class RuboCop::Cop::Style::MethodDefParentheses

def arguments_without_parentheses?(node)
  node.arguments? && !parentheses?(node.arguments)
end

def autocorrect(node)
  lambda do |corrector|
    if node.args_type?
      # offense is registered on args node when parentheses are unwanted
      corrector.replace(node.loc.begin, ' ')
      corrector.remove(node.loc.end)
    else
      args_expr = node.arguments.source_range
      args_with_space = range_with_surrounding_space(args_expr, :left)
      just_space = range_between(args_with_space.begin_pos,
                                 args_expr.begin_pos)
      corrector.replace(just_space, '(')
      corrector.insert_after(args_expr, ')')
    end
  end
end

def missing_parentheses(node)
  add_offense(node, node.arguments.source_range, MSG_MISSING) do
    unexpected_style_detected(:require_no_parentheses)
  end
end

def on_def(node)
  args = node.arguments
  if require_parentheses?(args)
    if arguments_without_parentheses?(node)
      missing_parentheses(node)
    else
      correct_style_detected
    end
  elsif parentheses?(args)
    unwanted_parentheses(args)
  else
    correct_style_detected
  end
end

def require_parentheses?(args)
  style == :require_parentheses ||
    (style == :require_no_parentheses_except_multiline &&
     args.multiline?)
end

def unwanted_parentheses(args)
  add_offense(args, :expression, MSG_PRESENT) do
    unexpected_style_detected(:require_parentheses)
  end
end