FlashSessionCookieMiddleware with fix for sessions with url encoded tokens

flash_session_cookie_middleware.rb

# FlashSessionCookieMiddleware
#   passing your session in the URI, when it should be in the cookie
# 
#
# By Bert Goethals: (https://www.twitter.com/bertgoethals)
# Based on code by Rob Anderton (http://thewebfellas.com/blog/2008/12/22/flash-uploaders-rails-cookie-based-sessions-and-csrf-rack-middleware-to-the-rescue)
#
# This code has no licence what so ever, you are free to use it how you want, as
#   long as you don't blame me when your code breaks.
#
# This code only works in following cases:
# - passing the session as the variable for 'session_key' (it is best to set this to your app's session cookie name
# - the value is URI escaped once, (don't do it explicetally if using rails helpers, they do it for you)
# - Loading this middleware before session_store middleware
#
# Note, this could work also after session_store middleware (or others).
# However, these could already have modified the cooky values, and this module
# could become unstable because of that, and it's functioning can not be
# guaranteed.
#

require 'rack/utils'

class FlashSessionCookieMiddleware
  def initialize(app, session_key = '_session_id')
    @app = app
    @session_key = session_key
  end

  # Imagine the session_key value being:
  # => "ABC+123"
  # The session in the URL is url encoded:
  # => "ABC%B2123"
  # after ::Rack::Utils our params[@session_key] is:
  # => "ABC+123"
  # this is NOT expected behaviour!!!
  # When the session store is running trough the cookie it will escape the
  # cookie values. See lib/rack/request.rb (Rack gem) in the cookie method:
  # => "ABC 123"
  #
  # So we are supposed to put the escaped value in the cookie.
  #
  def call(env)
    if env['HTTP_USER_AGENT'] =~ /^(Adobe|Shockwave) Flash/
      params = ::Rack::Utils.parse_query(env['QUERY_STRING'])
      env['HTTP_COOKIE'] = [ @session_key, ::Rack::Utils.escape(params[@session_key]) ].join('=').freeze unless params[@session_key].nil?
    end
    @app.call(env)
  end

end

Dear Bert!
Thank you very much!
I spend half a day while solving same issue and playing with those escape/unescape combinations.
Your solution works for me. You saved my second half of a day! ))))) My Best Good Wishes to you!
Pavel

p.s. In our config we use POST params to send session.
In SWFUpload config script:
post_params : {
"target_element_id" : "<%=@element.id%>",
"<%= SYSTEM_SESSION_KEY%>" : "<%=CGI::escape(cookies[SYSTEM_SESSION_KEY])%>"
},
and we use this code to parse it in rails:
params = ::Rack::Request.new(env).params