module MusicXML
  module Node
    # Parses a node to get out the child nodes and attributes
    class Parser

      attr_reader :config, :node, :parsed

      # Store the given options and build a hash of the parsed nodes
      def initialize(args = {})
        @config = args[:config]
        @node   = args[:node]
        @parsed = {}
      end

      # Loop through each of the configured parsing options and store them
      def parse
        %w[plural_attrs plural_nodes singular_attrs singular_nodes properties].each do |method_name|
          config.send(method_name).each(&method(method_name))
        end
        parsed
      end

      private

      def find_class(name)
        ::MusicXML::Node.registry[name]
      end

      def plural_attrs(name)
        attr_nodes = node.search(symbol_to_node(name))
        set(name, attr_nodes.any? ? attr_nodes.map(&:content) : [])
      end

      def plural_nodes(name)
        clazz = find_class(name)
        node_list = node.search(symbol_to_node(name)).map do |child_node|
          clazz.new(child_node)
        end
        set(name, node_list.any? ? node_list : [])
      end

      def properties(name)
        attr = node.attributes[symbol_to_node(name)]
        set(name, attr.nil? ? '' : attr.value)
      end

      def set(key, value)
        parsed[:"@#{key}"] = value
      end

      def singular_attrs(name)
        attr_node = node.at(symbol_to_node(name))
        set(name, attr_node.content) unless attr_node.nil?
      end

      def singular_nodes(name)
        found_node = node.at(symbol_to_node(name))
        set(name, find_class(name).new(found_node)) if found_node
      end

      def symbol_to_node(name)
        name.to_s.tr('_', '-')
      end
    end
  end
end