}

	/**
	 * Reopen the file to reuse values.
	 */
	public synchronized void reloadFile() {
	  try (Reader r = reader) {
			System.err.println("Reload " + filename);
			reader = new BufferedReader(new FileReader(filename));
	  } catch (IOException e) {
	    throw new RuntimeException(e);
	  }
	}
}
