module Split
  module Helper
    def ab_test(experiment_name, *alternatives)
      begin
        experiment = Split::Experiment.find_or_create(experiment_name, *alternatives)
        if experiment.winner
          ret = experiment.winner.name
        else
          if forced_alternative = override(experiment.name, alternatives)
            ret = forced_alternative
          else
            begin_experiment(experiment, experiment.control.name) if exclude_visitor?

            if ab_user[experiment.key]
              ret = ab_user[experiment.key]
            else
              alternative = experiment.next_alternative
              alternative.increment_participation
              begin_experiment(experiment, alternative.name)
              ret = alternative.name
            end
          end
        end
      rescue Errno::ECONNREFUSED => e
        raise unless Split.configuration.db_failover
        Split.configuration.db_failover_on_db_error.call(e)
        ret = Hash === (a0 = alternatives.first) ? a0.keys.first : a0
      end
      if block_given?
        if defined?(capture) # a block in a rails view
          block = Proc.new { yield(ret) }
          concat(capture(ret, &block))
          false
        else
          yield(ret)
        end
      else
        ret
      end
    end

    def finished(experiment_name, options = {:reset => true})
      return if exclude_visitor?
      return unless (experiment = Split::Experiment.find(experiment_name))
      if alternative_name = ab_user[experiment.key]
        alternative = Split::Alternative.new(alternative_name, experiment_name)
        alternative.increment_completion
        session[:split].delete(experiment_name) if options[:reset]
      end
    rescue Errno::ECONNREFUSED => e
      raise unless Split.configuration.db_failover
      Split.configuration.db_failover_on_db_error.call(e)
    end

    def override(experiment_name, alternatives)
      params[experiment_name] if defined?(params) && alternatives.include?(params[experiment_name])
    end

    def begin_experiment(experiment, alternative_name)
      ab_user[experiment.key] = alternative_name
    end

    def ab_user
      session[:split] ||= {}
    end

    def exclude_visitor?
      is_robot? or is_ignored_ip_address?
    end

    def is_robot?
      request.user_agent =~ Split.configuration.robot_regex
    end

    def is_ignored_ip_address?
      if Split.configuration.ignore_ip_addresses.any?
        Split.configuration.ignore_ip_addresses.include?(request.ip)
      else
        false
      end
    end
  end
end