# encoding: UTF-8
require 'bindata'
require 'bindata/itypes'
require 'map'
require 'pathname'
require 'active_support/inflector'

require 'ipod_db/version'

class Hash
  def subset *args
    subset = {}
    args.each do |arg|
      subset[arg] = self[arg] if self.include? arg
    end
    subset
  end
end

class IpodDB
  attr_reader :playback_state

  ExtToFileType = {
    '.mp3' => 1,
    '.aa' => 1,
    '.m4a' => 2,
    '.m4b' => 2,
    '.m4p' => 2,
    '.wav' => 4
  }

  class NotAnIpod < RuntimeError
    def initialize path
      super "#{path} doesn't appear to be an iPod"
    end
  end

  def initialize root_dir
    @root_dir = root_dir
    begin
      read
    rescue Errno::ENOENT
      raise NotAnIpod.new @root_dir
    rescue IOError => error
      puts "Corrupt database, creating a-new"
      init_db
    end
  end

  def IpodDB.looks_like_ipod? path
    Dir.exists? File.join(path,'iPod_Control','iTunes')
  end

  def read
    @playback_state = read_records PState, 'PState'
    stats = read_records Stats, 'Stats'
    sd = read_records SD, 'SD'
    @tracks = Map.new
    stats.records.each_with_index do |stat,i|
      h = stat.snapshot.merge( sd.records[i].snapshot )
      h.delete :reclen
      @tracks[ h[:filename].to_s ] = h
    end
  end

  def init_db
    @playback_state = PState.new
    @tracks = Map.new
  end

  def current_filename
    @tracks.keys[ @playback_state.trackno ]
  end

  def read_records bindata, file_suffix
    File.open make_filename(file_suffix) do |io|
      bindata.read io
    end
  end

  def include? track ; @tracks.include? track ; end

  def update *args
    opts = Map.options(args)
    new_books = opts.getopt :books, default: []
    new_songs = opts.getopt :songs, default: []
    new_tracks = new_books + new_songs
    prev_current_filename = current_filename

    old_tracks = @tracks.keys.clone # clone because otherwise it'll change during iteration
    old_tracks.each do |filename|
      @tracks.delete filename unless new_tracks.include? filename
    end
    old_tracks = @tracks
    @tracks = Map.new
    new_books.each do |filename|
      @tracks[filename] = old_tracks[filename] || {:filename => filename}
      @tracks[filename].merge! shuffleflag: false, bookmarkflag: true
    end
    new_songs.each do |filename|
      @tracks[filename] = old_tracks[filename] || {:filename => filename}
      @tracks[filename].merge! shuffleflag: true, bookmarkflag: false
    end
    if @tracks.include? prev_current_filename
      @playback_state.trackno = @tracks.find_index{|filename,t|filename == prev_current_filename}
    else
      @playback_state.trackno = -1
      @playback_state.trackpos = -1
    end
  end

  def save
    stats = Stats.new
    sd = SD.new
    @tracks.each_value do |track|
      stats.records << track.subset(:bookmarktime, :playcount, :skippedcount)
      sd.records << track.subset(:starttime, :stoptime, :volume, :file_type, :filename,
                                  :shuffleflag, :bookmarkflag)
    end
    write_records @playback_state, 'PState'
    write_records stats, 'Stats'
    write_records sd, 'SD'

    shuffle = make_filename('Shuffle')
    File.delete shuffle if File.exists? shuffle
  end

  def write_records bindata, file_suffix
    File.open( make_filename(file_suffix), 'w' ) do |io|
      bindata.write io
    end
  end

  def each_track
    @tracks.each_value {|track| yield track}
  end

  def each_track_with_index
    @tracks.each_with_index {|path_track,i| yield path_track[1], i}
  end

  def [] filename_or_index
    case filename_or_index
    when Integer
      @tracks.values[filename_or_index]
    else
      @tracks[filename_or_index]
    end
  end

  def inspect
    "<IpodDB>"
  end

  def make_filename suffix
    "#{@root_dir}/iPod_Control/iTunes/iTunes#{suffix}"
  end

  def self.sanitize_filename filename
    ActiveSupport::Inflector.transliterate(filename, '_')
  end

  class PState < BinData::Record
    endian :little
    uint8 :volume, initial_value: 29
    uint24 :shufflepos
    uint24 :trackno, default: -1
    bool24 :shuffleflag
    uint24 :trackpos, default: -1
    string length: 19
  end

  class Stats < BinData::Record
    endian :little
    uint24 :record_count, value: lambda { records.count }
    uint24
    array :records, initial_length: :record_count do
      uint24 :reclen, value: lambda { num_bytes }
      int24 :bookmarktime, initial_value: -1
      string length: 6
      uint24 :playcount
      uint24 :skippedcount
    end
  end

  class SD < BinData::Record
    endian :big
    uint24 :record_count, value: lambda { records.count }
    uint24 :const, value: 0x10800
    uint24 :reclen, value: lambda { num_bytes - records.num_bytes }
    string length: 9
    array :records, initial_length: :record_count do
      uint24 :reclen, value: lambda { num_bytes }
      string length: 3
      uint24 :starttime
      string length: 6
      uint24 :stoptime
      string length: 6
      uint24 :volume, initial_value: 100
      uint24 :file_type, value: lambda { ExtToFileType[File.extname(filename)] }
      string length: 3
      encoded_string :filename, length: 522
      bool8 :shuffleflag
      bool8 :bookmarkflag
      string length: 1
    end
  end
end