for (int i = 0; i < depth - 1; i++) {
String fileName = fileNames[i];
// todo: check before create
// todo: check correct module names
if ("".equals(fileName)) {
throw new IncorrectOperationException("File name cannot be empty");
}
char oldChar = fileName.charAt(0);
String dirName = fileName.replace(oldChar, Character.toUpperCase(oldChar));
PsiDirectory subDir = moduleDir.findSubdirectory(dirName);
moduleDir = subDir == null ? moduleDir.createSubdirectory(dirName) : subDir;