class RuboCop::Cop::Style::NegatedIf

def autocorrect(node)
  lambda do |corrector|
    condition, _body, _rest = *node
    # look inside parentheses around the condition
    condition = condition.children.first while condition.type == :begin
    # unwrap the negated portion of the condition (a send node)
    pos_condition, _method, = *condition
    corrector.replace(
      node.loc.keyword,
      node.loc.keyword.is?('if') ? 'unless' : 'if'
    )
    corrector.replace(condition.loc.expression,
                      pos_condition.loc.expression.source)
  end
end

def message(node)
  if node.loc.keyword.is?('if')
    format(MSG, 'unless', 'if')
  else
    format(MSG, 'if', 'unless')
  end
end

def on_if(node)
  return unless node.loc.respond_to?(:keyword)
  return if node.loc.keyword.is?('elsif')
  check_negative_conditional(node)
end