# 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?(/<|&/)

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

        # 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(%r{</?[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