require "asciimath2unitsml"

module Metanorma
  module Standoc
    module Cleanup
      def asciimath2mathml(text)
        text = text.gsub(%r{<stem type="AsciiMath">(.+?)</stem>}m) do
          "<amathstem>#{@c.decode($1)}</amathstem>"
        end
        text = Html2Doc.new({})
          .asciimath_to_mathml(text, ["<amathstem>", "</amathstem>"],
                               retain_asciimath: true)
        asciimath2mathml_wrap(text)
      end

      def asciimath2mathml_wrap(text)
        x = Nokogiri::XML(text)
        x.xpath("//*[local-name() = 'math'][not(parent::stem)]").each do |y|
          y.wrap("<stem type='MathML'></stem>")
        end
        x.xpath("//stem").each do |y|
          y.next_element&.name == "asciimath" and y << y.next_element
        end
        to_xml(x)
      end

      def xml_unescape_mathml(xml)
        return if xml.children.any?(&:element?)

        math = xml.text.gsub(/&lt;/, "<").gsub(/&gt;/, ">")
          .gsub(/&quot;/, '"').gsub(/&apos;/, "'").gsub(/&amp;/, "&")
          .gsub(/<[^: \r\n\t\/]+:/, "<").gsub(/<\/[^ \r\n\t:]+:/, "</")
        xml.children = math
      end

      MATHML_NS = "http://www.w3.org/1998/Math/MathML".freeze

      def mathml_preserve_space(math)
        math.xpath(".//m:mtext", "m" => MATHML_NS).each do |x|
          x.children = x.children.to_xml
            .gsub(/^\s/, "&#xA0;").gsub(/\s$/, "&#xA0;")
        end
      end

      def mathml_namespace(stem)
        stem.xpath("./math").each { |x| x.default_namespace = MATHML_NS }
      end

      def mathml_mi_italics
        { uppergreek: true, upperroman: true,
          lowergreek: true, lowerroman: true }
      end

      # presuppose multichar mi upright, singlechar mi MathML default italic
      def mathml_italicise(xml)
        xml.xpath(".//m:mi[not(ancestor::*[@mathvariant])]",
                  "m" => MATHML_NS).each do |i|
          char = @c.decode(i.text)
          i["mathvariant"] = "normal" if mi_italicise?(char)
        end
      end

      def mi_italicise?(char)
        return false if char.length > 1

        case char
        when /\p{Greek}/
          (/\p{Lower}/.match(char) && !mathml_mi_italics[:lowergreek]) ||
            (/\p{Upper}/.match(char) && !mathml_mi_italics[:uppergreek])
        when /\p{Latin}/
          (/\p{Lower}/.match(char) && !mathml_mi_italics[:lowerroman]) ||
            (/\p{Upper}/.match(char) && !mathml_mi_italics[:upperroman])
        else false
        end
      end

      UNITSML_NS = "https://schema.unitsml.org/unitsml/1.0".freeze

      def add_misc_container(xmldoc)
        unless ins = xmldoc.at("//metanorma-extension")
          a = xmldoc.at("//termdocsource") || xmldoc.at("//bibdata")
          a.next = "<metanorma-extension/>"
          ins = xmldoc.at("//metanorma-extension")
        end
        ins
      end

      def mathml_unitsML(xmldoc)
        return unless xmldoc.at(".//m:*", "m" => UNITSML_NS)

        misc = add_misc_container(xmldoc)
        unitsml = misc.add_child("<UnitsML xmlns='#{UNITSML_NS}'/>").first
        %w(Unit CountedItem Quantity Dimension Prefix).each do |t|
          gather_unitsml(unitsml, xmldoc, t)
        end
      end

      def gather_unitsml(unitsml, xmldoc, tag)
        tags = xmldoc.xpath(".//m:#{tag}", "m" => UNITSML_NS)
          .each_with_object({}) do |x, m|
          m[x["id"]] = x.remove
        end
        return if tags.empty?

        set = unitsml.add_child("<#{tag}Set/>").first
        tags.each_value { |v| set << v }
      end

      def asciimath2unitsml_options
        { multiplier: :space }
      end

      MATHVARIANT_OVERRIDE = {
        bold: { normal: "bold", italic: "bold-italic", fraktur: "bold-fraktur",
                script: "bold-script", "sans-serif": "bold-sans-serif",
                "sans-serif-italic": "sans-serif-bold-italic" },
        italic: { normal: "italic", bod: "bold-italic",
                  "sans-serif": "sans-serif-italic",
                  "bold-sans-serif": "sans-serif-bold-italic" },
        "bold-italic": { normal: "bold-italic", bold: "bold-italic",
                         italic: "bold-italic",
                         "sans-serif": "sans-serif-bold-italic",
                         "bold-sans-serif": "sans-serif-bold-italic",
                         "sans-serif-italic": "sans-serif-bold-italic" },
        fraktur: { normal: "fraktur", bold: "bold-fraktur" },
        "bold-fraktur": { normal: "bold-fraktur", fraktur: "bold-fraktur" },
        script: { normal: "script", bold: "bold-script" },
        "bold-script": { normal: "script", script: "bold-script" },
        "sans-serif": { normal: "sans-serif", bold: "bold-sans-serif",
                        italic: "sans-serif-italic",
                        "bold-italic": "sans-serif-bold-italic" },
        "bold-sans-serif": { normal: "bold-sans-serif", bold: "bold-sans-serif",
                             "sans-serif": "bold-sans-serif",
                             italic: "sans-serif-bold-italic",
                             "bold-italic": "sans-serif-bold-italic",
                             "sans-serif-italic": "sans-serif-bold-italic" },
        "sans-serif-italic": { normal: "sans-serif-italic",
                               italic: "sans-serif-italic",
                               "sans-serif": "sans-serif-italic",
                               bold: "sans-serif-bold-italic",
                               "bold-italic": "sans-serif-bold-italic",
                               "sans-serif-bold": "sans-serif-bold-italic" },
        "sans-serif-bold-italic": { normal: "sans-serif-bold-italic",
                                    italic: "sans-serif-bold-italic",
                                    "sans-serif": "sans-serif-bold-italic",
                                    "sans-serif-italic": "sans-serif-bold-italic",
                                    bold: "sans-serif-bold-italic",
                                    "bold-italic": "sans-serif-bold-italic",
                                    "sans-serif-bold": "sans-serif-bold-italic" },
      }.freeze

      def mathvariant_override(inner, outer)
        o = outer.to_sym
        i = inner.to_sym
        MATHVARIANT_OVERRIDE[o] or return inner
        MATHVARIANT_OVERRIDE[o][i] || inner
      end

      def mathml_mathvariant(math)
        math.xpath(".//*[@mathvariant]").each do |outer|
          outer.xpath(".//*[@mathvariant]").each do |inner|
            inner["mathvariant"] =
              mathvariant_override(inner["mathvariant"], outer["mathvariant"])
          end
        end
      end

      def mathml_cleanup(xmldoc)
        unitsml = Asciimath2UnitsML::Conv.new(asciimath2unitsml_options)
        xmldoc.xpath("//stem[@type = 'MathML']").each do |x|
          xml_unescape_mathml(x)
          mathml_namespace(x)
          mathml_preserve_space(x)
          unitsml.MathML2UnitsML(x)
          mathml_mathvariant(x)
          mathml_italicise(x)
        end
        mathml_unitsML(xmldoc)
      end
    end
  end
end