rrrene/sparkr

# encoding: utf-8

module Sparkr
  class Sparkline
    TICKS = %w(▁ ▂ ▃ ▄ ▅ ▆ ▇ █)
    DEFAULT_SEPARATOR = ''

    def initialize(_numbers)
      if _numbers.empty?
        @ticks = []
      else
        @original_numbers = _numbers

        numbers  = normalize_numbers(_numbers)
        one_step = step_height(numbers)

        @ticks = numbers.map do |n|
          index = (n / one_step).to_i
          TICKS[index]
        end
      end
    end

    # Formats all the ticks in the Sparkline with a given block,
    # returns itself
    #
    # Example:
    #
    # Let's say you have a list of open and closed issues and want
    # to format it so the open ones are red and the closed ones are
    # green, so you can quickly see how you are doing. Let's further
    # suppose you use a gem that adds a #color method to String
    # for ANSI coloring.
    #
    #   list = [open_issue_count, closed_issue_count]
    #   sparkline = Sparkr::Sparkline.new(list)
    #   sparkline.format do |tick, count, index|
    #     if index == 0
    #       tick.color(:red)
    #     else
    #       tick.color(:green)
    #     end
    #   end
    #
    #   sparkline.to_s
    #   # => "▁█" (colored, which you can't see)
    #
    # @return [Sparkline] itself
    def format
      @ticks = @ticks.map.with_index do |tick, index|
        yield tick, @original_numbers[index], index
      end
      self
    end

    # Returns the normalized equivalent of a given list
    #
    #   normalize_numbers([3, 4, 7])
    #   # => [0, 1, 4]
    #
    # @return [Fixnum] the normalized equivalent of the given +_numbers+
    def normalize_numbers(_numbers)
      numbers = _numbers.map(&:to_i)
      min = numbers.min
      numbers.map do |n|
        n - min
      end
    end

    # @return [Float] the numerical "height" of a single bar "step"
    def step_height(_numbers)
      min, max = _numbers.minmax
      actual_height = max - min
      step = actual_height / steps.to_f
      if step == 0
        1
      else
        step
      end
    end

    # @return [Fixnum] the count of steps between the smallest and highest bar
    def steps
      TICKS.size - 1
    end

    # @param sep [String, nil] separator used to join the bars of the sparkline
    # @return [String] the sparkline, seperated by +sep+ (defaults to '')
    def to_s(sep = nil)
      @ticks.join(sep || DEFAULT_SEPARATOR)
    end
  end
end