app.rb

require 'base64'
require 'securerandom'
require 'erb'
require 'tmpdir'
require 'sinatra'
require 'sinatra/streaming'
require 'tempfile'

configure do
	use Rack::Session::Cookie, :secret => "some unique secret string here"
	enable :sessions
end

get '/' do 
	csrf = (session['csrf'] ||= SecureRandom.hex)
	presets = Dir.glob('./presets/*.sts').map {|m| File.basename(m, '.sts')}
	erb :index, :locals => { :presets => presets, :csrf => csrf }
end

def check_csrf
	raise 'Incorrect CSRF' if params['csrf'] != session['csrf'] or session['csrf'] == nil
end

post '/download/' do 
	
	check_csrf

	content_type 'audio/flac'

	final = Tempfile.new('sts', Dir.tmpdir)
	final.close
	
	raise 'Invalid file' if !params[:file][:filename]

	file_name = params[:file][:filename]
	ext = File.extname(file_name)

	file_name = File.basename(file_name, ext)

	raise 'Invalid extension' unless ['mp3', 'flac', 'wav', 'ogg'].include?(ext[1..-1])

	preset = params[:preset]
	preset_path = './presets/' + preset + '.sts'
	raise 'Invalid preset' unless preset.match(/^[a-zA-Z0-9\_]+$/) and File.exist?(preset_path)

	key = ENV['ST_KEY'] ? ' -k "' + ENV['ST_KEY'] + '"' : ''

	`avconv -i "#{params[:file][:tempfile].path}" -f wav -acodec pcm_s16le -ac 2 - | stereo_tool_cmd#{key} - - -s #{preset} | avconv -i - -c:a flac -f flac -y #{final.path}`

	puts 'Calling send_file on #{final.path}'
	
	send_file final.path, { :disposition => 'attachment', :filename => "#{file_name}.processed.flac", :type => 'flac' }
	#redirect "/file/" + File.basename(final.path) + "?fn=" + Base64::urlsafe_encode64(file_name)

end

get '/file/:file' do | file |
		
	next if file[0..2] != "sts" or file.include? "/"
	file_name = Base64::urlsafe_decode64(params[:fn]) rescue "untitled"
	
	send_file Dir.tmpdir + "/" + file, { :disposition => 'attachment', :filename => file_name + ".processed.flac", :type => 'flac' }
	
end

Thread.new do | a |

	loop do
	
		Dir.glob(Dir.tmpdir + "/sts*").each do | path |
			data = `lsof #{path}`
			next if data.to_s.length > 5
			# The file isn't being read, we can close it
			sleep 5
			puts "Re-checking #{path}"
			data = `lsof #{path}`
			next if data.to_s.length > 5
			puts "File hasn't been opened in the past 5 seconds, likely clean-up able"
		
			File.unlink(path)
		end
		sleep 5

	end
end