# Perform a certain action on specified time (useful as an alarm clock).
function alarm {
  usage="usage: $(basename $0) HH[:MM[:SS]] [action]"
  default_action="mpc play"
  if [[ $# -lt 1 ]]; then
    print -- $usage
    return 1
  fi
  wtime=$1
  shift
  action="$default_action"
  if [[ $# -gt 0 ]]; then
    action="$@"
  fi
  wsplit=(${(s.:.)wtime})
  integer H=${wsplit[1]} M=${wsplit[2]:-0} S=${wsplit[3]:-0}
  if [[ $#wsplit > 3 || $H -ge 24 || $M -ge 60 || $S -ge 60 ]]; then 
    print -- $usage
    return 1
  fi
  dtime=$(date +%T)
  ds=(${(s.:.)dtime})
  integer CH=${ds[1]} CM=${ds[2]} CS=${ds[3]}
  (( sleeptime = ($H - $CH) * 3600 + ($M - $CM) * 60 + $S - $CS ))
  if (( $sleeptime < 0 )); then (( sleeptime = (24*3600) + $sleeptime )); fi
  sleep $sleeptime
  print -- "[$(red alarm) $(green $wtime)]: $action"
  if eval $action; then
    return 0
  fi
  return 1
}