#!/usr/bin/env ruby

require 'time'

def die(str)
  $stderr.puts str
  exit
end

def usage
  die "Usage: nap { for <float>[<h|m|s>] | until <date(1) parsable datestr> | cycles [<int>] }" +
    "\ne.g.  nap for 3h\n      nap until 10AM\n      nap cycles 4\n      " +
    "nap cycles 4+10 # 10 minutes to brush teeth"
end

def hourminutes(hours)
  wholes = hours.to_i
  minutes = (hours - hours.to_i) * 60

  "#{ wholes }:#{ ("0" + minutes.to_i.to_s)[-2..-1] }"
end

def kind_for(time)
  aliases = {'m' => 60, 'h' => 3600, 's' => 1}
  prefix  = aliases[(time.match('[hms]$') || ['s'])[0]]

  yield "# date format bogus" unless time.match(/^\d+(\.\d+)?([hms])?$/)

  "sudo rtcwake -m mem -t -s #{ time.to_f.*(prefix).to_i }"
end

def successfully(args)
  errors, pipe = IO.pipe
  IO.popen(args, err: pipe) do |p| p.read end.tap do
    pipe.close
    die errors.read unless $?.success?
  end
end

def kind_until(time)
  date = successfully(%w{date -d} + [time])
  secs = successfully(%w{date -d} + [time] + %w{+%s}).to_i

  hours = (((secs.to_i - Time.now.to_i) / 36) / 100.0)
  yield "# %s hours" % hourminutes(hours) if (0.40..60).include? hours
  yield "# #{ date }"

  "sudo rtcwake -m mem -t #{ secs }"
end

def kind_cycles(n = nil, &block)
  # Print time, if n = nil.
  # n = '1'    -> sleep one cycle + 14 minutes
  # n = '1+20' -> sleep one cylce + 14 minutes + 20 minutes to brush teeth

  gen = proc do |i, j|
    cycle = 3600 * 3 / 2
    tts   = 14 * 60 # a joke on Time To Live
    (Time.now + (cycle * i + tts + (j || 0) * 60)).strftime('%H:%M')
  end

  enough = 6
  times = (1..enough).map { |i| gen.call i }

  if n
    m, o = n.split('+').map(&:to_i)
    unless (1..enough).include? m
      yield "# only cycles 1 through #{ enough } are meant to be used"
    end

    kind_until(gen.call(m, o), &block)
  else
    yield "# according to http://sleepyti.me"
    yield "# you should wake up at:"
    yield("# " + times.join(', '))
  end
end

kind = ARGV[0]
timedescr = ARGV[1..-1]

if ARGV.length == 2
  usage if !kind.match(/^(until|for|cycles)$/)
elsif ARGV.length == 1
  usage if kind != 'cycles'
else
  usage
end

cmd = send(:"kind_#{ kind }", *timedescr) { |info| $stderr.puts info }
puts cmd if cmd