mpd_musicinfo.rb

#!/usr/bin/env ruby
# frozen_string_literal: true
# rubocop:disable all

require "json"
require "active_support/core_ext/hash/keys"

FORMAT = "    |    Now Playing:  %{title}  by  %{artist}  in  %{album}"

module MPD
  class TrackInfo
    DEFAULT_INFO = {
      artist: "Unknown Artist",
      album: "Unknown Album",
      title: "Unknown Title"
    }.freeze

    attr_reader :info

    def initialize(hash = {})
      tmp = hash.symbolize_keys.reject { |_,v| v.empty? }
      @info = DEFAULT_INFO.dup.update(tmp)
    end

    def to_s
      @info.values.join(" - ")
    end

    def format(fmt)
      Kernel.format(fmt, **@info)
    end

    def ==(other)
      return false unless other.is_a?(self.class)
      return info == other.info
    end

    def none?
      @info[:title] == "Unknown Title"
    end
  end

module_function

  def info
    fmt = %{'{"artist":"%artist%","album":"%album%","title":"%title%"}'}
    lines = `mpc -f #{fmt} status`.chomp.lines
    return [TrackInfo.new({}), false] if lines.size < 3
    [TrackInfo.new(JSON.parse(lines.first)), /^\[playing\]/.match?(lines[1])]
  end
end

previous = MPD::TrackInfo.new
outfile  = ARGV.first
cleared  = false

loop do
  current, playing = MPD.info

  if (current.none? || !playing) && !cleared
    puts "Clearing song info"
    File.open(outfile, "w") { |f| f.write("") }
    cleared = true
  elsif previous != current
    puts "Changing song to #{current}"
    File.open(outfile, "w") { |f| f.write(current.format(FORMAT)) }
    previous = current.dup
    cleared = false
  end

  sleep(2)
end