ErrorHighlight::DefaultFormatter.message_for

# File tmp/rubies/ruby-4.1.0-preview1/lib/error_highlight/formatter.rb, line 5
def self.message_for(spot)
  # currently only a one-line code snippet is supported
  return "" unless spot[:first_lineno] == spot[:last_lineno]

  snippet      = spot[:snippet]
  first_column = spot[:first_column]
  last_column  = spot[:last_column]
  ellipsis     = "..."

  # truncate snippet to fit in the viewport
  if max_snippet_width && snippet.size > max_snippet_width
    available_width = max_snippet_width - ellipsis.size
    center          = first_column - max_snippet_width / 2

    visible_start  = last_column < available_width ? 0 : [center, 0].max
    visible_end    = visible_start + max_snippet_width
    visible_start  = snippet.size - max_snippet_width if visible_end > snippet.size

    prefix = visible_start.positive?    ? ellipsis : ""
    suffix = visible_end < snippet.size ? ellipsis : ""

    snippet = prefix + snippet[(visible_start + prefix.size)...(visible_end - suffix.size)] + suffix
    snippet << "\n" unless snippet.end_with?("\n")

    first_column -= visible_start
    last_column  = [last_column - visible_start, snippet.size - 1].min
  end

  indent = snippet[0...first_column].gsub(/[^\t]/, " ")
  marker = indent + "^" * (last_column - first_column)

  "\n\n#{ snippet }#{ marker }"
end