#!/bin/bash

#credit/source:
#https://wiki.archlinux.org/index.php/Convert_Any_To_Mp3
#deps: MPlayer, mutagen and lame

DEFAULT_OUTPUT_DIR=/tmp/mp3ify
QUALITY=2
VBR_QUALITY=4
MIN_BITRATE=64
MAX_BITRATE=256
SAMPLE_FREQ=44.1


function any_to_mp3 {

  PIPE=`mktemp -u -t mp3ify.pipe.XXXXXX`
  mkfifo "$PIPE"

  mplayer -ao pcm -ao pcm:file="$PIPE" "$INPUT_FILE" -noconsolecontrols > /dev/null 2>&1 &

  lame -m j -q $QUALITY -v -V $VBR_QUALITY -b $MIN_BITRATE \
       -B $MAX_BITRATE -s $SAMPLE_FREQ "$PIPE" "$OUTPUT_FILE" > /dev/null 2>&1

  rm "$PIPE"

  python2 -c "
import mutagen
input = mutagen.File(\"$INPUT_FILE\", easy = True)
output = mutagen.File(\"$OUTPUT_FILE\", easy = True)
for tag in [ 'artist', 'album', 'tracknumber', 'date', 'genre', 'title' ]:
  value = input.get(tag)
  if value: output[tag] = value[0]
output.save(v1=2)"
}


function usage {

  echo "mp3ify <input_dir> [<output_dir>]

  Transforms structure <input_dir>/X/Y/.../Z into structure <output_dir>/X/Y/.../Z
  according to the following rules:

    flac, ogg, m4a, ape, aac, mpc files will be encoded to mp3 preserving tags.

    Everything else will be copied without modification.

  Requires: mplayer, lame, mutagen.
"
  exit 1
}


INPUT_DIR="$1"
[ -d "$INPUT_DIR" ] || usage
OUTPUT_DIR="${2:-$DEFAULT_OUTPUT_DIR}"

find "$INPUT_DIR" -name '*.*' | while read INPUT_FILE
do
  INPUT_EXTENSION="${INPUT_FILE##*.}"
  OUTPUT_FILE="$OUTPUT_DIR/${INPUT_FILE#$INPUT_DIR}"
  mkdir -p "`dirname "$OUTPUT_FILE"`"

  case $INPUT_EXTENSION in
  flac|m4a|ogg|ape|aac|mpc)
    OUTPUT_FILE="${OUTPUT_FILE%.$INPUT_EXTENSION}.mp3"
    echo -n "Converting ${INPUT_FILE##*/}... "
    any_to_mp3
    ;;
  *)
    echo -n "Copying ${INPUT_FILE##*/}... "
    cp "$INPUT_FILE" "$OUTPUT_FILE"
    ;;
  esac

  echo "done."
done