SyntaxSuggest::AroundBlockScan#lookahead_balance_one_line

# File tmp/rubies/ruby-3.4.1/lib/syntax_suggest/around_block_scan.rb, line 141
def lookahead_balance_one_line
  kw_count = 0
  end_count = 0
  lines.each do |line|
    kw_count += 1 if line.is_kw?
    end_count += 1 if line.is_end?
  end

  return self if kw_count == end_count # nothing to balance

  @scanner.commit_if_changed # Rollback point if we don't find anything to optimize

  # Try to eat up empty lines
  @scanner.scan(
    up: ->(line, _, _) { line.hidden? || line.empty? },
    down: ->(line, _, _) { line.hidden? || line.empty? }
  )

  # More ends than keywords, check if we can balance expanding up
  next_up = @scanner.next_up
  next_down = @scanner.next_down
  case end_count - kw_count
  when 1
    if next_up&.is_kw? && next_up.indent >= @target_indent
      @scanner.scan(
        up: ->(line, _, _) { line == next_up },
        down: ->(line, _, _) { false }
      )
      @scanner.commit_if_changed
    end
  when -1
    if next_down&.is_end? && next_down.indent >= @target_indent
      @scanner.scan(
        up: ->(line, _, _) { false },
        down: ->(line, _, _) { line == next_down }
      )
      @scanner.commit_if_changed
    end
  end
  # Rollback any uncommitted changes
  @scanner.stash_changes

  self
end