module Mabmapper
  module MabXml
    module QueryHelper

      def field(name_or_enum, options={})
        if name_or_enum.is_a?(String)
          query.add_field(name_or_enum, options)
        elsif name_or_enum.is_a?(Enumerable)
          name_or_enum.inject(query) { |q, name| q.add_field(name, options) }
        end
      end

      def subfield(name_or_enum)
        if name_or_enum.is_a?(String)
          query.add_subfield(name_or_enum)
        elsif name_or_enum.is_a?(Enumerable)
          name_or_enum.inject(query) { |q, name| q.add_subfield(name) }
        end
      end

      def get
        results = ResultSet.new

        query.xml.xpath(fields_xpath).each do |field_xml|
          name   = field_xml.attribute('tag').to_s
          field  = Field.new(name)

          field_xml.xpath(subfields_xpath).each do |subfield_xml|
            name  = subfield_xml.attribute('code').to_s
            value = subfield_xml.text.presence

            subfield = Subfield.new(name, value)
            field.add_subfield(subfield)
          end

          results.add_field(field)
        end

        results
      end

    private

      def query
        self.is_a?(Query) ? self : Query.new(@xml)
      end

      def fields_xpath
        options = query.fields.map do |f|
          name = f[:name]
          ind1 = indicator_xpath("ind1", f[:options][:ind1])
          ind2 = indicator_xpath("ind2", f[:options][:ind2])

          s = []
          s << "@tag='#{name}'"
          s << ind1 if ind1
          s << ind2 if ind2

          "(#{s.join(' and ')})"
        end.join(' or ')

        "/OAI-PMH/ListRecords/record/metadata/record/datafield[#{options}]"
      end

      def subfields_xpath
        global_negation = false

        options = query.subfields.map do |f|
          name = f[:name]

          negation = name.starts_with?('-') and name.length > 1
          name = negation ? name.slice(1..-1) : name
          global_negation = true if negation

          negation ? "not(@code='#{name}')" : "@code='#{name}'"
        end

        options = global_negation ? options.join(' and ') : options.join(' or ')

        options.present? ? "subfield[#{options}]" : "subfield"
      end

      def indicator_xpath(name, value)
        global_negation = false

        options = [*value].map do |value|
          if value
            negation = value.starts_with?('-') and value.length > 1
            global_negation = true if negation

            negation ? "not(@#{name}='#{value.slice(1..-1)}')" : "@#{name}='#{value}'"
          end
        end

        options = global_negation ? options.join(' and ') : options.join(' or ')

        options.present? ? "(#{options})" : nil
      end
    end
  end
end