#!/usr/bin/env ruby
#
# omptagger
# http://github.com/omp/omptagger
# Modify and display metadata of audio files.
#
# Copyright 2007-2010 David Vazgenovich Shakaryan <dvshakaryan@gmail.com>
# Distributed under the terms of the GNU General Public License v3.
# See http://www.gnu.org/licenses/gpl.txt for the full license text.

require 'getoptlong'
require 'rubygems'
require 'TagLib'

class Metadata
  def output(tag, val)
    spacing = 2 + @tags.keys.inject(0) do |length, object|
      object.length > length ? object.length : length
    end - tag.length

    puts '    ' + tag + ' ' * spacing + val
  end
end

class VorbisComment < Metadata
  def view
    puts '  Viewing tags:'

    if @tags.empty?
      puts '    No tags are set.'
      return
    end

    @tags.sort.each do |tag, val|
      val.each do |val|
        output(tag, val)
      end
    end
  end
end

class FLAC < VorbisComment
  def initialize(file)
    @filename = File.expand_path(file)
    @write = false

    @file = TagLib::FLAC::File.new(file)
    @tags = @file.xiphComment.fieldListMap.hash
  end
end

def help
  puts <<-end
Usage: omptagger [options] [files]

Options:
  --view        -v  View all tags
  --view-tag    -t  View a tag
  --add-tag     -a  Add a tag
  --set-tag     -s  Set a tag
  --remove      -r  Remove all tags
  --remove-tag  -d  Remove a tag
  --generate    -g  Generate tags based on filename
  --rename      -m  Generate filename based on tags
  --scheme      -n  Specify a file naming scheme
  --list        -l  Display available scheme keys
  --help        -h  Display help information
  --pretend     -p  Do not finalise changes

Notes:
  * Actions are executed in the order they are specified.
  * The default file naming scheme is Artist - Title.
  end

  exit
end

def list
  puts <<-end
Keys   Vorbis Comments   ID3v2 Frames
----   ---------------   -------------
 %a    Artist            Artist
 %b    Album             Album
 %d    Date              Year
 %n    TrackNumber       Track
 %t    Title             Title
----   ---------------   -------------
 %*    Wildcard          Wildcard
 %%    Per cent sign     Per cent sign
  end

  exit
end

actions = Array.new
options = Array.new
scheme  = '%a - %t'

GetoptLong.new(
  ['--view',       '-v', GetoptLong::NO_ARGUMENT],
  ['--view-tag',   '-t', GetoptLong::REQUIRED_ARGUMENT],
  ['--set-tag',    '-s', GetoptLong::REQUIRED_ARGUMENT],
  ['--remove',     '-r', GetoptLong::NO_ARGUMENT],
  ['--remove-tag', '-d', GetoptLong::REQUIRED_ARGUMENT],
  ['--generate',   '-g', GetoptLong::NO_ARGUMENT],
  ['--rename',     '-m', GetoptLong::NO_ARGUMENT],
  ['--scheme',     '-n', GetoptLong::REQUIRED_ARGUMENT],
  ['--pretend',    '-p', GetoptLong::NO_ARGUMENT],
  ['--list',       '-l', GetoptLong::NO_ARGUMENT],
  ['--help',       '-h', GetoptLong::NO_ARGUMENT]
).each do |option, argument|
  option = option.delete('-').intern

  case option
  when :scheme
    scheme = argument
  when :help, :list, :pretend
    options << option
  when :viewtag, :settag, :removetag
    actions << [option, argument]
  when :generate, :rename
    actions << [option, scheme]
  else
    actions << [option]
  end
end

help if options.include?(:help)
list if options.include?(:list)
help if actions.empty?

if ARGV.empty?
  puts 'No files specified.'
  exit
end

ARGV.each do |file|
  begin
    raise 'File does not exist.' unless File.exist?(file)

    case File.extname(file).downcase
    when '.flac'
      track = FLAC.new(file)
    else
      raise 'File extension not recognised.'
    end

    puts file + ':'

    actions.each do |action|
      track.send(*action)
    end
  rescue RuntimeError => message
    $stderr.puts file + ':'
    $stderr.puts '  ' + message
  end
end