#!/bin/bash

function helpexit() {
    echo "Simple Timer."
    echo '$PREFIX is printed before the time'
    echo '$POSTFIX is printed after the time'
    echo '$TIMERPID is a PID number. When the process ends, timer ends.'
    echo 'Reset timer with kill -10'
    echo '

# use cases:
#  timer | sleep 10
#
#  timer &
#  sleep 10; kill -10 %1; sleep 5; kill %1
#
#  PREFIX=$'"'"'\033[33;1m'"'"' POSTFIX=$'"'"'\033[0m'"'"' timer | sleep 5
#
#  sleep 4 &
#  p=$!
#  TIMERPID=$p timer &
#  sleep 10
'
    exit
}


for (( i=1; i<=$#; i++ )); do
  [[ "${!i}" = "--help" ]] && helpexit
  [[ "${!i}" = "-h" ]] && helpexit
done

function displaytime {
  local T=$1
  local D=$((T/60/60/24))
  local H=$((T/60/60%24))
  local M=$((T/60%60))
  local S=$((T%60))
  printf '\r%s[' $PREFIX
  (( $D > 0 )) && printf '%dd ' $D
  (( $T > 3599 )) && printf '%02d:' $H
  printf '%02d:%02d]%s\r' $M $S $POSTFIX
}

function finish_up {
  echo "Timer terminated" >&2
  displaytime "$SECONDS" >&2
  echo "" >&2
  exit
}

function reset {
  STARTED=$SECONDS
}

trap finish_up EXIT 9 15
trap reset 10

STARTED=$SECONDS
while true; do
  # Were in terminal
  if [[ -t 1 ]]; then printf '\033[s'; fi
  displaytime $(( SECONDS - STARTED )) >&2
  if [[ -t 1 ]]; then printf '\033[u'; fi
  # die if parent dies
  kill -0 $PPID 2>/dev/null || { exit; }
  # if stdout is pipe, print time there
  # if pipe dies, timer dies too
  if [[ ! -t 1 ]]; then displaytime "$SECONDS"; fi
  if [[ -n "$TIMERPID" ]]; then
    kill -0 "$TIMERPID" 2>/dev/null || { exit; }
  fi
  sleep 1
done