module CASClient
  module Frameworks
    module Rails
      class Filter
        cattr_reader :config, :log, :client
        
        # These are initialized when you call configure.
        @@config = nil
        @@client = nil
        @@log = nil
        @@fake_user = nil
        @@fake_extra_attributes = nil
        
        class << self
          def filter(controller)
            raise "Cannot use the CASClient filter because it has not yet been configured." if config.nil?
            
            if @@fake_user
              controller.session[client.username_session_key] = @@fake_user
              controller.session[:casfilteruser] = @@fake_user
              controller.session[client.extra_attributes_session_key] = @@fake_extra_attributes
              return true
            end
            
            
            last_st = controller.session[:cas_last_valid_ticket]
            
            if single_sign_out(controller)
              controller.send(:render, :text => "CAS Single-Sign-Out request intercepted.")
              return false 
            end

            st = read_ticket(controller)
            
            is_new_session = true
            
            if st && last_st && 
                last_st.ticket == st.ticket && 
                last_st.service == st.service
              # warn() rather than info() because we really shouldn't be re-validating the same ticket. 
              # The only situation where this is acceptable is if the user manually does a refresh and 
              # the same ticket happens to be in the URL.
              log.warn("Re-using previously validated ticket since the ticket id and service are the same.")
              st = last_st
              is_new_session = false
            elsif last_st &&
                !config[:authenticate_on_every_request] && 
                controller.session[client.username_session_key]
              # Re-use the previous ticket if the user already has a local CAS session (i.e. if they were already
              # previously authenticated for this service). This is to prevent redirection to the CAS server on every
              # request.
              #
              # This behaviour can be disabled (so that every request is routed through the CAS server) by setting
              # the :authenticate_on_every_request config option to true. However, this is not desirable since
              # it will almost certainly break POST request, AJAX calls, etc.
              log.debug "Existing local CAS session detected for #{controller.session[client.username_session_key].inspect}. "+
                "Previous ticket #{last_st.ticket.inspect} will be re-used."
              st = last_st
              is_new_session = false
            end
            
            if st
              client.validate_service_ticket(st) unless st.has_been_validated?
              vr = st.response
              
              if st.is_valid?
                if is_new_session
                  log.info("Ticket #{st.ticket.inspect} for service #{st.service.inspect} belonging to user #{vr.user.inspect} is VALID.")
                  controller.session[client.username_session_key] = vr.user.dup
                  controller.session[client.extra_attributes_session_key] = HashWithIndifferentAccess.new(vr.extra_attributes) if vr.extra_attributes
                  
                  if vr.extra_attributes
                    log.debug("Extra user attributes provided along with ticket #{st.ticket.inspect}: #{vr.extra_attributes.inspect}.")
                  end
                  
                  # RubyCAS-Client 1.x used :casfilteruser as it's username session key,
                  # so we need to set this here to ensure compatibility with configurations
                  # built around the old client.
                  controller.session[:casfilteruser] = vr.user
                  
                  if config[:enable_single_sign_out]
                    f = store_service_session_lookup(st, controller.request.session_options[:id] || controller.session.session_id)
                    log.debug("Wrote service session lookup file to #{f.inspect} with session id #{controller.request.session_options[:id] || controller.session.session_id.inspect}.")
                  end
                end
              
                # Store the ticket in the session to avoid re-validating the same service
                # ticket with the CAS server.
                controller.session[:cas_last_valid_ticket] = st
                
                if vr.pgt_iou
                  unless controller.session[:cas_pgt] && controller.session[:cas_pgt].ticket && controller.session[:cas_pgt].iou == vr.pgt_iou
                    log.info("Receipt has a proxy-granting ticket IOU. Attempting to retrieve the proxy-granting ticket...")
                    pgt = client.retrieve_proxy_granting_ticket(vr.pgt_iou)

                    if pgt
                      log.debug("Got PGT #{pgt.ticket.inspect} for PGT IOU #{pgt.iou.inspect}. This will be stored in the session.")
                      controller.session[:cas_pgt] = pgt
                      # For backwards compatibility with RubyCAS-Client 1.x configurations...
                      controller.session[:casfilterpgt] = pgt
                    else
                      log.error("Failed to retrieve a PGT for PGT IOU #{vr.pgt_iou}!")
                    end
                  else
                    log.info("PGT is present in session and PGT IOU #{vr.pgt_iou} matches the saved PGT IOU.  Not retrieving new PGT.")
                  end

                end
                
                return true
              else
                log.warn("Ticket #{st.ticket.inspect} failed validation -- #{vr.failure_code}: #{vr.failure_message}")
                unauthorized!(controller, vr)
                return false
              end
            else # no service ticket was present in the request
              if returning_from_gateway?(controller)
                log.info "Returning from CAS gateway without authentication."

                # unset, to allow for the next request to be authenticated if necessary
                controller.session[:cas_sent_to_gateway] = false

                if use_gatewaying?
                  log.info "This CAS client is configured to use gatewaying, so we will permit the user to continue without authentication."
                  controller.session[client.username_session_key] = nil
                  return true
                else
                  log.warn "The CAS client is NOT configured to allow gatewaying, yet this request was gatewayed. Something is not right!"
                end
              end
              
              unauthorized!(controller)
              return false
            end
          rescue OpenSSL::SSL::SSLError
            log.error("SSL Error: hostname was not match with the server certificate. You can try to disable the ssl verification with a :force_ssl_verification => false in your configurations file.")
            unauthorized!(controller)
            return false
          end
          
          def configure(config)
            @@config = config
            @@config[:logger] = RAILS_DEFAULT_LOGGER unless @@config[:logger]
            @@client = CASClient::Client.new(config)
            @@log = client.log
          end
          
          # used to allow faking for testing
          # with cucumber and other tools.
          # use like 
          #  CASClient::Frameworks::Rails::Filter.fake("homer")
          # you can also fake extra attributes by including a second parameter
          #  CASClient::Frameworks::Rails::Filter.fake("homer", {:roles => ['dad', 'husband']})
          def fake(username, extra_attributes = nil)
            @@fake_user = username
            @@fake_extra_attributes = extra_attributes
          end
          
          def use_gatewaying?
            @@config[:use_gatewaying]
          end
          
          # Returns the login URL for the current controller. 
          # Useful when you want to provide a "Login" link in a GatewayFilter'ed
          # action. 
          def login_url(controller)
            service_url = read_service_url(controller)
            url = client.add_service_to_login_url(service_url)
            log.debug("Generated login url: #{url}")
            return url
          end

          # allow controllers to reuse the existing config to auto-login to
          # the service
          # 
          # Use this from within a controller. Pass the controller, the
          # login-credentials and the path that you want the user
          # resdirected to on success.
          #
          # When writing a login-action you must check the return-value of
          # the response to see if it failed!
          #
          # If it worked - you need to redirect the user to the service -
          # path, because that has the ticket that will *actually* log them
          # into your system
          #
          # example:
          # def autologin
          #   resp = CASClient::Frameworks::Rails::Filter.login_to_service(self, credentials, dashboard_url)
          #   if resp.is_faiulure?
          #     flash[:error] = 'Login failed'
          #     render :action => 'login'
          #   else
          #     return redirect_to(@resp.service_redirect_url)
          #   end
          # end
          def login_to_service(controller, credentials, return_path)
            resp = @@client.login_to_service(credentials, return_path)
            if resp.is_failure?
              log.info("Validation failed for service #{return_path.inspect} reason: '#{resp.failure_message}'")
            else
              log.info("Ticket #{resp.ticket.inspect} for service #{return_path.inspect} is VALID.")
            end
            
            resp
          end
          
          # Clears the given controller's local Rails session, does some local 
          # CAS cleanup, and redirects to the CAS logout page. Additionally, the
          # <tt>request.referer</tt> value from the <tt>controller</tt> instance 
          # is passed to the CAS server as a 'destination' parameter. This 
          # allows RubyCAS server to provide a follow-up login page allowing
          # the user to log back in to the service they just logged out from 
          # using a different username and password. Other CAS server 
          # implemenations may use this 'destination' parameter in different 
          # ways. 
          # If given, the optional <tt>service</tt> URL overrides 
          # <tt>request.referer</tt>.
          def logout(controller, service = nil)
            referer = service || controller.request.referer
            st = controller.session[:cas_last_valid_ticket]
            delete_service_session_lookup(st) if st
            controller.send(:reset_session)
            controller.send(:redirect_to, client.logout_url(referer))
          end
          
          def unauthorized!(controller, vr = nil)
            if controller.params[:format] == "xml"
              if vr
                controller.send(:render, :xml => "<errors><error>#{vr.failure_message}</error></errors>", :status => 401)
              else
                controller.send(:head, 401)
              end
            else
              redirect_to_cas_for_authentication(controller)
            end
          end
          
          def redirect_to_cas_for_authentication(controller)
            redirect_url = login_url(controller)
            
            if use_gatewaying?
              controller.session[:cas_sent_to_gateway] = true
              redirect_url << "&gateway=true"
            else
              controller.session[:cas_sent_to_gateway] = false
            end
            
            if controller.session[:previous_redirect_to_cas] &&
                controller.session[:previous_redirect_to_cas] > (Time.now - 1.second)
              log.warn("Previous redirect to the CAS server was less than a second ago. The client at #{controller.request.remote_ip.inspect} may be stuck in a redirection loop!")
              controller.session[:cas_validation_retry_count] ||= 0
              
              if controller.session[:cas_validation_retry_count] > 3
                log.error("Redirection loop intercepted. Client at #{controller.request.remote_ip.inspect} will be redirected back to login page and forced to renew authentication.")
                redirect_url += "&renew=1&redirection_loop_intercepted=1"
              end
              
              controller.session[:cas_validation_retry_count] += 1
            else
              controller.session[:cas_validation_retry_count] = 0
            end
            controller.session[:previous_redirect_to_cas] = Time.now
            
            log.debug("Redirecting to #{redirect_url.inspect}")
            controller.send(:redirect_to, redirect_url)
          end
          
          private
          def single_sign_out(controller)
            
            # Avoid calling raw_post (which may consume the post body) if
            # this seems to be a file upload
            if content_type = controller.request.headers["CONTENT_TYPE"] &&
                content_type =~ %r{^multipart/}
              return false
            end
            
            if controller.request.post? &&
                controller.params['logoutRequest'] &&
                controller.params['logoutRequest'] =~
                  %r{^<samlp:LogoutRequest.*?<samlp:SessionIndex>(.*)</samlp:SessionIndex>}m
              # TODO: Maybe check that the request came from the registered CAS server? Although this might be
              #       pointless since it's easily spoofable...
              si = $~[1]
              
              unless config[:enable_single_sign_out]
                log.warn "Ignoring single-sign-out request for CAS session #{si.inspect} because ssout functionality is not enabled (see the :enable_single_sign_out config option)."
                return false
              end
              
              log.debug "Intercepted single-sign-out request for CAS session #{si.inspect}."
              
              begin
                required_sess_store = ActiveRecord::SessionStore
                current_sess_store  = ActionController::Base.session_store
              rescue NameError
                # for older versions of Rails (prior to 2.3)
                required_sess_store = CGI::Session::ActiveRecordStore
                current_sess_store  = ActionController::Base.session_options[:database_manager]
              end


              if current_sess_store == required_sess_store
                session_id = read_service_session_lookup(si)

                if session_id
                  session = current_sess_store::Session.find_by_session_id(session_id)
                  if session
                    session.destroy
                    log.debug("Destroyed #{session.inspect} for session #{session_id.inspect} corresponding to service ticket #{si.inspect}.")
                  else
                    log.debug("Data for session #{session_id.inspect} was not found. It may have already been cleared by a local CAS logout request.")
                  end
                  
                  log.info("Single-sign-out for session #{session_id.inspect} completed successfuly.")
                else
                  log.warn("Couldn't destroy session with SessionIndex #{si} because no corresponding session id could be looked up.")
                end
              else
                log.error "Cannot process logout request because this Rails application's session store is "+
                  " #{current_sess_store.name.inspect}. Single Sign-Out only works with the "+
                  " #{required_sess_store.name.inspect} session store."
              end
              
              # Return true to indicate that a single-sign-out request was detected
              # and that further processing of the request is unnecessary.
              return true
            end
            
            # This is not a single-sign-out request.
            return false
          end
          
          def read_ticket(controller)
            ticket = controller.params[:ticket]
            
            return nil unless ticket
            
            log.debug("Request contains ticket #{ticket.inspect}.")
            
            if ticket =~ /^PT-/
              ProxyTicket.new(ticket, read_service_url(controller), controller.params[:renew])
            else
              ServiceTicket.new(ticket, read_service_url(controller), controller.params[:renew])
            end
          end
          
          def returning_from_gateway?(controller)
            controller.session[:cas_sent_to_gateway]
          end
          
          def read_service_url(controller)
            if config[:service_url]
              log.debug("Using explicitly set service url: #{config[:service_url]}")
              return config[:service_url]
            end
            
            params = controller.params.dup
            params.delete(:ticket)
            service_url = controller.url_for(params)
            log.debug("Guessed service url: #{service_url.inspect}")
            return service_url
          end
          
          # Creates a file in tmp/sessions linking a SessionTicket
          # with the local Rails session id. The file is named
          # cas_sess.<session ticket> and its text contents is the corresponding 
          # Rails session id.
          # Returns the filename of the lookup file created.
          def store_service_session_lookup(st, sid)
            st = st.ticket if st.kind_of? ServiceTicket
            f = File.new(filename_of_service_session_lookup(st), 'w')
            f.write(sid)
            f.close
            return f.path
          end
          
          # Returns the local Rails session ID corresponding to the given
          # ServiceTicket. This is done by reading the contents of the
          # cas_sess.<session ticket> file created in a prior call to 
          # #store_service_session_lookup.
          def read_service_session_lookup(st)
            st = st.ticket if st.kind_of? ServiceTicket
            ssl_filename = filename_of_service_session_lookup(st)
            return File.exists?(ssl_filename) && IO.read(ssl_filename)
          end
          
          # Removes a stored relationship between a ServiceTicket and a local
          # Rails session id. This should be called when the session is being
          # closed.
          #
          # See #store_service_session_lookup.
          def delete_service_session_lookup(st)
            st = st.ticket if st.kind_of? ServiceTicket
            ssl_filename = filename_of_service_session_lookup(st)
            File.delete(ssl_filename) if File.exists?(ssl_filename)
          end
          
          # Returns the path and filename of the service session lookup file.
          def filename_of_service_session_lookup(st)
            st = st.ticket if st.kind_of? ServiceTicket
            return "#{RAILS_ROOT}/tmp/sessions/cas_sess.#{st}"
          end
        end
      end
    
      class GatewayFilter < Filter
        def self.use_gatewaying?
          return true unless @@config[:use_gatewaying] == false
        end
      end
    end
  end
end