#!/bin/sh


#===============================================================================
# trim-remote
# trim a remote video clip with millisecond accuracy
#===============================================================================


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

usage () {
# if argument passed to function echo it
[ -z "${1}" ] || echo "! ${1}"
# display help
echo "\
# trim a remote video clip with millisecond accuracy
https://trac.ffmpeg.org/wiki/Seeking

$(basename "$0") -s 00:00:00.000 -i url -t 00:00:00.000 -o output
-s 00:00:00.000 : start time
-i url
-t 00:00:00.000 : number of seconds after start time
-o output.(mp4|webm|aac|mp3|wav|ogg) : optional argument 
# if option not provided defaults input-name-[start end].mp4"
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 number of aruments passed to script
#===============================================================================

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


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

while getopts ':s:i:t:o:h' opt
do
  case ${opt} in
     s) start="${OPTARG}";;
     i) input="${OPTARG}";;
     t) end="${OPTARG}";;
     h) usage;;
     o) outfile="${OPTARG}";;
     \?) usage "${INVALID_OPT_ERR} ${OPTARG}" 1>&2;;
     :) usage "${INVALID_OPT_ERR} ${OPTARG} ${REQ_ARG_ERR}" 1>&2;;
  esac
done
shift $((OPTIND-1))


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

# yt-dlp url
url=$(yt-dlp -i -f b -g --no-playlist --print '%(title)s' "${input}")

# check number of stream links
streamcount=$(echo "${url}" | awk '/^https?:\/\// {count++} END{ print count }')
urllist=$(echo "${url}" | awk '/^https?:\/\// { print $0 }')

# awk convert start and end time from sexagesimal time to seconds
# add the start and end time to get the endpoint and convert from seconds back to sexagesimal time
endtime=$(printf "%s %s\n" "${start}" "${end}" \
| awk '
        {
          start = $1
          end = $2
          if (start ~ /:/) {
            split(start, t, ":")
            sseconds = (t[1] * 3600) + (t[2] * 60) + t[3] 
          }
          if (end ~ /:/) {
            split(end, t, ":")
            eseconds = (t[1] * 3600) + (t[2] * 60) + t[3] 
          }
          duration = eseconds + sseconds
          printf("%s\n"), duration
     }' \
| 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) }'
)

# defaults for variables if not defined
videotitle=$(echo "${url}" | awk '$1 !~ /^https?:\/\// { print $0 }')
videotitle_fallback='video'
videotitle_default="${videotitle:=${videotitle_fallback}}-[${start}-${endtime}].mp4"


#===============================================================================
# one stream containing audio and video
#===============================================================================

# trim video and re-encode
one_stream_trim () {
video_url=$(echo "${urllist}" | awk 'BEGIN{ RS ="" ; FS ="\n" }{print $1}')
ffmpeg \
-hide_banner \
-stats -v panic \
-ss "${start}" \
-i "${video_url}" \
-t "${end}" \
-c:a aac \
-c:v libx264 -profile:v high \
-pix_fmt yuv420p -movflags +faststart \
-f mp4 \
"${outfile:=${videotitle_default}}"
}


#===============================================================================
# two streams containing audio and video
#===============================================================================

# trim video and re-encode
two_streams_trim () {
video_url=$(echo "${urllist}" | awk 'BEGIN{ RS ="" ; FS ="\n" }{print $1}')
audio_url=$(echo "${urllist}" | awk 'BEGIN{ RS ="" ; FS ="\n" }{print $2}')

# ffmpeg join audio and video and stream
ffmpeg \
-hide_banner \
-stats -v panic \
-ss "${start}" \
-i "${video_url}" \
-i "${audio_url}" \
-t "${end}" \
-map 0:0 -map 1:0 \
-c:a aac \
-c:v libx264 -profile:v high \
-pix_fmt yuv420p -movflags +faststart \
-f mp4 \
"${outfile:=${videotitle_default}}"
}


#===============================================================================
# case statement check for number of streams
#===============================================================================

case "${streamcount}" in
    1) one_stream_trim;; # single stream
    2) two_streams_trim;; # audio and video stream
    *) usage;;
esac