#!/bin/sh

# Written by Juliusz Chroboczek.  Do whatever you want with this script.

# Recode wav/flac/alac/whatever into flac/mp3/aac/ogg preserving tags.

# If the input and output formats are identical, builds a new container
# without actually recoding anything (unless -e has been used).  This is
# useful for converting mp4 videos to audio-only, or for reordering the
# chunks in "unstreamable" m4a files.

# I usually do something like:
#   find . -maxdepth 1 -name '*.wav' -print0 | xargs -0 -n 1 -P 2 recode-audio

# Known bugs:
#  - there's basically no error handling;
#  - uses Nero's proprietary AAC encoder, since neither FAAC nor ffmpeg do
#    a good job encoding AAC.

format=mp3                      # Default output format when there's no
                                # second argument

while getopts "f:q:let" name; do
    case $name in
        f) format="$OPTARG";;   # Effective when there's no second argument
        q) quality="$OPTARG";;  # Output-format specific, see defaults below
        l) lc=true;;            # Disable AAC-HE, for iPods
        e) force_encode=true;;  # Disable lossless remuxing for mp4->m4a
        t) tags_only=true;;     # Only copy tags, don't recode
        *) exit 1;;
    esac
done

shift $(($OPTIND - 1))

if [ $# -gt 2 ] ; then
    echo "Too many arguments" >&2 
    exit 1
fi

lame_opts="--vbr-new -h -V ${quality:-3}"
nero_opts="-q ${quality:-0.5} ${lc:+-lc}"
ogg_opts="-q ${quality:-5}"
flac_opts=""

if="$1"
of="${2:-${1%.*}."$format"}"

format="${of##*.}"

if [ "$if" = "$of" ]; then
    echo "Converting to self?" >&2
    exit 1
fi

locale | grep -q 'LC_CTYPE.*UTF-8'
[ $? -eq 0 ] || echo "Warning: running in weird locale." >&2

tags="title album artist track tracknumber totaltracks disc discnumber totaldiscs genre comment year date copyright isrc label composer author tempo"
# Only in mp4: track, disc, year, tempo
# Only in Ogg: tracknumber, discnumber, date, performer, composer, author

for tag in $tags; do
    eval unset $tag
done

# Ogg and Flac are not case-sensitive.  Sigh.
tolower() {
    while read line; do
        echo -n "${line%%=*}" | tr [A-Z] [a-z]
        echo "=${line#*=}"
    done
}

flac_tags () {
    for tag in $tags; do
        metaflac --no-filename --show-tag="$tag" "$1"
    done
}

parse_tags() {
    case "$1" in
        *.mp3|*.mp2|*.mpg)
            title="$(mp3info -p %t "$1")"
            album="$(mp3info -p %l "$1")"
            artist="$(mp3info -p %a "$1")"
            track="$(mp3info -p %n "$1")"
            genre="$(mp3info -p %g "$1")"
            comment="$(mp3info -p %c "$1")"
            year="$(mp3info -p %y "$1")"
            copyright="$(mp3info -p %C "$1")"
            ;;
        *.ogg)
            eval "$(vorbiscomment -l "$1" | tolower | \
                    sed -e "s/'/'\\\\''/" -e "s/=/='/" -e "s/$/'/")"
            ;;
        *.flac)
            eval "$(flac_tags "$1" | tolower | \
                    sed -e "s/'/'\\\\''/" -e "s/=/='/" -e "s/$/'/")"
            ;;
        *.mp4|*.m4a)
            eval "$(neroAacTag -list-meta "$1" 2>&1 | \
                    sed -n -e '1,/Metadata list:/!p' | \
                    sed -n -e '/End of metadata/,$!p' | \
                    sed -n -e '/=/p' | \
                    sed -e 's/^[ 	]*//' \
                        -e "s/'/'\\\\''/" \
                        -e "s/ = /='/" -e "s/$/'/")"
            ;;
        # APE?
        *)
            echo "Warning: cannot get tags of $1" >&2
            ;;
    esac

    # Convert mp4 to Ogg syntax
    [ -z "$tracknumber" ] && tracknumber="$track"
    [ -z "$discnumber" ] && discnumber="$disc"
    [ -z "$date" ] && date="$year"

    # Convert Ogg to mp4 syntax
    [ -z "$track" ] && track="$tracknumber"
    [ -z "$disc" ] && disc="$discnumber"
    [ -z "$year" ] && year="$(echo $date | cut -b 1-4)"
}

decoder() {
    case "$1" in
        *.flac)
            if [ -z "$2" ] ; then
                flac -s -dc -- "$1"
            else
                flac -s -d -o "$2" -- "$1"
            fi ;;
        *.ogg) oggdec -Q -o "${2:--}" -- "$1" ;;
        *.mp4|*.m4a) neroAacDec -if "$1" -of "${2:-/dev/stdout}" ;;
        *) ffmpeg -i "$1" -vn -f wav -y "${2:--}" ;;
    esac
}

# Second argument specifies whether we use Ogg tags
all_tags() {
    for tag in $tags; do
        eval value=\$$tag
        quotedval="$(echo "$value" | sed "s/'/'\\\\''/g")"
        if $2 ; then
            case "$tag" in
                track|disc|year|tempo)
                    value='' ;;
            esac
        else
            case "$tag" in
                tracknumber|discnumber|date|performer|composer|author)
                    value='' ;;
            esac
        fi
        [ -z "$value" ] || echo $1\'$tag=$quotedval\'
    done
}

set_tags() {
    quoted="'$(echo "$1" | sed "s/'/'\\\\''/g")'"
    case "$1" in
        *.mp4|*.m4a)
            eval neroAacTag $(all_tags -meta: false) "$quoted"
            ;;
        *.ogg)
            eval vorbiscomment $(all_tags "-t " true) "$quoted"
            ;;
        *.flac)
            eval metaflac $(all_tags "--set-tag=" true) "$quoted"
            ;;
        *)
            echo "Warning: cannot set tags of $1" &>2
            ;;
    esac
}

encoder() {
    quoted="'$(echo "$1" | sed "s/'/'\\\\''/g")'"
    case "$1" in
        *.flac)
            eval flac $flac_opts -s $(all_tags '-T ' true) -o \'"$1"\' -
            ;;
        *.ogg)
            eval oggenc -Q $(all_tags '--comment ' true) $ogg_opts -o "$quoted" -
            ;;
        *.mp3)
            lame --quiet $lame_opts \
                 --tt "$title" \
                 --tn "$track${totaltracks:+/$totaltracks}" \
                 --tg "$genre" \
                 --ty "$year" \
                 --ta "$artist" \
                 --tl "$album" \
                 - "$1"
            ;;
        *.mp4|*.m4a)
            neroAacEnc -ignorelength $nero_opts -if - -of "$1"
            set_tags "$1"
            ;;
        *) echo "Unknown output file format" >&2; exit 1 ;;
    esac
}

parse_tags "$if"

if [ ! -z "$tags_only" ]; then
    set_tags "$of"
    exit
fi

if [ -z "$force_encode" ]; then
    case "$if-$of" in
        *.mp4-*.mp4|*.mp4-*.m4a|*.m4a-*.mp4|*.m4a-*.m4a|*.flv-*.mp4|*.flv-*.m4a)
            f="$(mktemp /tmp/XXXXXX.mp4)"
            ffmpeg -i "$if" -vn -acodec copy -y "$f" -map_meta_data 0:0
            qt-faststart "$f" "$of"
            rm "$f"
            exit
            ;;
        *.mp3-*.mp3|*.mpg-*.mp3|*.ogg-*.ogg|*.flac-*.flac)
            exec ffmpeg -i "$if" -vn -acodec copy "$of" -map_meta_data 0:0
            ;;
    esac
fi

case "$if-$of" in
    *.wav-*.ogg|*.flac-*.ogg)
        exec oggenc -Q $ogg_opts -o "$of" "$if"
        ;;
    *.wav-*.flac|*.flac-*.flac)
        exec flac $flac_opts -s -o "$of" "$if"
        ;;
    *.*-*.wav)
        decoder "$if" "$of"
        ;;
    *.wav-*.*)
        encoder "$of" < "$if"
        ;;
    *)
        decoder "$if" | encoder "$of"
        ;;
esac