module Plum
  module EventEmitter
    # Registers an event handler to specified event. An event can have multiple handlers.
    # @param name [String] The name of event.
    # @yield Gives event-specific parameters.
    def on(name, &blk)
      (callbacks[name] ||= []) << blk
    end

    def callback(name, *args)
      (cbs = callbacks[name]) && cbs.each {|cb| cb.call(*args) }
    end

    private
    def callbacks
      @callbacks ||= {}
    end
  end
end