#! /bin/zsh
# This is a pretty processor intensive set of tasks! You should probably nice this script
# as in call it with nice -n 10 "every_frame_a_wallpaper.zsh /path/to/video.mkv"

SCRIPT_NAME=$(basename "$0")

# I like a nice log file for my cron jobs
function LOG() {
  echo -e "$(date --iso-8601=seconds): [$SCRIPT_NAME] :  $1"
}

# set up some options
local begin_skip_minutes=5
local end_skip_minutes=10
local wallpaper="$HOME/Pictures/wallpaper.png"
local usage=(
	"$SCRIPT_NAME [-h|--help]"
	"$SCRIPT_NAME [-b|--begin_skip_minutes] [-e|--end_skip_minutes] [<video file path>]"
	"Extract a single random frame from a movie and set it as wallpaper"
	"By default, skips 5 minutes from the beginning and 10 from the end, but this is overridable"

)

# the docs suck on zparseopts so let this be a reference for next time
# -D pulls parsed flags out of $@
# -F fails if we find a flag that wasn't defined
# -K allows us to set default values without zparseopts overwriting them
# Remember that the first dash is automatically handled, so long options are -opt, not --opt
zparseopts -D -F -K -- \
	{h,-help}=flag_help \
	{b,-begin_skip_minutes}:=begin_skip_minutes \
	{e,-end_skip_minutes}:=end_skip_minutes \
	|| return 1

[[ -z "$flag_help" ]] || {print -l $usage && return }
if [[ -z "$@" ]] {
   print -l "A video file path is required"
   print -l $usage && return

} else {
   MOVIE="$@"
}

if [[ $DISPLAY ]]
then
  LOG "interactively running, not in cron"
else
  LOG "Not running interactively, time to export the session's environment for cron"
  export $(xargs -0 -a "/proc/$(pgrep gnome-session -n -U $UID)/environ") 2>/dev/null
fi

LOG "skipping $begin_skip_minutes[-1] minutes from the beginning"
LOG "skipping $end_skip_minutes[-1] minutes from the end"
LOG "outputting the wallpaper to $wallpaper"
LOG "using file $MOVIE"

LOG "Let's get a frame from ${MOVIE}";


LOG "What's the duration of the movie?"
DURATION=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 \
  $MOVIE);
DURATION=$(printf '%.0f' $DURATION);

LOG "Duration looks like ${DURATION} seconds";

LOG "what's the frame rate?"

FRAMERATE=$(ffprobe -v error -select_streams v:0 \
  -show_entries \
  stream=r_frame_rate \
  -print_format default=nokey=1:noprint_wrappers=1 $MOVIE)




FRAMERATE=$(bc -l <<< "$FRAMERATE");

FRAMERATE=$(printf "%.0f" $FRAMERATE);

LOG "Looks like it's roughly $FRAMERATE"

FRAMECOUNT=$(bc -l <<< "${FRAMERATE} * ${DURATION}");
FRAMECOUNT=$(printf '%.0f' $FRAMECOUNT)
LOG "So the frame count should be ${FRAMECOUNT}";


SKIP_MINUTES=$begin_skip_minutes[-1]
SKIP_CREDITS_MINUTES=$end_skip_minutes[-1]

LOG "We want to skip $SKIP_MINUTES from the beginning and $SKIP_CREDITS_MINUTES from the end".

SKIP_BEGINNING_FRAMES=$(bc -l <<< "${FRAMERATE} * $SKIP_MINUTES * 60");
LOG "So $SKIP_MINUTES * 60 seconds * $FRAMERATE frames per second = $SKIP_BEGINNING_FRAMES frames to skip from the beginning."
SKIP_ENDING_FRAMES=$(bc -l <<< "${FRAMERATE} * $SKIP_CREDITS_MINUTES * 60");
LOG "So $SKIP_CREDITS_MINUTES * 60 seconds * $FRAMERATE frames per second = $SKIP_ENDING_FRAMES frames to skip from the ending."

USEABLE_FRAMES=$(bc -l <<< "$FRAMECOUNT - $SKIP_BEGINNING_FRAMES - $SKIP_ENDING_FRAMES");
UPPER_FRAME=$(bc -l <<<"$FRAMECOUNT - $SKIP_ENDING_FRAMES")
LOG "That leaves us with ${USEABLE_FRAMES} usable frames between $SKIP_BEGINNING_FRAMES and $UPPER_FRAME";

FRAME_NUMBER=$(shuf -i $SKIP_BEGINNING_FRAMES-$UPPER_FRAME -n 1)
LOG "Extract the random frame ${FRAME_NUMBER} to ${wallpaper}";
LOG "This takes a few minutes for large files.";
ffmpeg \
  -loglevel error \
  -hide_banner \
  -i $MOVIE \
  -vf "select=eq(n\,${FRAME_NUMBER})" \
  -vframes 1 \
  -y \
  $wallpaper


WALLPAPER_PATH="file://$(readlink -f $wallpaper)"
LOG "Set the out file as light and dark wallpaper - using ${WALLPAPER_PATH}";
gsettings set org.gnome.desktop.background picture-uri-dark "${WALLPAPER_PATH}";
gsettings set org.gnome.desktop.background picture-uri "${WALLPAPER_PATH}";

# generate a neat new background every morning
0 4 * * * nice -n 10 ~/crons/every_frame_a_wallpaper.zsh -b 5 -e 12 /home/mk/Videos/Movies/Spider-Man_Across_the_Spider-Verse.mkv >> ~/.logs/every_frame_a_wallpaper/`date +"\%F"`-run.log 2>&1