#!/usr/bin/env bash
# Copyright: Julien Moutinho <julm+camera@sourcephile.fr>
# License: AGPL-3.0-or-later
#

cd "${0%/*}"
set -eu
shopt -s nullglob

ffmpeg_ () { local -; set -x; nice -19 ffmpeg </dev/null -hide_banner -loglevel warning -stats -y "$@"; }
mv_ () { local -; mv -i >&2 "$@"; }
set -x
for dir in "$@"; do
  IFS=/ read -r user year x month x <<<"$dir"
  test -n "$year" || exec "$0" "$user"/2*/src/*/
  test -n "$month" || exec "$0" "$user"/"$year"/src/*/
  pushd "$user/$year" >/dev/null
  test -d src/"$month" || { popd; continue; }
  (cd src; find -L "$month" -type f -size +200M -printf '%f %p\n') | sort -t/ -k1.5 | cut -f2 -d ' ' |
  while read -r src; do
    echo >&2 "$dir: processing $year/src/$src"
    base=${src%.*}
    name=${base#*/}
    id=${name%%.*}
    mkdir -p {tmp,wip,old}/reencode/"${base%/*}"
    case "$src" in
      *.mp4)
        # Slow, but needed to make wide videos span two columns of the CSS grid
        orient=$(ffprobe -v 0 -select_streams v:0 -show_entries stream_side_data=rotation -of default=nw=1:nk=1 src/"$src")
        psize=720
        crf=40
        preset=7
        ext="preset=$preset.crf=$crf.${psize}p.av1.webm"
        if [ -z "$orient" ]; then scale="-2:${psize}"; else scale="${psize}:-2"; fi
        need_opus () {
          test tmp/reencode/"$base".opus -nt src/"$src" || {
            ffmpeg_ -i src/"$src" \
              -map 0:a -c:a libopus -b:a 64k -application voip \
              wip/reencode/"$base".opus
            mv_ {wip,tmp}/reencode/"$base".opus
          }
        }
        test src/"$base.$ext" -nt src/"$src" || {
          need_opus
          # See https://gitlab.com/AOMediaCodec/SVT-AV1/-/blob/master/Docs/CommonQuestions.md
          # See https://gist.github.com/BlueSwordM/86dfcb6ab38a93a524472a0cbe4c4100
          # See https://www.streamingmediaglobal.com/Articles/ReadArticle.aspx?ArticleID=154488
          # -preset       Range from 0 to 13, with higher numbers providing a higher encoding speed;
          # -crf          Range is 0-63, with the default being 50.
          #               Lower values correspond to higher quality and greater file size
          # yuv420p
          # yuv420p10le   can represent more shades of grey and colors
          #               and is less prone to certain artifacts, such as color
          #               banding and loss of detail in low luma areas,
          #               cost in terms of resulting file size (~5%),
          #               can also be more compute-intensive than 8-bit in some decoders
          # tune=0        subjective mode often results in an image with greater
          #               sharpness and is intended to produce a result that appears to humans
          #               to be of high quality (as opposed to doing well on basic objective measures,
          #               such as PSNR)
          # scd=1         biases the encoders' scene detection to insert more intra refreshes if needed,
          #               and reduce temporal dependencies around scene-changes.
          # scm=0         screen content mode decision making. 0 is best for live-action.
          # fast-decode=3 trade compression efficiency for less CPU time when decoding
          #               for preset 5-7: levels 1-3 (3 being faster) are supported.
          # FIXME: set fast-decode to 3 available on newer svt-av1
          ffmpeg_ -i src/"$src" -i tmp/reencode/"$base".opus \
            -map 0:v \
              -filter:v format=yuv420p,scale="$scale" \
              -c:v libsvtav1 -preset "$preset" -crf "$crf" \
                -svtav1-params tune=0:enable-overlays=1:scd=1:scm=0:fast-decode=1 \
            -map 1:a -c:a copy \
            wip/reencode/"$base.$ext"
          mv_ {wip/reencode,src}/"$base.$ext"
          mv_ {src,old/reencode}/"$src"
        }
        ;;
    esac
  done
  rm -vrf {tmp,wip}/reencode
  popd >/dev/null
done