#!/usr/bin/ruby -w
# -*- ruby -*-

require 'pathname'
require 'optparse'

$verbose = false

def quote(str)
  str.gsub(%r{([\'\"])}) { "\\" + $1 }
end

def log(msg)
  puts msg if $verbose
end

class FlacFile
  attr_reader :mp3name

  MP3_FIELDS = { 
    # flac           # mp3/id3
    'ALBUM'       => 'A',
    'ARTIST'      => 'a',
    'DATE'        => 'y',
    'GENRE'       => 'g',
    'TITLE'       => 's',
    'TRACKNUMBER' => 't',
    'TRACKTOTAL'  => 'T',
  }
  
  def initialize(flacname)
    @flacname = flacname
    @mp3name  = flacname.sub(%r{.flac$}, '.mp3')
  end

  def mp3_exist?
    Pathname.new(@mp3name).exist?
  end

  def encode
    log "encoding flac to mp3 ..."
    cmd = "flac -sdc \"#{@flacname}\" | lame -h - \"" + quote(@mp3name) + "\""

    log "cmd: #{cmd}"

    IO.popen(cmd).readlines
  end

  def tag
    mfcmd = "metaflac --export-tags-to=- \"" + quote(@flacname) + "\""
    
    log "mfcmd: #{mfcmd}"

    fields = Hash.new
    
    IO.popen(mfcmd).readlines.each do |line|
      line.chomp!
      name, value = line.split('=')
      fields[name] = value
      log line
    end
    
    id3tagcmd = "id3tag "  

    id3tags = MP3_FIELDS.sort.collect do |flactag, id3tag|
      next unless val = fields[flactag]
      
      case flactag 
      when 'GENRE'
        val ||= 9                # 9=metal; 22=death
      when 'DATE'
        val = val[0 .. 3]
      end
      
      log "val: #{val}"
      
      "-#{id3tag}\"" + quote(val) + "\""
    end.compact
    
    id3tagcmd << id3tags.join(" ") << "\"" + quote(@mp3name) + "\""
    
    log "id3tagcmd: #{id3tagcmd}"
    
    IO.popen(id3tagcmd).readlines
  end
end

$retag = false

def process(fname)
  flacfile = FlacFile.new(fname)
  
  mp3exists = flacfile.mp3_exist?
  
  unless mp3exists
    flacfile.encode
  end
  
  if !mp3exists || $retag
    flacfile.tag
  end
end

opts = OptionParser.new do |opts|
  prog = File.basename(__FILE__)
  opts.banner = "Usage: #{prog} [options] FLACFILE ..."

  opts.on("--retag",
          "Tag the MP3 files, without the dependency check") { |$retag| }

  opts.on("--verbose", "-v",
          "Verbose output") { |$verbose| }
end

begin
  opts.parse!(ARGV)
rescue OptionParser::ParseError => e
  puts e
  puts opts.banner
  exit(-2)
end

args = ARGV

args.sort.each do |arg|
  pn = Pathname.new(arg)
  if pn.directory?
    pn.find do |x| 
      if x.file? && x.extname == ".flac"
        process(x.to_s)
      end
    end
  else
    process(arg)
  end
end