1 files changed, 70 insertions, 0 deletions
diff --git a/lib/syntax_suggest/display_code_with_line_numbers.rb b/lib/syntax_suggest/display_code_with_line_numbers.rb
new file mode 100644
index 0000000000..a18d62e54b
--- /dev/null
+++ b/lib/syntax_suggest/display_code_with_line_numbers.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+module SyntaxSuggest
+  # Outputs code with highlighted lines
+  #
+  # Whatever is passed to this class will be rendered
+  # even if it is "marked invisible" any filtering of
+  # output should be done before calling this class.
+  #
+  #   DisplayCodeWithLineNumbers.new(
+  #     lines: lines,
+  #     highlight_lines: [lines[2], lines[3]]
+  #   ).call
+  #   # =>
+  #       1
+  #       2  def cat
+  #     > 3    Dir.chdir
+  #     > 4    end
+  #       5  end
+  #       6
+  class DisplayCodeWithLineNumbers
+    TERMINAL_HIGHLIGHT = "\e[1;3m" # Bold, italics
+    TERMINAL_END = "\e[0m"
+
+    def initialize(lines:, highlight_lines: [], terminal: false)
+      @lines = Array(lines).sort
+      @terminal = terminal
+      @highlight_line_hash = Array(highlight_lines).each_with_object({}) { |line, h| h[line] = true }
+      @digit_count = @lines.last&.line_number.to_s.length
+    end
+
+    def call
+      @lines.map do |line|
+        format_line(line)
+      end.join
+    end
+
+    private def format_line(code_line)
+      # Handle trailing slash lines
+      code_line.original.lines.map.with_index do |contents, i|
+        format(
+          empty: code_line.empty?,
+          number: (code_line.number + i).to_s,
+          contents: contents,
+          highlight: @highlight_line_hash[code_line]
+        )
+      end.join
+    end
+
+    private def format(contents:, number:, empty:, highlight: false)
+      string = +""
+      string << if highlight
+        "> "
+      else
+        "  "
+      end
+
+      string << number.rjust(@digit_count).to_s
+      if empty
+        string << contents
+      else
+        string << "  "
+        string << TERMINAL_HIGHLIGHT if @terminal && highlight
+        string << contents
+        string << TERMINAL_END if @terminal
+      end
+      string
+    end
+  end
+end