ArtOfCode-/qpixel

module AdvertisementHelper
  RTL_BLOCK_START = 0x0590
  RTL_BLOCK_END = 0x06FF

  # Used to artificially fix RTL text in environments that are incapable of rendering mixed LTR and RTL text.
  # Parses the given string in sections of LTR and RTL; at each boundary between sections, dumps the section
  # into an output buffer - forwards if the section was LTR, reversed if the section was RTL - and clears the
  # scan buffer. This has the effect of reversing RTL sections in-place, which seems to correct their direction.
  #
  def do_rtl_witchcraft(str)
    chars = str.chars
    output_buffer = ''
    scan_buffer = []
    current_mode = rtl?(chars[0]) ? :rtl : :ltr
    chars.each.with_index do |c, i|
      new_mode = if c.match?(/\s/)
                   if chars[i - 1].present? && chars[i + 1].present? && rtl?(chars[i - 1]) && rtl?(chars[i + 1])
                     :rtl
                   else
                     :ltr
                   end
                 else
                   rtl?(c) ? :rtl : :ltr
                 end
      next if new_mode.nil?

      if new_mode != current_mode
        output_buffer += if current_mode == :rtl
                           scan_buffer.join.reverse
                         else
                           scan_buffer.join
                         end
        scan_buffer = []
      end
      current_mode = new_mode
      scan_buffer << c
    end

    output_buffer += if current_mode == :rtl
                       scan_buffer.join.reverse
                     else
                       scan_buffer.join
                     end
  end

  def rtl?(char)
    return false if char.nil?

    char.ord >= RTL_BLOCK_START && char.ord <= RTL_BLOCK_END
  end
end