Command Line spotify remote-control (a working example for https://github.com/spotify/web-api/issues/15)

spotify_remote_control.rb

require 'io/console'
require 'open3'
require 'pp'

begin
  require 'coderay'
rescue LoadError # might not already have syntax highlighting
end

class App
  def initialize(stdout, stderr)
    @stdout, @stderr = stdout, stderr
  end

  def tell(message)
    full_message = %'tell application "Spotify"\n  #{message}\nend tell'
    stdout, stderr, status = Open3.capture3 'osascript', '-e', full_message
    @stderr.print stderr unless stderr.empty?
    raise unless status.success?
    stdout
  end
end

class Spotify
  attr_reader :app

  def initialize(app)
    @app = app
  end

  def position(seconds)
    app.tell "set player position to #{seconds}"
  end

  def position_current
    app.tell("get player position").to_i
  end

  def position_relative(seconds)
    position position_current+seconds
  end

  def track_relative(position)
    if 0 < position
      app.tell 'next track'
    elsif position < 0
      app.tell 'previous track'
    end
  end

  def playpause
    app.tell 'playpause'
  end

  def volume_relative(amount)
    app.tell "set sound volume to #{volume+amount}"
  end

  def volume
    app.tell('get sound volume').to_i
  end

  def info
    track_attrs  = ['artist', 'album', 'disc number', 'duration', 'played count', 'track number', 'popularity', 'id', 'name', 'artwork url', 'artwork', 'album artist', 'spotify url']
    player_attrs = ['sound volume', 'player state', 'player position', 'repeating enabled', 'repeating', 'shuffling enabled', 'shuffling']
    results = app.tell [
      *track_attrs.map { |attr| "(get #{attr} of current track)" },
      *player_attrs.map { |attr| "(get #{attr})" },
    ].join(' & "\n" & ')

    lines = results.lines
    { current_track: {
        artist:         lines.shift.chomp,
        album:          lines.shift.chomp,
        disc_number:    lines.shift.to_i,
        duration:       lines.shift.to_i,
        played_count:   lines.shift.to_i,
        track_number:   lines.shift.to_i,
        popularity:     lines.shift.to_i,
        id:             lines.shift.chomp,
        name:           lines.shift.chomp,
        artwork_url:    lines.shift.chomp,
        artwork:        lines.shift.chomp,
        album_artist:   lines.shift.chomp,
        spotify_url:    lines.shift.chomp,
      },
      sound_volume:      lines.shift.to_i,
      player_state:      lines.shift.chomp.intern,
      player_position:   lines.shift.to_f,
      repeat_enabled:    to_bool(lines.shift),
      repeating:         to_bool(lines.shift),
      shuffling_enabled: to_bool(lines.shift),
      shuffling:         to_bool(lines.shift),
    }
  end

  def to_bool(s)
    s = s.chomp
    s == 'true' ? true : s == 'false' ? false : s
  end
end

spotify = Spotify.new(App.new($stdout, $stderr))
key     = nil
loop do
  case key
  when 'q', 3.chr then break
  when 'h'        then spotify.position_relative -1
  when 'H'        then spotify.position_relative -15
  when 'l'        then spotify.position_relative 1
  when 'L'        then spotify.position_relative 15
  when 'j'        then spotify.track_relative 1
  when 'k'        then spotify.track_relative -1
  when 'p'        then spotify.playpause
  when '+'        then spotify.volume_relative 5
  when '-'        then spotify.volume_relative -5
  end
  inspected = spotify.info.pretty_inspect
  inspected = CodeRay.encode(inspected, :ruby, :terminal) if defined? CodeRay
  $stdout.puts "\e[H\e[2J#{inspected}"
  key = $stdin.raw { $stdin.getc }
end