light_switch.rb

module Helpers
  class Range
    def self.merge_overlapping_ranges(ranges)
      ranges.sort_by(&:begin).inject([]) do |collection, range|
        if !collection.empty? && overlap?(collection.last, range)
          collection[0...-1] + [merge(collection.last, range)]
        else
          collection + [range]
        end
      end
    end

    def self.overlap?(range_1, range_2)
      range_1.include?(range_2.begin) || range_2.include?(range_1.begin)
    end

    def self.merge(range_1, range_2)
      [range_1.begin, range_2.begin].min..[range_1.end, range_2.end].max
    end
  end
end

class LightHub
  def initialize
    @time_periods = []
  end

  def record_runtime(range)
    @time_periods << range
  end

  def reset!
    @time_periods = []
  end

  def total_runtime
    ranges = Helpers::Range.merge_overlapping_ranges(@time_periods)
    ranges
      .inject([]) { |diff, range| diff << range.max - range.min }
      .sum
  end
end

class Assertions
  CHECKMARK = "\xE2\x9C\x94"
  CROSS = "\xE2\x9D\x8C"
  COLOURS = {
    green: "\033[0;32m",
    red: "\033[0;31m"
  }

  def self.assert_equal(expected, actual)
    result = expected == actual
    line_number =  caller_locations[0].lineno
    if result
      puts "#{COLOURS[:green]}#{CHECKMARK}  #{line_number}: Passed"
    else
      puts "#{COLOURS[:red]}#{CROSS} #{line_number}: Assertion Failed. \n\tExpected: #{expected} \n\tActual: #{actual}"
      exit(1)
    end
  end
end


light_hub = LightHub.new

light_hub.record_runtime(1..3)
Assertions.assert_equal(2, light_hub.total_runtime)

light_hub.record_runtime(2..3)
Assertions.assert_equal(2, light_hub.total_runtime)

light_hub.record_runtime(4..5)
Assertions.assert_equal(3, light_hub.total_runtime)

light_hub.record_runtime(2..8)
Assertions.assert_equal(7, light_hub.total_runtime)

light_hub.record_runtime(1..3)
Assertions.assert_equal(7, light_hub.total_runtime)

light_hub.reset!
Assertions.assert_equal(0, light_hub.total_runtime)