class RuboCop::Cop::Style::PercentQLiterals

def autocorrect(node)
  src = node.loc.expression.source
  @corrections << lambda do |corrector|
    corrector.replace(node.loc.expression, corrected(src))
  end
end

def check(node, msg)
  src = node.loc.expression.source
  # Report offense only if changing case doesn't change semantics,
  # i.e., if the string would become dynamic or has special characters.
  return if node.children !=
    ProcessedSource.new(corrected(src)).ast.children
  add_offense(node, :begin, msg)
end

def corrected(src)
  src.sub(src[1], src[1].swapcase)
end

def on_percent_literal(node)
  if style == :lower_case_q
    if type(node) == '%Q'
      check(node,
            'Do not use `%Q` unless interpolation is needed.  ' \
            'Use `%q`.')
    end
  elsif type(node) == '%q'
    check(node, 'Use `%Q` instead of `%q`.')
  end
end

def on_str(node)
  process(node, '%Q', '%q')
end