class RuboCop::Cop::Lint::UnusedBlockArgument

def check_argument(variable)
  return unless variable.block_argument?
  if cop_config['IgnoreEmptyBlocks']
    _send, _args, body = *variable.scope.node
    return if body.nil?
  end
  super
end

def message(variable)
  message = String.new("Unused #{variable_type(variable)} - " \
                       "`#{variable.name}`.")
  return message if variable.explicit_block_local_variable?
  message << ' '
  scope = variable.scope
  all_arguments = scope.variables.each_value.select(&:block_argument?)
  message << if scope.node.lambda?
               message_for_lambda(variable, all_arguments)
             else
               message_for_normal_block(variable, all_arguments)
             end
  message
end

def message_for_lambda(variable, all_arguments)
  message = String.new(message_for_underscore_prefix(variable))
  if all_arguments.none?(&:referenced?)
    message << ' Also consider using a proc without arguments ' \
               'instead of a lambda if you want it ' \
                "to accept any arguments but don't care about them."
  end
  message
end

def message_for_normal_block(variable, all_arguments)
  if all_arguments.none?(&:referenced?)
    if all_arguments.count > 1
      "You can omit all the arguments if you don't care about them."
    else
      "You can omit the argument if you don't care about it."
    end
  else
    message_for_underscore_prefix(variable)
  end
end

def message_for_underscore_prefix(variable)
  "If it's necessary, use `_` or `_#{variable.name}` " \
  "as an argument name to indicate that it won't be used."
end

def variable_type(variable)
  if variable.explicit_block_local_variable?
    'block local variable'
  else
    'block argument'
  end
end