#!/usr/bin/env ruby
# frozen_string_literal: true

require 'pathname'
require 'open3'

# Renames music files in a directory according to the file's tags.
# Expects two arguments:
# - Path to the zip file with music files.
# - Music directory to extract songs into.

class Song
  attr_reader :title, :track, :extension

  def initialize(extension)
    @extension = extension
  end

  def title=(title)
    @title = title.strip
  end

  def track=(track)
    @track = track.strip.split('/').first.rjust(2, '0')
  end

  def to_s
    @track + ' - ' + @title + @extension
  end
end

def find_unnamed_directory(parent_path)
  parent_path.children.filter { |child| child.basename.to_s.start_with? '_' }.first
end

def extract_and_rename_archive(album_archive, music_directory)
  artist_name, album_name = album_archive.basename('.zip').to_s.split(' - ')

  system 'unzip', '-d', music_directory.to_path, album_archive.to_path, exception: true

  artist_path = music_directory + artist_name
  album_path = artist_path + album_name
  source_artist_path = find_unnamed_directory music_directory

  if artist_path.exist?
    find_unnamed_directory(source_artist_path).rename album_path
    source_artist_path.unlink
  else
    source_artist_path.rename artist_path
    find_unnamed_directory(artist_path).rename album_path
  end
  album_path
end

def probe_song(song_path)
  song = Song.new song_path.extname

  Open3.popen3 'ffprobe', song_path.to_s do |_stdin, _stdout, stderr, _wait_pid|
    while (line = stderr.gets)
      key, value = line.split ':'
      next if value.nil?

      case key.strip.downcase
      when 'title'
        song.title = value if song.title.nil?
      when 'track'
        song.track = value if song.track.nil?
      end
    end
  end
  song
end

album_archive = Pathname.new ARGV[0]
music_directory = Pathname.new ARGV[1]
metadata = {}

album_path = extract_and_rename_archive album_archive, music_directory

Dir.each_child album_path do |filename|
  song_path = album_path + filename

  metadata[song_path] = probe_song(song_path).to_s
end

metadata.each_pair do |from, to|
  File.rename(from, album_path + to)
end