angle_between_clock_hands

#! /usr/bin/env ruby

# given a time return the angle between analog clock hands at that time

puts "What time of day is it? (e.g 4:56)"

STDOUT.flush

raw_time_of_day = gets.chomp

begin
  raw_hours, minutes = *raw_time_of_day.match(/(\d{1,2}):(\d{2})/)[1..2].map(&:to_i)

  # and that's all the validation i'll do, should be fine, amiright........
  raise ArgumentError unless raw_hours && minutes

  # naive solution first?

  # get the angle relative to noon, which I'll place at 0 degrees

  # first, here is what a single minute represents in degrees
  each_minute = 360.0 / 60.0

  # and hours
  each_hour   = 360.0 / 12.0

  # and fractional hours
  each_minute_hour = 1.0 / 60.0

  # normalize hours
  hours = raw_hours == 12 ? 0 : raw_hours

  # get angles
  minutes_angle = each_minute * minutes
  hours_angle   = (hours * each_hour) + (each_minute_hour * minutes)

  # now return an angle
  puts "The angle is #{(hours_angle - minutes_angle).abs % 180} degrees"

rescue ArgumentError => e
  puts "Couldn't parse that time #{raw_time_of_day}"
  exit 1
end