class ParticipationController < ApplicationController
      before_action :set_party, only: :create

      def create
        if current_user.age < 20
          redirect_to root_path and return
        elsif current_user.missing_last_train?
          redirect_to root_path and return
        end

        if current_user.friends.any? { |f| @party.members.include?(f) }
          @party.members << current_user
          redirect_to @party, notice: "ようこそ！"
        elsif choose
          @party.members << current_user
          redirect_to @party, notice: "ようこそ！"
        else
          redirect_to root_path, notice: "参加をあきらめました"
        end
      end

      private

      def choose(weight = 50)
        rand <= weight/100.0
      end
      # 省略
    end