#!/usr/bin/env bash
# Usage: /folderpath/Timer.sh n n
# Where n and n are numeric values expressed in seconds. The first n is the interval in seconds of how often you would like to see updates to the
# timer display.
#
# The second n is the duration in seconds you would like the timer to run before shutting off. This is for use as an event timer.
#
# Replace folderpath with the actual path of folder names leading to the scripts location.
#
# To stop the script at any point press a character key in Terminal. By doing this you can use the Timer script as a stop watch, just set a long
# enough duration to cover at least the event length you are attempting to time, and hit any letter, number, or punctuation key to stop timing 
# when the event is over. Adjust the Interval to the granularity of accuracy you need from the stop watch mode of operation.
#
# initialize variables
# elapsed Minutes
declare -i Minutes=0
# elapsed Seconds
declare -i Seconds=0
# Elapsed keeps track of how long the timer has been running.
declare -i Elapsed=0
# Duration is how long you want the timer to run in seconds. if Duration is blank (unspecified) set default interval of 300 seconds.
Duration=${2:-300}
# Number of seconds left before timer ends.
Remainder=$Duration
# number of seconds between timer display updates. if Interval is blank (unspecified) set default interval of one second
Interval=${1:-1}
# clear the screen to begin displaying timer output.
clear
# display timer output
echo "Elapsed Time: $Minutes Minutes $Seconds Seconds"
echo "$Interval Second Interval" # echo interval setting
# read timeout for any key of one second forces us to trim 1 second from the Interval for proper execution.
(( Interval -=1 ))
# if Duration is blank (unspecified)
if [[ "$Duration" == "" ]]
    then
           Duration=300 # set default interval of 300 seconds.
fi
# finish first timer display screen
echo "$Duration Duration" # echo Duration setting
echo "$Remainder Seconds Remaining"
echo "To exit timer press any letter, number, or punctuation key."
echo "Timer will then exit after the next interval expires."
# While elapsed time is less than the Duration setting do loop till done.
while [[ $Elapsed -lt $Duration ]]
  do
# take care of overrun condition when Duration is not evenly divisible by Interval, resulting in leftover seconds,
if [[ "$Remainder" -lt "$Interval" ]]
    then
            # sleep only the number of seconds left to satisfy Duration.
            sleep $Remainder
            # update Seconds to proper value
            Seconds=$(( $Seconds +$Remainder ))
            # clear the screen for last timer display
            clear
            # put up last timer display
            echo "Elapsed Time: $Minutes Minute $Seconds Seconds"
            echo "$(( $Interval +1 )) Second Interval" # echo interval setting
            echo "$Duration Seconds Duration" # echo Duration setting
            echo "0 Seconds Remaining"
            echo "Timer has expired."
            # we're done, so exit the script.
            exit
fi
# sleep for the interval specified if interval is 1 or greater
if [[ $Interval -ne 0 ]]
   then
           sleep "$Interval"
fi
# Increment Seconds and Elapsed by the Interval setting + the 1 second read timeout value.
  (( Seconds += Interval + 1 ))
  (( Elapsed += Interval + 1 ))
# if Seconds equals 60, or is greater than 60 seconds, trim 60 from Seconds value, and add one to Minutes value.
[[ $Seconds -ge 60 ]] && (( Minutes += 1 )) && (( Seconds -= 60 ))
# check to see how much time is left to run
Remainder=$(( $Duration -$Elapsed ))
# clear the screen between each timer update
clear
# Update the timer display to the current values
if [ $Minutes == 1 ]
   then 
           echo "Elapsed Time: $Minutes Minute $Seconds Seconds"
           echo "$(( $Interval +1 )) Second Interval" # echo interval setting
           echo "$Duration Seconds Duration" # echo Duration setting
           echo "$Remainder Seconds Remaining"
           if [[ $Remainder -ne 0 ]]
               then
                      echo "To exit timer press any letter, number, or punctuation key."
                      echo "Timer will then exit after the next interval expires."
               else
                      echo "Timer has expired."
           fi
   else
           echo "Elapsed Time: $Minutes Minutes $Seconds Seconds"
           echo "$(( $Interval +1 )) Second Interval" # echo interval setting
           echo "$Duration Seconds Duration" # echo Duration setting
           echo "$Remainder Seconds Remaining"
           if [[ $Remainder -ne 0 ]]
               then
                      echo "To exit timer press any letter, number, or punctuation key."
                      echo "Timer will then exit after the next interval expires."
               else
                      echo "Timer has expired."
           fi
fi
# check to see if the user wants to exit the script by polling for a key press.
read -t 1 -n 1 ExitFlag
# if a key was pressed, exit the script.
if [ "$ExitFlag" != "" ]
    then 
            exit
fi
done
exit