app.rb

require 'sinatra'
require 'slim'
require 'coffee-script'
require 'sass'
require 'sequel'

DB = Sequel.sqlite

DB.create_table :uploads do
  String      :id, text: true, primary_key: true
  String      :filename
  Integer     :total_num_chunks
  
  index :id
end

DB.create_table :chunks do
  primary_key :id
  foreign_key :upload_id, :uploads, type: :text
  Integer :number
  
  index [:upload_id, :number]
end

class Chunk < Sequel::Model
  many_to_one :upload
  
  attr_accessor :tempfile
  
  def after_create
    super
    FileUtils.cp tempfile, "uploads/#{upload_id}/#{number}"
  end
end

class Upload < Sequel::Model
  unrestrict_primary_key
  
  one_to_many :chunks
  
  plugin :association_dependencies
  
  add_association_dependencies \
    chunks: :destroy
  
  def done?
    chunks.count == total_num_chunks
  end
  
  def after_create
    super
    FileUtils.mkdir "uploads/#{id}"
  end
  
  def before_destroy
    `ls uploads/#{id} | sort -n | xargs -I {} cat uploads/#{id}/{} > "assets/#{filename}"`
    FileUtils.remove_dir "uploads/#{id}"
    super
  end
end

get '/new' do
  slim :new
end

before '/' do
  @id                 = params[:resumableIdentifier] || halt(415)
  @filename           = params[:resumableFilename]
  
  @chunk_number       = params[:resumableChunkNumber].to_i
  @chunk_size         = params[:resumableChunkSize].to_i
  @total_size         = params[:resumableTotalSize].to_i
  @total_num_chunks   = (@total_size / @chunk_size).ceil + 1
  
  @upload = Upload.find_or_create(
    id:               @id, 
    filename:         @filename, 
    total_num_chunks: @total_num_chunks
  )
end

get '/' do
  not_found unless @upload.chunks_dataset.first(number: @chunk_number)
end

post '/' do
  @upload.add_chunk(number: @chunk_number, tempfile: params[:file][:tempfile])
  @upload.destroy if @upload.done?
  200
end

__END__
@@ layout
html
head
  script src='//ajax.googleapis.com/ajax/libs/jquery/1.7.0/jquery.min.js'
  script src='/js/resumable.js'
  
  sass:
    .drop
      width: 50%
      margin
        left: auto
        right: auto
      height: 50%
      background-color: lightgrey
      border: 5px dashed grey
      position: relative
      .progress
        width: 100%
        background-color: green
        position: absolute
        bottom: 0
      
body
  == yield
  
  coffee:
    r = new Resumable()
    r.assignDrop $('.drop')

    r.on 'fileAdded', (file) ->
      r.upload()

    r.on 'fileSuccess', (file, message) ->
      r.removeFile(file)

    r.on 'fileError', (file, message) ->
      $('.progress').css('background-color', 'red')
      r.removeFile(file)
      
    r.on 'fileProgress', (file) ->
      $('.progress').css('height', "#{r.progress() * 100}%")
  
@@ new
.drop 
  Drop here
  .progress