Topic and callback should be absolute urls

cmd/hubserver/handler.go

@@ -154,16 +154,23 @@ func (handler *subscriptionHandler) handleSubscription(w http.ResponseWriter, r
 
 	callbackURL, err := url.Parse(callback)
 	if callback == "" || err != nil {
-		http.Error(w, "Can not parse callback url", 400)
-		log.Printf("Can not parse callback url: %s\n", callback)
+		http.Error(w, "cannot parse callback url", 400)
+		log.Printf("cannot parse callback url: %s", callback)
 		return err
 	}
+	if !callbackURL.IsAbs() {
+		http.Error(w, "callback url is not absolute", 400)
+		return fmt.Errorf("callback url is not absolute: %s", callback)
+	}
 
 	topicURL, err := url.Parse(topic)
 	if topic == "" || err != nil {
-		http.Error(w, "Can't parse topic url", 400)
-		log.Printf("Can't parse topic url: %s\n", topic)
-		return err
+		http.Error(w, "cannot parse topic url", 400)
+		return fmt.Errorf("cannot parse topic url: %s\n", topic)
+	}
+	if !topicURL.IsAbs() {
+		http.Error(w, "topic url is not absolute", 400)
+		return fmt.Errorf("topic url is not absolute: %s", topic)
 	}
 
 	log.Println("subscribe: sending 202 header request accepted")

db/01_tables.sql

@@ -1,4 +1,4 @@
-create table "subscribers"
+CREATE TABLE IF NOT EXISTS "subscribers"
 (
   id            int GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
   topic         varchar(255) not null,

db/02_unique.sql

@@ -0,0 +1 @@
+CREATE UNIQUE INDEX IF NOT EXISTS "subscribers_topic_callback" ON "subscribers" ("topic", "callback");