class ProgressBar
  module Components
    module Progressable
      DEFAULT_TOTAL              = 100
      DEFAULT_BEGINNING_POSITION = 0
      DEFAULT_SMOOTHING          = 0.1

      attr_reader               :total
      attr_reader               :progress
      attr_accessor             :starting_position
      attr_accessor             :running_average
      attr_accessor             :smoothing

      def initialize(options = {})
        self.total           = options.fetch(:total, DEFAULT_TOTAL)
        self.smoothing       = options[:smoothing] || DEFAULT_SMOOTHING

        start :at => DEFAULT_BEGINNING_POSITION
      end

      def start(options = {})
        self.running_average   = 0

        self.progress          = \
        self.starting_position = options[:at] || self.progress
      end

      def started?
        !!self.starting_position
      end

      def increment
        self.progress += 1 unless progress == total
      end

      def decrement
        self.progress -= 1 unless progress == 0
      end

      def reset
        start :at => self.starting_position
      end

      def progress=(new_progress)
        validate_progress(new_progress)

        @progress = new_progress

        update_running_average
      end

      def total=(new_total)
        validate_total(new_total)
        @total = new_total
      end

      def finish
        self.progress = self.total
      end

      def percentage_completed
        return 100 if total == 0
        return 0   if total.nil?

        # progress / total * 100
        #
        # Doing this way so we can avoid converting each
        # number to a float and then back to an integer.
        #
        (self.progress * 100 / total).to_i
      end

      def percentage_completed_with_precision
        format('%5.2f', (progress.to_f * 100.0 / total * 100.0).floor / 100.0)
      end

    private
      def validate_total(new_total)
        (progress.nil? || new_total.nil? || new_total >= progress) || raise("You can't set the item's total value to be less than the current progress.")
      end

      def validate_progress(new_progress)
        (total.nil? || new_progress <= total) || raise("You can't set the item's current value to be greater than the total.")
      end

      def progress_made
        started? ? self.progress - self.starting_position : 0
      end

      def update_running_average
        self.running_average = RunningAverageCalculator.calculate(self.running_average, self.progress, self.smoothing)
      end
    end
  end
end