class RuboCop::Cop::Performance::ReverseFirst


array.last
array.last(5).reverse
# good
array.reverse.first
array.reverse.first(5)
# bad
@example
can be replaced by ‘last(n).reverse` and `last`.
Identifies places where `reverse.first(n)` and `reverse.first`

def build_good_method(node) 

def build_good_method(node)
  if node.arguments?
    "last(#{node.first_argument.source})#{node.loc.dot.source}reverse"
  else
    'last'
  end
end

def build_message(node, range) 

def build_message(node, range)
  good_method = build_good_method(node)
  bad_method = range.source
  format(MSG, good_method: good_method, bad_method: bad_method)
end

def correction_range(receiver, node) 

def correction_range(receiver, node)
  range_between(receiver.loc.selector.begin_pos, node.source_range.end_pos)
end

def on_send(node) 

def on_send(node)
  reverse_first_candidate?(node) do |receiver|
    range = correction_range(receiver, node)
    message = build_message(node, range)
    add_offense(range, message: message) do |corrector|
      replacement = build_good_method(node)
      corrector.replace(range, replacement)
    end
  end
end