class EcoRake
  module Options
    # Gathers all the option presets (`EcoRake::Options::Set`) defined.
    # It works at class level and does lazy loading.
    class Library
      extend RakeCommander::Base::ClassHelpers
      extend RakeCommander::Base::ClassAutoLoader

      class_resolver :item_class, EcoRake::Options::Set

      autoloads_children_of :item_class
      autoload_namespace_ignore "EcoRake::Options"

      class << self
        include Enumerable

        # Iterator
        def each(&block)
          return to_enum(:each) unless block_given?
          sets.values.each(&block)
        end

        # Retrieve an options set
        # @return [EcoRake::Options::Set] the class with that `name`
        def [](value)
          sets[to_name(value)]
        end

        # @return [Boolean]
        def set?(name)
          raise "Expected String or Symbol. Given: #{name.class}" unless name.respond_to?(:to_sym)
          sets.key?(name.to_sym)
        end

        # @return [Array<Symbol>] names list of all available option sets.
        def names
          setes.keys
        end

        # Add a new options set.
        # @note
        #   1. If it receives an `item_class` (`Class`) it just adds it in
        #   2. If it receives an object instance, it adds its class
        # @return [EcoRake::Options::Set] the class
        def add(options_set)
          klass = options_set.is_a?(Class)? options_set : options_set.class
          raise "Expecting #{item_class} child or instance. Given: #{klass}" unless klass <= item_class
          puts "Warning: redefining options set '#{set.name}'"               if self[options_set.name]
          sets[options_set.name] = klass
        end

        private

        def autoload_children
          super(self) do |instance|
            add(instance)
          end
        end

        # It loads pending children of `item_class` every time it's invoked.
        # @note if sets is used as unique access point, this should ensure all children are known/loaded.
        # @return [Hash] where `key` is option_set name and value is the `item_class` (i.e. EcoRake::Options::Set)
        def sets
          autoload_children
          @sets ||= {}
        end

        # To-name converter
        # @return [Symbol, NilClass]
        def to_name(value)
          case value
          when String, Symbol
            value.to_sym
          when item_class
            value.name
          end
        end
      end
    end
  end
end