text_transformer.rb

# frozen_string_literal: true

module Asciidoctor
  module PDF
    module TextTransformer
      XMLMarkupRx = /&#?[a-z\d]+;|</
      PCDATAFilterRx = /(&#?[a-z\d]+;|<[^>]+>)|([^&<]+)/
      TagFilterRx = /(<[^>]+>)|([^<]+)/
      ContiguousCharsRx = /\p{Graph}+/
      WordRx = /\p{Word}+/
      Hyphen = '-'
      SoftHyphen = ?\u00ad
      LowerAlphaChars = 'a-z'
      # NOTE: use more widely-supported ғ instead of ꜰ as replacement for F
      # NOTE: use more widely-supported ǫ instead of ꞯ as replacement for Q
      # NOTE: use more widely-supported s (lowercase latin "s") instead of ꜱ as replacement for S
      # NOTE: in small caps, x (lowercase latin "x") remains unchanged
      SmallCapsChars = 'ᴀʙᴄᴅᴇғɢʜɪᴊᴋʟᴍɴoᴘǫʀsᴛᴜᴠᴡxʏᴢ'

      def capitalize_words_pcdata string
        if XMLMarkupRx.match? string
          string.gsub(PCDATAFilterRx) { $2 ? (capitalize_words $2) : $1 }
        else
          capitalize_words string
        end
      end

      def capitalize_words string
        string.gsub(ContiguousCharsRx) { $&.capitalize }
      end

      def hyphenate_words_pcdata string, hyphenator
        if XMLMarkupRx.match? string
          string.gsub(PCDATAFilterRx) { $2 ? (hyphenate_words $2, hyphenator) : $1 }
        else
          hyphenate_words string, hyphenator
        end
      end

      def hyphenate_words string, hyphenator
        string.gsub(WordRx) { hyphenator.visualize $&, SoftHyphen }
      end

      def lowercase_pcdata string
        if string.include? '<'
          string.gsub(TagFilterRx) { $2 ? $2.downcase : $1 }
        else
          string.downcase
        end
      end

      def uppercase_pcdata string
        if XMLMarkupRx.match? string
          string.gsub(PCDATAFilterRx) { $2 ? $2.upcase : $1 }
        else
          string.upcase
        end
      end

      def smallcaps_pcdata string
        if XMLMarkupRx.match? string
          string.gsub(PCDATAFilterRx) { $2 ? (smallcaps $2) : $1 }
        else
          smallcaps string
        end
      end

      def smallcaps string
        string = string.unicode_normalize :nfd unless string.ascii_only?
        string.tr LowerAlphaChars, SmallCapsChars
      end

      # Apply the text transform to the specified text.
      #
      # Supported transform values are "uppercase", "lowercase", or "none" (passed
      # as either a String or a Symbol). When the uppercase transform is applied to
      # the text, it correctly uppercases visible text while leaving markup and
      # named character entities unchanged. The none transform returns the text
      # unmodified.
      #
      def transform_text text, transform
        case transform
        when :uppercase, 'uppercase'
          uppercase_pcdata text
        when :lowercase, 'lowercase'
          lowercase_pcdata text
        when :capitalize, 'capitalize'
          capitalize_words_pcdata text
        when :smallcaps, 'smallcaps'
          smallcaps_pcdata text
        else
          text
        end
      end
    end
  end
end