module FollowEventTransitionMatcher

  class FollowEventTransition

    def initialize(event, options)
      @event = event
      @from = options[:from].is_a?(Array) ? options[:from] : [options[:from]]
      @to = options[:to]
    end

    def matches?(actual)
      actual.aasm_states.each do |state|
        o = build_type(actual, :state => state.name.to_sym)
        if @from.to_a.include? state.name.to_sym
          o.send(@event.to_sym)
          if !o.send("#{@to}?".to_sym)
            return false
          end
        else
          begin
            o.send(@event.to_sym)
            return false
          rescue AASM::InvalidTransition
          end
        end
      end
    end

    def build_type(klass, opts = {})
      Factory.build(klass.to_s.downcase.to_sym, opts)
    end

    def failure_message_for_should
      "Expected #{@event} to only allow transitions from #{@from} to #{@to}"
    end

    def failure_message_for_should_not
      "WARN: follow event transition shouldn't be used with the should_not syntax."
    end

  end

  def follow_event_transition(event, opts = {})
    FollowEventTransition.new(event, opts)
  end

end