#!/bin/sh

#===============================================================================
# scene-time
# create ffmpeg cutlist
#===============================================================================

# dependencies:
# ffmpeg awk head grep

#===============================================================================
# script usage
#===============================================================================

usage () {
# if argument passed to function echo it
[ -z "${1}" ] || echo "! ${1}"
# display help
echo "\
$(basename "$0") -i input -o output

-i input
-o output"
exit 2
}


#===============================================================================
# error messages
#===============================================================================

INVALID_OPT_ERR='Invalid option:'
REQ_ARG_ERR='requires an argument'
WRONG_ARGS_ERR='wrong number of arguments passed to script'


#===============================================================================
# check the number of arguments passed to the script
#===============================================================================

[ $# -gt 0 ] || usage "${WRONG_ARGS_ERR}"


#===============================================================================
# getopts check the options passed to the script
#===============================================================================

while getopts ':i:o:h' opt
do
  case ${opt} in
     i) input="${OPTARG}";;
     h) usage;;
     o) output="${OPTARG}";;
     \?) usage "${INVALID_OPT_ERR} ${OPTARG}" 1>&2;;
     :) usage "${INVALID_OPT_ERR} ${OPTARG} ${REQ_ARG_ERR}" 1>&2;;
  esac
done
shift $((OPTIND-1))


#===============================================================================
# variables
#===============================================================================

# get the input file name
input_nopath="${input##*/}"
input_name="${input_nopath%.*}"

# output file name
output_default="${input_name}-cutlist-$(date +"%Y-%m-%d-%H-%M-%S").txt"


#===============================================================================
# awk subtract 2nd line from first line - print start and duration
#===============================================================================

seconds () {
awk -F. 'NR > 1 {printf("%s%s%s\n"), prev, ",", $0-prev}; {prev = $0}' < "${input}" > "${output:=${output_default}}"
}

#===============================================================================
# convert sexagesimal to seconds - and subtract 2nd line from first line
# convert from seconds back to sexagesimal 
#===============================================================================

minutes () {
awk -F: 'NF==3 { printf("%s\n"), ($1 * 3600) + ($2 * 60) + $3 } NF==2 { print ($1 * 60) + $2 } NF==1 { printf("$s\n"), 0 + $1 }' < "${input}" \
| awk 'NR > 1 {printf("%s%s%s\n"), prev, "\n", $0-prev}; {prev = $0}' \
| awk -F. 'NF==1 { printf("%02d:%02d:%02d\n"), ($1 / 3600), ($1 % 3600 / 60), ($1 % 60) }\
NF==2 { printf("%02d:%02d:%02d.%s\n"), ($1 / 3600), ($1 % 3600 / 60), ($1 % 60), ($2) }' \
| awk '{ORS = NR%2 ? "," : "\n"} 1' > "${output:=${output_default}}"
}


#===============================================================================
# timecode regex
#===============================================================================

# grab the first line of the file
check=$(head -n1 "${input}")

# minutes - match 00:00:00.000
minutes_regex='^[0-9]{1,2}:[0-9]{2}:[0-9]{2}([.]{1}[0-9]{1,3})?$'

# seconds - match 00:00:00.000
seconds_regex='^[0-9]{1,8}([.]{1}[0-9]{1,3})?$'

# grep for the minutes
minutes=$(echo "${check}" | grep -E "${minutes_regex}")

# grep for the seconds
seconds=$(echo "${check}" | grep -E "${seconds_regex}")


#===============================================================================
# check timecode and run function
#===============================================================================

if [ -n "${minutes}" ]; then
  minutes
elif [ -n "${seconds}" ]; then
  seconds
else 
    usage
fi