app.rb

require 'sinatra/base'
require 'sinatra/flash'

Encoding.default_internal = 'utf-8'
Encoding.default_external = 'utf-8'

class Spotyt < Sinatra::Base
  enable :sessions
  register Sinatra::Flash

  ###############
  # => Config!  #
  ###############
  set :session_secret, 'ADD_YOUR_OWN_SECRET_HERE'
  @@redis = Redis.new(thread_safe: true)

  ###############
  # => Methods! #
  ###############
  # Gets Track Metadata from Spotify's Web Metadata API
  def get_track(spotify_id)
    content = HTTParty.get('http://ws.spotify.com/lookup/1/.json?uri=' + URI.escape("spotify:track:#{spotify_id}"))
    if !content.body.empty?
      Oj.load(content.body)
    else
      flash[:notice] = 'Error with Spotify! Try again in 10 seconds!'
    end
  end

  # Finds the song on youtube
  # It does this by searching in format "Song Name - Artist" on youtube
  # Then it parses the XML data with nokogiri and picks the first video
  def youtube
    download = HTTParty.get("https://gdata.youtube.com/feeds/api/videos?q=#{URI.escape(@track)}")
    if !download.body.empty?
      doc = Nokogiri::HTML(download.body)
      vids = doc.xpath('//link[contains(@href, "https://www.youtube.com/watch")]').to_a
      video = vids.first
      # Extracting the Video-ID
      if video
        query_string = URI.parse(video['href']).query
        Hash[URI.decode_www_form(query_string)]
      else
        "Can't find a decent YouTube mirror."
      end
    else
      flash[:notice] = 'Error with Youtube! Try again in 30 seconds!'
    end
  end

  def latest
    	@latest = @@redis.lrange('tracks', 0, 9)
  end

  # This method extracts the spotify track ID if the URI/URL is in the correct format
  # If it isn't then it returns false
  def extract_spotify_id(query)
    if query.start_with?('http://open.spotify.com/track/', 'https://open.spotify.com/track/', 'https://play.spotify.com/track/', 'http://play.spotify.com/track/')
      URI.split(query)[5].split('/')[2]
    elsif query.start_with?('spotify:track:')
      query.split(':')[2]
    else
      false
    end
  end

  ###########################
  # => Routes & Controllers #
  ###########################
  get '/' do

    latest

    haml :index
  end

  get '/fetch' do
    # Cache the page for 30 mins (mainly to reduce load on Redis since we can only have 10 max connections on the free plan)
    cache_control :public, max_age: 1800

    latest

    # Extracts the querys and then checks if the query is in the correct format.
    query = params[:query]
    @spotify_id = extract_spotify_id(query)
    if @spotify_id
      # If it is in the correct format it searches that query in Redis
      # If redis returns false (nil) then it goes ahead and makes requests to Spotify and Youtube
      redis_q = @@redis.get(@spotify_id)
      if !redis_q
        spotify = get_track(@spotify_id)['track']

        @track = "#{spotify["name"]} - #{spotify["artists"][0]["name"]}"

        @video_id = youtube

        if !@video_id.include?("Can't find a decent YouTube mirror.")
          @video_id = youtube['v']
          # Caching results in redis
          result = Oj.dump(track: @track, video_id: @video_id)
          @@redis.pipelined do
            @@redis.set(@spotify_id, result)
            # Creates a list of tracks converted so we can create the latest 10 converts leaderboard
            @@redis.lpush('tracks', "#{@track}::#{@spotify_id}")
          end
        else
          @track = nil
          @video_id = nil
          flash[:notice] = "Can't find a decent YouTube mirror."
        end
      else
        # If the video has already been converted then it loads the data from redis and throws up the results
        result = Oj.load(redis_q)
        @track = result[:track]
        @video_id = result[:video_id]

      end
    else
      flash[:notice] = 'Incorrect URI or URL! Try again!'
      redirect '/'
    end
    haml :index
  end

  # This is an API which does exactly the same as above but returns json
  # The format of the url is slightly different as you can probably tell
  # The format is:
  # http://www.spotify2tube.com/fetch/http://open.spotify.com/track/0pjjdauz55YnSJ8OsQKI3P
  #  or
  # http://www.spotify2tube.com/fetch/spotify:track:5ZdzNVOmCSp5HFLk0EgvJS
  get '/fetch/*' do
    content_type :json
    # Cache the page for 30 mins
    cache_control :public, max_age: 1800

    # Extracts the querys and then checks if the query is in the correct format
    query = params[:splat][0].gsub(':/', '://')
    @spotify_id = extract_spotify_id(query)
    if @spotify_id
      # If it is in the correct format it searches that query in Redis
      # If redis returns false (nil) then it goes ahead and makes requests to Spotify and Youtube
      redis_q = @@redis.get(@spotify_id)
      if !redis_q
        spotify = get_track(@spotify_id)['track']

        @track = "#{spotify["name"]} - #{spotify["artists"][0]["name"]}"

        @video_id = youtube
        if !@video_id.include?("Can't find a decent YouTube mirror.")
          @video_id = youtube['v']
          # Caching results in redis
          result = Oj.dump(track: @track, video_id: @video_id)
          @@redis.pipelined do
            @@redis.set(@spotify_id, result)
            # Creates a list of tracks converted so we can create the latest 10 converts leaderboard
            @@redis.lpush('tracks', "#{@track}::#{@spotify_id}")
          end
          Oj.dump(
            spotify_id: @spotify_id,
            track: @track,
            youtube_video_id: @video_id,
            youtube_url: "https://www.youtube.com/watch?v=#{@video_id}",
            spotify2tube_url: "#{request.base_url}/fetch?query=spotify:track:#{@spotify_id}"
          )
        else
          @track = nil
          @video_id = nil
          Oj.dump(
            error: "Can't find a decent YouTube mirror."
          )
        end
      else
        # If the video has already been converted then it loads the data from redis and throws up the results
        result = Oj.load(redis_q)
        @track = result[:track]
        @video_id = result[:video_id]
        Oj.dump(
          spotify_id: @spotify_id,
          track: @track,
          youtube_video_id: @video_id,
          youtube_url: "https://www.youtube.com/watch?v=#{@video_id}",
          spotify2tube_url: "#{request.base_url}/fetch?query=spotify:track:#{@spotify_id}"
        )
      end
    else
      Oj.dump(error: 'Incorrect URI or URL! Try again!')
    end
  end

  get '/sitemap.xml' do
    # Cache the page for 0.5 days
    cache_control :public, max_age: 43_200
    links = @@redis.lrange("tracks", 0, -1)

    map = XmlSitemap::Map.new('www.spotify2tube.com') do |m|
      m.add(url: '/', period: :daily, priority: 1.0)
      links.each do |link|
        link = link.split('::')
        m.add(url: "#{request.base_url}/fetch?query=spotify:track:#{URI.escape(link[1])}", period: :weekly, priority: 0.5)
      end
    end

    headers['Content-Type'] = 'text/xml'
    map.render
  end
end