#!/bin/sh

## TODO: audio quality. Copy if AAC or OGG <320k.
## TODO: crop is not correct.
## TODO: handle srt encoding.

if [ -z "$(command -v ffmpeg)" ]; then
    echo "ffmpeg required."
    exit
fi

_printhelp()
{
    cat <<EOF
Usage: ${1##*/} [OPTIONS] FILES|FOLDERS

Transcode FILES or files found in FOLDERS to .mkv with x264 and ogg. Black
stripes are *not* cropped by default. Output files are the same as the original,
with time appended.

  -c:      Copy streams (no reencoding).
  -C:      Enable auto-crop.
  -f:      Remove source when done.
  -h:      Display this help.
  -o OPT:  Additional options.
  -s:      Sample of 5 minutes.
  -S MIN:  Sample of MIN minutes.
  -t:      Remove all "title" metadata.

Examples:

* Exchange stream 1 an 2 by first removing them, then reading them in the
  desired order.

  ${1##*/} -o '-map -0:1 -map -0:2 -map 0:2 -map 0:1' input.mkv

* Change audio stream 1 title and remove audio stream 2 title:

  ${1##*/} -o '-metadata:s:a:0 title="FR: OGG Stereo" -metadata:s:a:1 title=' input.mkv

EOF
}

SAMPLE=""
# USER_OPT="" ## Can use environment value.
VIDEO_FILTER=""
VIDEO_CODEC="-c:v libx264 -preset slow -crf 20"

## WARNING: we mix down audio to 2 channels with '-ac 2'. This greatly reduce
## file size and avoid any confusion for playback, which is often the case when
## converting DTS to any other format because DTS has embedded channel
## description which is not available in other formats.
AUDIO_CODEC="-c:a libvorbis -b:a 192k -ac 2"

## What to do if file exists:
# -y overwrite
# -n do not overwrite.
OVERWRITE="-n"
OPT_OVERWRITE=false

OPT_REMOVE_TITLE=false
OPT_CROP=false

while getopts ":cCfho:sS:t" opt; do
    case $opt in
        c)
            VIDEO_CODEC="-c:v copy"
            AUDIO_CODEC="-c:a copy" ;;
        C)
            OPT_CROP=true;;
        f)
            OVERWRITE="-y"
            OPT_OVERWRITE=true;;
        h)
            _printhelp "$0"
            exit 1 ;;
        o)
            USER_OPT="$OPTARG" ;;
        s)
            SAMPLE="-ss 60 -t 360" ;;
        S)
            SAMPLE="-ss 60 -t $((60*$OPTARG))" ;;
        t)
            OPT_REMOVE_TITLE=true ;;
        ?)
            _printhelp "$0"
            exit 1 ;;
        :)
            echo "Missing argument."
            _printhelp "$0"
            exit 1 ;;
    esac
done

shift $(($OPTIND - 1))


if [ $# -eq 0 ]; then
    _printhelp "$0"
    exit
fi

## Zsh compatibility. We need it otherwise word splitting of parameter like
## SAMPLE will not work.
STATUS="$(set -o | grep 'shwordsplit' | awk '{print $2}')"
[ "$STATUS" = "off" ] && set -o shwordsplit

_duration()
{
    ## In seconds.
    ffmpeg -i "$1" 2>&1 | awk '/Duration/ {split($2, time, /:|\./); print time[1]*60*60 + time[2]*60 + time[3]}'
}

_highfreq()
{
    awk 'BEGIN{max=0} /crop=/ {t[$NF]++; if (t[$NF]>max) {max=t[$NF]; val=$NF}} END{print val}'
}

_cropvalue()
{
    ## For 5 different timeslices of 1 second at every 1/6th of the video, we
    ## sample the crop values. We keep the values with highest frequency.
    STEP=$(($(_duration "$1")/6))
    for i in $(seq $STEP $STEP $((5*$STEP))); do
        echo -ss $i -t 10
        ffmpeg -ss $i -t 10 -i "$1" -vf "cropdetect=24:16:0" -f null - 2>&1
    done | _highfreq
}

_tc_transcode()
{
    cat<<EOF
================================================================================
File:          $1

User options:  ${USER_OPT:-None}
Sample:        ${SAMPLE:-No}
Clear 'Title': $OPT_REMOVE_TITLE
Crop:          $OPT_CROP
================================================================================
EOF

    STREAM_TITLE=""
    if $OPT_REMOVE_TITLE; then
        STREAM_NUM=$(ffmpeg -i "$1" 2>&1 | grep -c 'Stream')
        for i in $(seq 0 $STREAM_NUM); do
            STREAM_TITLE="${STREAM_TITLE}-metadata:s:$i title= "
        done
    fi

    if $OPT_CROP; then
        VIDEO_FILTER="-vf $(_cropvalue "$1")"
    fi

    OUTPUT="${1%.*}-$(date '+%F-%H%M%S').mkv"
    ffmpeg $OVERWRITE -i "$1" \
        $VIDEO_CODEC $VIDEO_FILTER \
        $AUDIO_CODEC \
        -c:s copy \
        -map 0 $STREAM_TITLE \
        $SAMPLE $USER_OPT "$OUTPUT"

    if $OPT_OVERWRITE; then
        rm -f "$1"
        mv -f "$OUTPUT" "${1%.*}.mkv"
    fi
    echo
}

for i in "$@"; do

    ## Argument is a folder. We search for all video files in there.
    if [ -d "$i" ]; then

        ## WARNING: ffmpeg should not be called from within a while<<EOF loop
        ## since it continues to read input while running. However IFS needs to
        ## be restored for wordsplitting to work correctly.
        OLDIFS="$IFS"
        IFS="
"

        for j in $(find "$i"  \( \
            -iname '*.mkv' -o \
            -iname '*.mp4' -o \
            -iname '*.avi' -o \
            -iname '*.webm' -o \
            -iname '*.flv' -o \
            -iname '*.wmv' -o \
            -iname '*.mpg' \) ); do
            IFS="$OLDIFS"
            _tc_transcode "$j"
            IFS="
"
        done
        IFS=$OLDIFS

    else
        ## Argument is a regular file.
        _tc_transcode "$i"
    fi

done

## Restore Zsh previous options. This will not turn off shwordsplit if it
## was on before calling the function.
[ "$STATUS" = "off" ] && set +o shwordsplit