#!/bin/bash
# 20190822 | tatze

# ------------------------------------------
global_path=~/Videos/_reduced/
local_path='reduced/'
# ------------------------------------------

# create directory if it's non-existent
function dir {
  if [ ! -d "$1" ]
    then
    printf "${bold}creating folder $1 ${normal}\n"
    mkdir -p -- "$1"
    if [ ! -d "$1" ]
      then
      printf "${bold}creating folder $1 FAILED, aborting script.${normal}\n"
      exit 1
    fi
  fi
}

# terminal output: bold or normal?
bold=$(tput bold)
normal=$(tput sgr0)

# your choice ...
printf "\n${bold}Where shall the reduced images be created? ${normal}
1. locally ($local_path) ${bold}[default]${normal}
2. globaly ($global_path)\n${bold}
[?] : ${normal}"
read RP

case $RP in
  2)
    printf "using $global_path ${normal}\n\n"
    path=$global_path
    pth=$(basename $PWD)/
    path+=$pth
    ;;
  *)
    printf "using $local_path ${normal}\n\n"
    path=$local_path
    ;;
esac

dir "$path"

find . -iregex '.*\.mp4$' -not -iregex '.*_reduced\.mp4$' -not -path "$path/*" -print0 | sort -z |
while IFS= read -rd '' file; do
  # path for reduced files
  rd=$path${file%/*}
  dir "$rd"
  # get basename
  bn=${file##*/}
  # create filename for reduced version
  bn="${bn%.*}_reduced.${bn##*.}"
  # create filename for temp version
  tmp="${bn%.*}_temp.mp4"
  # check if reduced file already exists
  if [ ! -f "$rd/$bn" ]
  # nope, go on
  then
    printf "compressing video $file ... "
    # prepending < /dev/null to prevent characters bleeding to ffmpeg
    # using temporary file to avoid faulty files when escaping the loop (next run the script will re-do $file then)
    < /dev/null ffmpeg -y -i "$file" \
                       -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k \
                       -movflags +faststart -vf scale=-2:720,format=yuv420p \
                       -v 0 \
                       "$rd/$tmp"
    printf "done.\ncopying metadata ..."
    # copy metadata to the reduced version
    < /dev/null ffmpeg -i "$file" \
                       -i "$rd/$tmp" -map 1 -map_metadata 0 \
                       -v 0 \
                       -c copy "$rd/temp_for_metadata".mp4
    # move the reduced file to its final version
    mv "$rd/temp_for_metadata.mp4" "$rd/$bn"
    # remove the temporary file
    rm "$rd/$tmp"
    # preserve modified timestamp
    touch -r "$file" "$rd/$bn"
    printf "done.\nhere it is: $rd/$bn\n\n"
  # file exists, skip it
  else
    printf "$rd/$bn already exists, skipping.\n"
  fi
done