module Util
  # A simple event registering/triggering module to mix into classes.
  # Events are stored in the `@events` ivar.
  module Eventable

    # Register a handler for the given event name.
    # The event name is the method name called on the handler object
    #
    #   obj.on(:foo , some_object_that_implements foo( whateverargs)
    #
    # @param [String, Symbol] name event name
    # @param [Object] object handling the event, ie implement the function name
    # @return handler
    def register_event(name, handler)
      event_table[name] << handler
      handler
    end

    def unregister_event(name, handler)
      event_table[name].delete handler
    end

    def event_table
      return @event_table if @event_table
      @event_table = Hash.new { |hash, key| hash[key] = [] }
    end

    # Trigger the given event name and passes all args to each handler
    # for this event.
    #
    #   obj.trigger(:foo)
    #   obj.trigger(:foo, 1, 2, 3)
    #
    # @param [String, Symbol] name event name to trigger
    def trigger(name, *args)
      event_table[name].each { |handler| handler.send( name.to_sym , *args) }
    end
  end
end
