module Asciidoctor
  module Ogc
    class Converter < Standoc::Converter
      def title_validate(root)
        nil
      end

      def content_validate(doc)
        super
        bibdata_validate(doc.root)
      end

      def bibdata_validate(doc)
        stage_validate(doc)
      end

      def stage_validate(xmldoc)
        stage = xmldoc&.at("//bibdata/status/stage")&.text
        %w(swg-draft oab-review public-rfc tc-vote
        published deprecated retired).include? stage or
        warn "Document Attributes: #{stage} is not a recognised status"
      end

      def section_validate(doc)
        sections_sequence_validate(doc.root)
      end

      STANDARDTYPE = %w{standard standard-with-suite abstract-specification
      community-standard profile}.freeze

      # spec of permissible section sequence
      # we skip normative references, it goes to end of list
      SEQ =
        [
          {
            msg: "Prefatory material must be followed by (clause) Scope",
            val: [{ tag: "clause", title: "Scope" }],
          },
          {
            msg: "Scope must be followed by Conformance",
            val: [{ tag: "clause", title: "Conformance" }],
          },
          {
            msg: "Normative References must be followed by "\
            "Terms and Definitions",
            val: [
              { tag: "terms", title: "Terms and definitions" },
              { tag: "clause", title: "Terms and definitions" },
              {
                tag: "terms",
                title: "Terms, definitions, symbols and abbreviated terms",
              },
              {
                tag: "clause",
                title: "Terms, definitions, symbols and abbreviated terms",
              },
            ],
          },
      ].freeze

      def seqcheck(names, msg, accepted)
        n = names.shift
        unless accepted.include? n
          warn "OGC style: #{msg}"
          names = []
        end
        names
      end

      def sections_sequence_validate(root)
        return unless STANDARDTYPE.include? root&.at("//bibdata/ext/doctype")&.text
        f = root.at("//sections").elements
        names = f.map { |s| { tag: s.name, title: s&.at("./title")&.text } }
        names = seqcheck(names, SEQ[0][:msg], SEQ[0][:val]) || return
        names = seqcheck(names, SEQ[1][:msg], SEQ[1][:val]) || return
        names = seqcheck(names, SEQ[2][:msg], SEQ[2][:val]) || return
        n = names.shift
        if !n.nil? && n[:tag] == "definitions"
          n = names.shift
        end
        unless n
          warn "OGC style: Document must contain at least one clause"
          return
        end
        root.at("//references | //clause[descendant::references][not(parent::clause)]") or
          seqcheck([{tag: "clause"}],
                   "Normative References are mandatory", [{tag: "references"}])
      end
    end
  end
end