# frozen_string_literal: true

module IEV
  module Converter
    class MathmlToAsciimath
      using DataConversions

      def self.convert(input)
        new.convert(input)
      end

      def convert(input)
        mathml_to_asciimath(input)
      end

      private

      def mathml_to_asciimath(input)
        # If given string does not include '<' (for elements) nor '&'
        # (for entities), then it's certain that it doesn't contain
        # any MathML or HTML formula.
        return input unless input&.match?(/<|&/)

        unless input.include?("<math>")
          return html_to_asciimath(input)
        end

        # puts "GOING TO MATHML MATH"
        # puts input
        to_asciimath = Nokogiri::HTML.fragment(input, "UTF-8")
        # to_asciimath.remove_namespaces!

        to_asciimath.css("math").each do |math_element|
          asciimath = Plurimath::Math.parse(
            text_to_asciimath(math_element.to_xml), :mathml
          ).to_asciimath.strip
          # puts"ASCIIMATH!!  #{asciimath}"

          if asciimath.empty?
            math_element.remove
          else
            math_element.replace "stem:[#{asciimath}]"
          end
        end

        html_to_asciimath(
          to_asciimath.children.to_s,
        )
      end

      def html_to_asciimath(input)
        return input if input.nil? || input.empty?

        to_asciimath = Nokogiri::HTML.fragment(input, "UTF-8")

        to_asciimath.css("i").each do |math_element|
          # puts "HTML MATH!!  #{math_element.to_xml}"
          # puts "HTML MATH!!  #{math_element.text}"
          decoded = text_to_asciimath(math_element.text)
          case decoded.length
          when 1..12
            # puts "(#{math_element.text} to => #{decoded})"
            math_element.replace "stem:[#{decoded}]"
          when 0
            math_element.remove
          else
            math_element.replace "_#{decoded}_"
          end
        end

        to_asciimath.css("sub").each do |math_element|
          case math_element.text.length
          when 0
            math_element.remove
          else
            math_element.replace "~#{text_to_asciimath(math_element.text)}~"
          end
        end

        to_asciimath.css("sup").each do |math_element|
          case math_element.text.length
          when 0
            math_element.remove
          else
            math_element.replace "^#{text_to_asciimath(math_element.text)}^"
          end
        end

        to_asciimath.css("ol").each do |element|
          element.css("li").each do |li|
            li.replace ". #{li.text}"
          end
        end

        to_asciimath.css("ul").each do |element|
          element.css("li").each do |li|
            li.replace "* #{li.text}"
          end
        end

        # Replace sans-serif font with monospace
        to_asciimath.css('font[style*="sans-serif"]').each do |x|
          x.replace "`#{x.text}`"
        end

        html_entities_to_stem(
          to_asciimath
            .children.to_s
            .gsub(/\]stem:\[/, "")
            .gsub(/<\/?[uo]l>/, ""),
        )
      end

      def text_to_asciimath(text)
        html_entities_to_asciimath(text.decode_html)
      end

      def html_entities_to_asciimath(input)
        input.gsub("&alpha;", "alpha").
          gsub("&beta;", "beta").
          gsub("&gamma;", "gamma").
          gsub("&Gamma;", "Gamma").
          gsub("&delta;", "delta").
          gsub("&Delta;", "Delta").
          gsub("&epsilon;", "epsilon").
          gsub("&varepsilon;", "varepsilon").
          gsub("&zeta;", "zeta").
          gsub("&eta;", "eta").
          gsub("&theta;", "theta").
          gsub("&Theta;", "Theta").
          gsub("&vartheta;", "vartheta").
          gsub("&iota;", "iota").
          gsub("&kappa;", "kappa").
          gsub("&lambda;", "lambda").
          gsub("&Lambda;", "Lambda").
          gsub("&mu;", "mu").
          gsub("&nu;", "nu").
          gsub("&xi;", "xi").
          gsub("&Xi;", "Xi").
          gsub("&pi;", "pi").
          gsub("&Pi;", "Pi").
          gsub("&rho;", "rho").
          gsub("&beta;", "beta").
          gsub("&sigma;", "sigma").
          gsub("&Sigma;", "Sigma").
          gsub("&tau;", "tau").
          gsub("&upsilon;", "upsilon").
          gsub("&phi;", "phi").
          gsub("&Phi;", "Phi").
          gsub("&varphi;", "varphi").
          gsub("&chi;", "chi").
          gsub("&psi;", "psi").
          gsub("&Psi;", "Psi").
          gsub("&omega;", "omega")
      end

      def html_entities_to_stem(input)
        input.gsub("&alpha;", "stem:[alpha]").
          gsub("&beta;", "stem:[beta]").
          gsub("&gamma;", "stem:[gamma]").
          gsub("&Gamma;", "stem:[Gamma]").
          gsub("&delta;", "stem:[delta]").
          gsub("&Delta;", "stem:[Delta]").
          gsub("&epsilon;", "stem:[epsilon]").
          gsub("&varepsilon;", "stem:[varepsilon]").
          gsub("&zeta;", "stem:[zeta]").
          gsub("&eta;", "stem:[eta]").
          gsub("&theta;", "stem:[theta]").
          gsub("&Theta;", "stem:[Theta]").
          gsub("&vartheta;", "stem:[vartheta]").
          gsub("&iota;", "stem:[iota]").
          gsub("&kappa;", "stem:[kappa]").
          gsub("&lambda;", "stem:[lambda]").
          gsub("&Lambda;", "stem:[Lambda]").
          gsub("&mu;", "stem:[mu]").
          gsub("&nu;", "stem:[nu]").
          gsub("&xi;", "stem:[xi]").
          gsub("&Xi;", "stem:[Xi]").
          gsub("&pi;", "stem:[pi]").
          gsub("&Pi;", "stem:[Pi]").
          gsub("&rho;", "stem:[rho]").
          gsub("&beta;", "stem:[beta]").
          gsub("&sigma;", "stem:[sigma]").
          gsub("&Sigma;", "stem:[Sigma]").
          gsub("&tau;", "stem:[tau]").
          gsub("&upsilon;", "stem:[upsilon]").
          gsub("&phi;", "stem:[phi]").
          gsub("&Phi;", "stem:[Phi]").
          gsub("&varphi;", "stem:[varphi]").
          gsub("&chi;", "stem:[chi]").
          gsub("&psi;", "stem:[psi]").
          gsub("&Psi;", "stem:[Psi]").
          gsub("&omega;", "stem:[omega]")
      end
    end
  end
end