#!/usr/bin/ruby

require 'getoptlong'
require 'id3lib'
require 'flacinfo'
require 'tempfile'

def create_mp3(sourcefile, destfile)
  fork do
    rd, wr = IO.pipe

    if fork then
      STDOUT.reopen(wr)
      rd.close
      wr.close
      exec('sox', '--replay-gain=track', sourcefile, '-t', 'wav', '-')
    else
      STDIN.reopen(rd)
      STDOUT.reopen('/dev/null', 'w')
      rd.close
      wr.close
      exec('lame', '--r3mix', '-p', '-B', '192', '-V', '8', '-', destfile)
    end
  end
  Process.waitall
  puts 'Encoding finished.'
end

def get_flac_metadata(flacfile)
  return FlacInfo.new(flacfile).tags
end

def flac_key_to_id3v2(key)
  return case key
           # Standard fields.
         when "TITLE"        then :TIT2
         when "VERSION"      then :TIT3
         when "ALBUM"        then :TALB
         when "TRACKNUMBER"  then :TRCK
         when "ARTIST"       then :TPE2
         when "PERFORMER"    then :TPE1
         when "COPYRIGHT"    then :TCOP
         when "LICENSE"      then :TOWN
         when "ORGANIZATION" then :TPUB
         # DESCRIPTION
         when "GENRE"        then :TCON
         #when "DATE"         then :TDRC
         # LOCATION
         # CONTACT
         when "ISRC"         then :TSRC

           # My additions
         when "SUBTITLE"        then :TIT3
         when "ORIGINAL_ALBUM"  then :TOAL
         when "ORIGINAL_ARTIST" then :TOPE
         when "COMPOSER"        then :TCOM
         when "CONDUCTOR"       then :TPE3
         when /^DIS[CK]NUMBER$/ then :TPOS
         when "YEAR"            then :TYER
         when "URL"             then :WXXX

           # Seen elsewhere
         when "BPM"     then :TBPM
         when "ENCODER" then :TSSE
         end
end

def get_track_line(trackno, metadata)
  if metadata["TOTALTRACKS"] then
    return trackno + "/" + metadata["TOTALTRACKS"]
  elsif metadata["TRACKTOTAL"] then
    return trackno + "/" + metadata["TRACKTOTAL"]
  else
    return trackno
  end
end

def set_mp3_metadata(mp3file, metadata)
  tag = ID3Lib::Tag.new(mp3file, ID3Lib::V_BOTH)

  metadata.each { |key, value|
    id3v2_key = flac_key_to_id3v2(key)
    if id3v2_key == :TRCK then
      tag.set_frame_text(id3v2_key, get_track_line(value, metadata))
    elsif id3v2_key then
      tag.set_frame_text(id3v2_key, value)
    end
  }

  tag.update!
end

def copy_pictures(flacfile, mp3file)
  flacinfo = FlacInfo.new(flacfile)
  mp3info = ID3Lib::Tag.new(mp3file)

  for i in 1..flacinfo.picture["n"]
    # FlacInfo only supports writing the picture to a file, so we cheat a
    # little to get it into memory.
    picture_in = File.new(flacfile, "rb")
    picture_in.seek(flacinfo.picture[i]['raw_data_offset'], IO::SEEK_CUR)
    mp3info << {
      :id          => :APIC,
      :mimetype    => flacinfo.picture[i]["mime_type"],
      :picturetype => flacinfo.picture[i]["type_int"],
      :description => flacinfo.picture[i]["description_string"],
      :textenc     => 0,
      :data        => picture_in.read(flacinfo.picture[i]['raw_data_length'])
    }
    picture_in.close
  end

  mp3info.update!
end

dest_dir = ''

opts = GetoptLong.new(
    [ "--destination", "-d", GetoptLong::REQUIRED_ARGUMENT ]
)

opts.each do |opt, arg|
  case opt
  when "--destination"
    dest_dir = arg + '/'
  end
end

ARGV.each { |sourcefile|
  base = File.basename(sourcefile, '.flac')
  destfile = dest_dir + base + '.mp3'

  create_mp3(sourcefile, destfile)
  set_mp3_metadata(destfile, get_flac_metadata(sourcefile))
  copy_pictures(sourcefile, destfile)
}