module TinyState
  class StateMachine
    attr_reader :attribute

    def initialize(attribute:)
      @attribute = attribute
      @states = Set.new
      @events = {}
    end

    def states = @states.to_a

    def events = @events.keys

    def inspect
      "#<#{self.class}:#{"%#016x" % (object_id << 1)} :#{attribute}, states: #{states}, events: #{events}>"
    end

    private

    def state(state)
      @states.merge([*state].map(&:to_sym))
    end

    def event(name, klass)
      @events[name.to_sym] = klass
    end

    def register_events(klass)
      attribute = @attribute

      @events.each do |name, event_klass|
        klass.define_method(:"#{name}!") do
          event_klass.new(resource: self, attribute:).transition!
        end

        klass.define_method(:"#{name}?") do
          event_klass.new(resource: self, attribute:).transition?
        end
      end
    end
  end
end