module MicroMicro
  module Parsers
    class ValueClassPatternParser
      # @see https://microformats.org/wiki/value-class-pattern#Basic_Parsing
      # @see https://microformats.org/wiki/value-class-pattern#Date_and_time_values
      HTML_ATTRIBUTES_MAP = {
        'alt'      => %w[area img],
        'value'    => %w[data],
        'title'    => %w[abbr],
        'datetime' => %w[del ins time]
      }.freeze

      # @param context [Nokogiri::XML::Element]
      # @param separator [String]
      def initialize(node, separator = '')
        @node = node
        @separator = separator
      end

      # @return [String, nil]
      def value
        @value ||= values.join(separator).strip if values.any?
      end

      # @return [Array<String>]
      def values
        @values ||= value_nodes.map { |value_node| self.class.value_from(value_node) }.select(&:present?)
      end

      # @param context [Nokogiri::XML::NodeSet, Nokogiri::XML::Element]
      # @param node_set [Nokogiri::XML::NodeSet]
      # @return [Nokogiri::XML::NodeSet]
      def self.nodes_from(context, node_set = Nokogiri::XML::NodeSet.new(context.document, []))
        context.each { |node| nodes_from(node, node_set) } if context.is_a?(Nokogiri::XML::NodeSet)

        if context.is_a?(Nokogiri::XML::Element) && !Document.ignore_node?(context)
          if value_class_node?(context) || value_title_node?(context)
            node_set << context
          else
            nodes_from(context.element_children, node_set)
          end
        end

        node_set
      end

      # @param node [Nokogiri::XML::Element]
      # @return [Boolean]
      def self.value_class_node?(node)
        node.classes.include?('value')
      end

      # @param node [Nokogiri::XML::Element]
      # @return [String, nil]
      def self.value_from(node)
        return node['title'] if value_title_node?(node)

        HTML_ATTRIBUTES_MAP.each do |attribute, names|
          return node[attribute] if names.include?(node.name) && node[attribute]
        end

        node.text
      end

      # @param node [Nokogiri::XML::Element]
      # @return [Boolean]
      def self.value_title_node?(node)
        node.classes.include?('value-title')
      end

      private

      attr_reader :node, :separator

      # @return [Nokogiri::XML::NodeSet]
      def value_nodes
        @value_nodes ||= self.class.nodes_from(node)
      end
    end
  end
end