class RuboCop::Cop::Style::TrailingUnderscoreVariable

def allow_named_underscore_variables
  @allow_named_underscore_variables ||=
    cop_config['AllowNamedUnderscoreVariables']
end

def autocorrect(node)
  lambda do |corrector|
    range = unneeded_range(node)
    corrector.remove(range) if range
  end
end

def find_first_offense(variables)
  first_offense = nil
  variables.reverse_each do |variable|
    var, = *variable
    var, = *var
    if allow_named_underscore_variables
      break unless var == :_
    else
      break unless var.to_s.start_with?(UNDERSCORE)
    end
    first_offense = variable
  end
  return nil if first_offense.nil?
  first_offense_index = variables.index(first_offense)
  0.upto(first_offense_index - 1).each do |index|
    return nil if variables[index].splat_type?
  end
  first_offense
end

def on_masgn(node)
  return unless (range = unneeded_range(node))
  good_code = node.source
  offset = range.begin_pos - node.source_range.begin_pos
  good_code[offset, range.size] = ''
  add_offense(node, range, format(MSG, good_code))
end

def unneeded_range(node)
  left, right = *node
  variables = *left
  first_offense = find_first_offense(variables)
  return unless first_offense
  end_position =
    if first_offense.source_range == variables.first.source_range
      right.source_range.begin_pos
    else
      node.loc.operator.begin_pos
    end
  range =
    Parser::Source::Range.new(node.source_range.source_buffer,
                              first_offense.source_range.begin_pos,
                              end_position)
  range_with_surrounding_space(range, :right)
end