#!/bin/bash
usage(){
  cat << EOF

 $(basename $0) -d <directory> -s <rate> -p <prefix> -v <video_dir> -s <size>

 ——————————————————————————————————————————————————————————————————————————————————
 Opt | Variable      | Type  | Definition                           | Default value
 ——————————————————————————————————————————————————————————————————————————————————
 -d    directory       path    Directory path of images to convert    ./pics
 -r    rate            int     Convert only 1/N images                1
 -p    prefix          str     Images filename prefix.                ''
 -v    video_dir       path    Directory path to store video file.    ./videos
 -s    size            str     Images geometry.                       '1024x768'
 ——————————————————————————————————————————————————————————————————————————————————

EOF
  exit
}
panic(){ echo $@; exit 2;}

directory="./pics"
prefix=""
rate="1"
size='1024x768'
video_dir="./videos"

while getopts "hd:s:p:v:" o; do
  case "${o}" in
    h)
      usage
    ;;
    r)
      rate=${OPTARG}
    ;;
    d)
      directory=${OPTARG}
    ;;
    p)
      prefix=${OPTARG}
    ;;
    v)
      video_dir=$( realpath ${OPTARG} 2>/dev/null )
    ;;
    \?)
      panic "Unknown option at position $OPTIND. Exiting."
    ;;
  esac
done

# Safe test ffmpeg
which ffmpeg &>/dev/null || panic "No ffmpeg found. Exiting."

# Safe test directory
directory="$( realpath ${directory} 2>/dev/null )/"
[ -n "${directory}" ] && [ -d "${directory}" ] || panic "'${directory}' is not a valid directory. Exiting."

# Safe test prefix
[ -n "$( ls ${directory}/${prefix}* 2>/dev/null)" ] || panic "${directory}/${prefix}\* doesn't match any file. Exiting."

# Safe test rate
[ ${rate} -gt 0 ] || panic "Invalid rate '${rate}'"
pts=$( echo 1/$rate | bc -l )

# Safe test video_dir
video_dir="$( realpath ${video_dir} 2>/dev/null )/"
[ -n "${video_dir}" ] || panic "The video_dir option cannot be empty. Exiting."
[ -d "${video_dir}" ] || {
  read -p "'${video_dir}' does not exist, do you want to create it? [Y/n] : "
  REPLY=${REPLY:-Y}
  [ "N" == ${REPLY^^} ] && panic "The video directory must exist. Exiting."
  mkdir -p ${video_dir} 2>/dev/null || panic "Failed to create '${video_dir}'. Exiting"
}
[ -n "$( ls ${directory}/${prefix}* 2>/dev/null)" ] || panic "${directory}/${prefix}\* doesn't match any file. Exiting."

# Set video file name
date=$(date +%s)
video_file="${video_dir}$date.mp4"
echo -e "\nSaving to video file $video_file.\n"

ffmpeg -hide_banner -loglevel quiet -stats -pattern_type glob -i "pics/*.jpg" -filter:v "setpts=(${pts})*PTS"  -pix_fmt yuv420p -s "${size}"  -vcodec libx264  "${video_file}"