module Metry
  module Rack
    class Tracking
      COOKIE = "_metry"

      def initialize(app)
        @app = app
      end
    
      def call(env)
        request = ::Rack::Request.new(env)
        env["metry.event"] = event = build_event(request)
        env["metry.visitor"] = visitor = find_or_create_visitor(request)

        status, headers, body = @app.call(env)

        response = ::Rack::Response.new(body, status, headers)

        save_visitor(response, visitor)

        unless event.ignore?
          event.visitor = visitor
          event.status = status.to_s
          event.save
        end

        response.to_a
      end
    
      def build_event(request)
        Event.new("event" => "pageview",
          :path => request.fullpath,
          :ip => request.ip,
          :host => request.host,
          :method => request.request_method,
          :referrer => request.env["HTTP_REFERER"],
          :user_agent => request.env["HTTP_USER_AGENT"])
      end
    
      def find_or_create_visitor(request)
        visitor = nil
        if id = request.cookies[COOKIE]
          begin
            visitor = Visitor.find(id)
          rescue MongoMapper::IllegalID, MongoMapper::DocumentNotFound
            visitor = nil
          end
        end
        (visitor || Visitor.create)
      end
    
      def save_visitor(response, visitor)
        visitor.save
        response.set_cookie(COOKIE,
          :value => visitor.id.to_s,
          :expires => (Time.now+(60*60*24*365*20)),
          :path => '/')
      end
    end
  end
end