class RuboCop::Cop::Lint::UnusedBlockArgument

def allow_unused_keyword_arguments?
  cop_config['AllowUnusedKeywordArguments']
end

def allowed_block?(variable)
  !variable.block_argument? ||
    (ignore_empty_blocks? && empty_block?(variable))
end

def allowed_keyword_argument?(variable)
  variable.keyword_argument? &&
    allow_unused_keyword_arguments?
end

def augment_message(message, variable)
  scope = variable.scope
  all_arguments = scope.variables.each_value.select(&:block_argument?)
  augmentation = if scope.node.lambda?
                   message_for_lambda(variable, all_arguments)
                 else
                   message_for_normal_block(variable, all_arguments)
                 end
  [message, augmentation].join(' ')
end

def check_argument(variable)
  return if allowed_block?(variable) ||
            allowed_keyword_argument?(variable)
  super
end

def define_method_call?(variable)
  call, = *variable.scope.node
  _, method, = *call
  method == :define_method
end

def empty_block?(variable)
  _send, _args, body = *variable.scope.node
  body.nil?
end

def ignore_empty_blocks?
  cop_config['IgnoreEmptyBlocks']
end

def message(variable)
  message = "Unused #{variable_type(variable)} - `#{variable.name}`."
  if variable.explicit_block_local_variable?
    message
  else
    augment_message(message, variable)
  end
end

def message_for_lambda(variable, all_arguments)
  message = message_for_underscore_prefix(variable)
  if all_arguments.none?(&:referenced?)
    proc_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, proc_message].compact.join(' ')
end

def message_for_normal_block(variable, all_arguments)
  if all_arguments.none?(&:referenced?) &&
     !define_method_call?(variable)
    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