File renaming using Nashorn script

renamer.js

var FILE_PATTERNS = /^(Channel_Play_Success_Ratio|Video_Play_Success_Ratio|Login_Success_Ratio|Play_Success_Ratio).+\-1\.csv$/;

var Files = java.nio.file.Files;
var Paths = java.nio.file.Paths;

function printWithCarriageReturn(str) java.lang.System.out['print(String)'](str + '\r');

function throwError(msg) { throw new Error(msg); }; // Brackets are required

if (typeof $ARG === 'undefined' || $ARG.length === 0)
  print("Usage: jjs -scripting renamer.js -- FileOrFolder1 FileOrFolder2 ..");
else
{
  var inputPaths = $ARG.map(function(filePath) Paths.get(filePath));
  for (var i = 0; i < inputPaths.length; i++)
    if (!Files.exists(inputPaths[i]))
      throw new Error('"' + inputPaths[i] + '" does not exist');
  var noOfFilesRenamed = rename(inputPaths, 0);
  print(noOfFilesRenamed + ' file' + (noOfFilesRenamed === 1 ? '' : 's') + ' renamed.');
}

function rename(paths, noOfFilesRenamed)
{
  for (var i = 0; i < paths.length; i++)
  {
    var source = paths[i];
    
    if (Files.isDirectory(source))
    {
      var children = Java.from(source.toFile().listFiles() || throwError('Unable to read directory: ' + source))
                         .map(function(file) file.toPath());
      noOfFilesRenamed = rename(children, noOfFilesRenamed);
      continue;
    }
    
    var fileName = '' + source.fileName;
    if (!FILE_PATTERNS.test(fileName))
      continue;
    
    var newName = fileName.substring(0, fileName.length - 6 /* str before -1.csv */) + '.csv';
    var dest = source.resolveSibling(newName);
    
    Files.move(source, dest);
    
    noOfFilesRenamed++;
    
    if (noOfFilesRenamed % 300 === 0)
      printWithCarriageReturn(noOfFilesRenamed);
  }
  
  return noOfFilesRenamed;
}