Proof of concept for calculating cron job times

cron.rb

#!/usr/bin/env ruby

# Calculate the next match for cron conditions (secs).
# Numbers > 60 mean the match is in the next minute.
#
# Arbitrary conditions:
# just take the minimum of all the individual ones.


# 60 secs / min
MAX = 60


# Next match for a range
def next_range(current, range)
  case
  when current < range.first
    range.first
  when current > range.last
    60 + range.first
  when current > range.first && current < range.last
    current + 1
  else
    raise "unexpected"
  end
end

# Next match for a modulo condition
def next_mod(current, operand)
  ((current / operand).floor + 1) * operand
end

# Next match for an exact condition
def next_exact(current, exact)
  if current < exact
    exact
  else
    60 + exact
  end
end


require "minitest/autorun"

class CronTest < MiniTest::Test
  def test_range
    assert_equal 20, next_range(10, 20..30)
    assert_equal 80, next_range(50, 20..30)
    assert_equal 25, next_range(24, 20..30)
  end

  def test_mod
    assert_equal 10, next_mod(0, 10)
    assert_equal 10, next_mod(5, 10)
    assert_equal 60, next_mod(59, 10)
  end

  def test_exact
    assert_equal 10, next_exact(0, 10)
    assert_equal 70, next_exact(11, 10)
  end
end

nice! I can't think of anything that won't work right now - Mind if I share it?