percentages

#!/bin/bash

get_fraction() {
    st=$(date --date "$1" +%s)
    en=$(date --date "$2" +%s)
    now=$(date +%s)
  
    total=$(( $en - $st ))
    already_done=$(( $now - $st ))
    passed=$(echo "$already_done * 100 / $total" | bc -l)
    onesec=$( echo "1/$total" | bc -l )
}

determine_auto_precision() {
    mapfile -t full_num <<<$(echo "$onesec" | bc -l | cut -d'.' -f2 | grep -o .) 
    for i in "${!full_num[@]}"; do
        if [[ ${full_num[i]} -ne 0 ]]; then 
			echo $i
			break
		fi
    done
}

main() {
    start_time=$(date +'%Y-%m-%d %H:%m:%S' -d "January 1")
    end_time=$(date +'%Y-%m-%d %H:%m:%S' -d "January 1 next year")
    precision="auto"
    format="%\n"
	for i in "$@"; do
	case $i in
        -s|--start)
        start_time=$2 
        shift
        shift
        ;;
        -e|--end)
        end_time=$2 
        shift
        shift
        ;;
        -p|--precision)
        precision=$2 
        shift
        shift
        ;;
        -f|--format)
        format=$2 
        shift
        shift
        ;;
        *)    
		;;
	esac
	done
	get_fraction "$start_time" "$end_time"
    [[ $precision == "auto" ]] && precision=$(determine_auto_precision)
	string=$(printf "%.${precision}f\n" $passed)
	echo -e -n "${string}${format}"
}

main "$@"