module Merb
  
  module SessionMixin

    def setup_session
      MERB_LOGGER.info("Setting up session")
      before = cookies[session_id_key]
      @session , cookies[session_id_key] = Merb::MemorySession.persist(cookies[session_id_key])
      @_new_cookie = cookies[session_id_key] != before
    end

    def finalize_session
      MERB_LOGGER.info("Finalize session")
      set_cookie(session_id_key, cookies[session_id_key], Time.now+Merb::Const::WEEK*2) if @_new_cookie
    end 

  end
  
  class MemorySession
        
    class << self
  
      RAND_CHARS = [*'A'..'Z'] + [*'0'..'9'] + [*'a'..'z']

      # Generates a new session ID and creates a row for the new session in the database.
      def generate
        rand_max = RAND_CHARS.size
        sid = (0...32).inject("") { |ret,_| ret << RAND_CHARS[rand(rand_max)] }
        [create(:session_id => sid, :data => {}), sid]
      end
      
      # Gets the existing session based on the <tt>session_id</tt> available in cookies.
      # If none is found, generates a new session.
      def persist(session_id)
        if session_id
          session = self[session_id]
          sid = session_id
        end
        unless session
          session, sid = generate
        end
        [session, sid]
      end
      
      def setup(opts={})
        @opts = opts
        @sessions = Hash.new
        @timestamps = Hash.new
        @mutex = Mutex.new
        @session_ttl = opts.fetch(:session_ttl, 60*60) # default 1 hour
        start_timer
        self
      end
      
      def create(opts={})
        self[opts[:session_id]] = opts[:data]
      end  
      
      def [](key)
        @mutex.synchronize {
          @timestamps[key] = Time.now
          @sessions[key]
        }
      end  
       
      def []=(key, val) 
        @mutex.synchronize {
          @timestamps[key] = Time.now
          @sessions[key] = val
        } 
      end
      
      def delete(key)
        @mutex.synchronize {
          @sessions.delete(key)
        }
      end
      
      def reap_old_sessions
        @timestamps.each do |key,stamp|
          if stamp + @session_ttl < Time.now
            delete(key)
          end  
        end
        GC.start
      end  
      
      def start_timer
        Thread.new do
          loop {
            sleep @session_ttl
            reap_old_sessions
          } 
        end  
      end  
      
      def sessions
        @sessions
      end  
  
    end # end singleton class
    
  end # end DRbSession

end