Fix mp3 meta tags based on filename & path

.gitignore

*.mp3

.rvmrc

rvm ree

Gemfile

# A sample Gemfile
source "http://rubygems.org"

# gem "rails"
gem 'ruby-mp3info'

Gemfile.lock

GEM
  remote: http://rubygems.org/
  specs:
    ruby-mp3info (0.6.16)

PLATFORMS
  ruby

DEPENDENCIES
  ruby-mp3info

update-mp3-meta-tags.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'mp3info'
require 'fileutils'

def parse_dirname(str)
  album = File.basename str
  artist = File.dirname str
  if artist == '.'
    artist = album
    album = nil
  end
  [artist, album]
end

def parse_filename(str)
  str = str[0..-5]
  parts = str.split('-')

  raise str if parts.size > 3
  
  artist = nil
  album = nil
  title = nil

  if parts.size == 1
    title = parts.first
  elsif parts.size == 2
    artist = parts.first
    title = parts.last
  elsif parts.size == 3
    (artist, album, title) = parts
  end

  title = filter_title(title)
  
  [artist, album, title]
end

def filter_title(s)
  s = s.gsub(/^[0-9]+[ \.]*/, '')
end

Dir["**/*.[mM][pP]3"].each do |f|

  filename = File.basename f
  dirname = File.dirname f
  has_dir = dirname != '.'

  puts "=" * 20
  puts "  file: #{f}"

  artist = ''
  album = ''
  title = ''

  if has_dir
    (artist, album) = parse_dirname(dirname)
    title = filename[0..-5]
    title = filter_title(title)

    if title =~ /-/ && !album
      parts = title.split('-')
      album = parts.first
      title = parts[1..-1].join('-')
    end
  else
    (artist, album, title) = parse_filename(filename)
  end

  artist.strip! if artist
  album.strip! if album
  title.strip! if title

  puts "artist: '#{artist}'" if artist
  puts "album : '#{album}'" if album
  puts "title : '#{title}'"

  puts ""

  Mp3Info.open(f, :encoding => 'utf-8') do |mp3|
    mp3.tag.artist = artist
    mp3.tag.album = album
    mp3.tag.title = title
  end
end