refactor: let handlers check if they are applicable

Instead of testing the preconditions for each handler in the dispatcher
the dispatcher hands a request to one handler after the other until one of
them responds.

This is similar to the Chain of Responsibility patter but we iterate over the
'handler_chain' array instead of a linked list.

To change the order of handlers or add other handlers change the array in the
handler_chain function.

2 files changed, 14 insertions, 2 deletions

diff --git a/lib/nickserver/request_handlers/email_handler.rb b/lib/nickserver/request_handlers/email_handler.rb
index 3f7515d..b163b27 100644
--- a/lib/nickserver/request_handlers/email_handler.rb
+++ b/lib/nickserver/request_handlers/email_handler.rb
@@ -8,6 +8,13 @@ module Nickserver
     class EmailHandler
 
       def call(request)
+        return unless request.email
+        handle_request(request)
+      end
+
+      protected
+
+      def handle_request(request)
         email = EmailAddress.new(request.email)
         if email.invalid?
           ErrorResponse.new("Not a valid address")
@@ -16,8 +23,6 @@ module Nickserver
         end
       end
 
-      protected
-
       def send_key(email, request)
         if local_address?(email, request)
           source = Nickserver::CouchDB::Source.new
diff --git a/lib/nickserver/request_handlers/fingerprint_handler.rb b/lib/nickserver/request_handlers/fingerprint_handler.rb
index 3202c41..3c04fcd 100644
--- a/lib/nickserver/request_handlers/fingerprint_handler.rb
+++ b/lib/nickserver/request_handlers/fingerprint_handler.rb
@@ -6,6 +6,13 @@ module Nickserver
     class FingerprintHandler
 
       def call(request)
+        return unless request.fingerprint
+        handle_request(request)
+      end
+
+      protected
+
+      def handle_request(request)
         fingerprint = request.fingerprint
         if fingerprint.length == 40 && !fingerprint[/\H/]
           source = Nickserver::Hkp::Source.new