class RuboCop::Cop::Rails::PluralizationGrammar

def autocorrect(node)
  lambda do |corrector|
    method_name = node.loc.selector.source
    corrector.replace(node.loc.selector, correct_method(method_name))
  end
end

def correct_method(method_name)
  if plural_method?(method_name)
    singularize(method_name)
  else
    pluralize(method_name)
  end
end

def duration_method?(method_name)
  SINGULAR_DURATION_METHODS.key?(method_name) ||
    PLURAL_DURATION_METHODS.key?(method_name)
end

def literal_number?(node)
  node && (node.int_type? || node.float_type?)
end

def message(node)
  number, = *node.receiver
  format(MSG, number: number,
              correct: correct_method(node.method_name.to_s))
end

def offense?(node)
  number, = *node.receiver
  singular_receiver?(number) && plural_method?(node.method_name) ||
    plural_receiver?(number) && singular_method?(node.method_name)
end

def on_send(node)
  return unless duration_method?(node.method_name)
  return unless literal_number?(node.receiver)
  return unless offense?(node)
  add_offense(node)
end

def plural_method?(method_name)
  method_name.to_s.end_with?('s')
end

def plural_receiver?(number)
  !singular_receiver?(number)
end

def pluralize(method_name)
  SINGULAR_DURATION_METHODS.fetch(method_name.to_sym).to_s
end

def singular_method?(method_name)
  !plural_method?(method_name)
end

def singular_receiver?(number)
  number.abs == 1
end

def singularize(method_name)
  PLURAL_DURATION_METHODS.fetch(method_name.to_sym).to_s
end