audios_controller.rb

module Api
  module V1
    class AudiosController < ApplicationController

      def create

        return render json: { error: 'File format error.' } unless file_exist? && mp3_exist?
        return render json: { error: 'Request format error.' } unless artist_exist? && song_exist?

        audio = Audio.new audio_params
        audio.save!

        original_path = audio_path 'original', audio
        clone_path = audio_path '128kbps', audio

        save_original original_path
        save_clone original_path, clone_path

        render json: { track_id: audio.id }
      end

      protected

      # Saving the original into a separate folder
      def save_original original_path
        File.open(original_path, 'wb') { |f| f.write(params[:file].read) }
      end

      # Saving the clone with a lower bitrate into a separate folder
      def save_clone original_path, clone_path
        `avconv -i #{ original_path } -c:a libmp3lame -b:a 128k #{ clone_path }`
      end

      # Generates a path for saving files
      def audio_path additional_path, audio
        File.join 'public', 'audio', additional_path, audio.id.to_s +
        '_' + audio.artist.gsub(' ', '_') +
        '_' + audio.song.gsub(' ', '_') + '.mp3'
      end

      # Checks file existance in the request
      def file_exist?
        params[:file]
      end

      # Checks mp3 extension existance in the request
      def mp3_exist?
        params[:file].original_filename.split('.').last == 'mp3'
      end

      # Checks artist existance in the request
      def artist_exist?
        params[:artist]
      end

      # Checks song existance in the request
      def song_exist?
        params[:song]
      end

      private

      # Permitted attributes
      def audio_params
        params.permit(:file, :artist, :song)
      end
    end
  end
end