tracks/app/controllers/recurring_todos/form_helper.rb

module RecurringTodos
  class FormHelper
    def initialize(recurring_todo)
      @recurring_todo = recurring_todo

      @method_map = {
        # delegate daily_xxx to daily_pattern.xxx
        "daily"   => { prefix: "",    method: daily_pattern },
        "weekly"  => { prefix: "",    method: weekly_pattern },
        "monthly" => { prefix: "",    method: monthly_pattern },
        "yearly"  => { prefix: "",    method: yearly_pattern },
        # delegate on_xxx to weekly_pattern.on_xxx
        "on"      => { prefix: "on_", method: weekly_pattern }
      }
    end

    def create_pattern(pattern_class)
      pattern = pattern_class.new(@recurring_todo.user)
      pattern.build_from_recurring_todo(@recurring_todo)
      pattern
    end

    def daily_pattern
      @daily_pattern ||= create_pattern(DailyRecurrencePattern)
    end

    def weekly_pattern
      @weekly_pattern ||= create_pattern(WeeklyRecurrencePattern)
    end

    def monthly_pattern
      @monthly_pattern ||= create_pattern(MonthlyRecurrencePattern)
    end

    def yearly_pattern
      @yearly_pattern ||= create_pattern(YearlyRecurrencePattern)
    end

    def method_missing(method, *args)
      # delegate daily_xxx to daily_pattern, weekly_xxx to weekly_pattern, etc.
      if method.to_s =~ /^([^_]+)_(.+)$/
        return @method_map[$1][:method].send(@method_map[$1][:prefix] + $2, *args) unless @method_map[$1].nil?
      end

      # no match, let @recurring_todo handle it, or fail
      @recurring_todo.send(method, *args)
    end
  end
end