diff --git a/service/api/helpers/get-limits.go b/service/api/helpers/get-limits.go
index 4e76960..3c469f1 100644
--- a/service/api/helpers/get-limits.go
+++ b/service/api/helpers/get-limits.go
@@ -6,7 +6,7 @@ import (
 )
 
 const (
-	DEFAULT_LIMIT  = 15 // don't know if should be moved to config
+	DEFAULT_LIMIT  = 15
 	DEFAULT_OFFSET = 0
 )
 
diff --git a/service/api/helpers/regex-helpers.go b/service/api/helpers/regex-helpers.go
new file mode 100644
index 0000000..b3684a7
--- /dev/null
+++ b/service/api/helpers/regex-helpers.go
@@ -0,0 +1,33 @@
+package helpers
+
+import (
+	"net/http"
+	"regexp"
+
+	"github.com/sirupsen/logrus"
+)
+
+func MatchRegexOrBadRequest(str string, regex string, error_description string, w http.ResponseWriter, l logrus.FieldLogger) bool {
+
+	stat, err := regexp.Match(regex, []byte(str))
+
+	if err != nil {
+		SendInternalError(err, "Error while matching username regex", w, l)
+		return false
+	}
+
+	if !stat {
+		// string didn't match the regex, so it's invalid, let's send a bad request error
+		SendBadRequest(w, error_description, l)
+		return false
+	}
+	// string matched the regex, so it's valid
+	return true
+}
+
+func MatchUsernameOrBadRequest(username string, w http.ResponseWriter, l logrus.FieldLogger) bool {
+	return MatchRegexOrBadRequest(username,
+		`^[a-zA-Z0-9_]{3,16}$`, "Username must be between 3 and 16 characters long and can only contain letters, numbers and underscores",
+		w,
+		l)
+}
diff --git a/service/api/post-session.go b/service/api/post-session.go
index fabff85..faeb5ef 100644
--- a/service/api/post-session.go
+++ b/service/api/post-session.go
@@ -3,7 +3,6 @@ package api
 import (
 	"encoding/json"
 	"net/http"
-	"regexp"
 
 	"github.com/julienschmidt/httprouter"
 	"github.com/notherealmarco/WASAPhoto/service/api/helpers"
@@ -26,33 +25,36 @@ func (rt *_router) PostSession(w http.ResponseWriter, r *http.Request, ps httpro
 	var request _reqbody
 	err := json.NewDecoder(r.Body).Decode(&request)
 
-	var uid string
-	if err == nil { // test if user exists
-		uid, err = rt.db.GetUserID(request.Name)
+	if err != nil {
+		helpers.SendBadRequestError(err, "Bad request body", w, rt.baseLogger)
+		return
 	}
 
-	if db_errors.EmptySet(err) { // user does not exist
+	// test if user exists
+	var uid string
+	uid, err = rt.db.GetUserID(request.Name)
 
-		// before creating the user, check if the name is valid
-		stat, regex_err := regexp.Match(`^[a-zA-Z0-9_]{3,16}$`, []byte(request.Name))
-		if regex_err != nil {
-			helpers.SendInternalError(err, "Error while matching username regex", w, rt.baseLogger)
-			return
-		}
-		if !stat {
-			// username didn't match the regex, so it's invalid, let's send a bad request error
-			helpers.SendBadRequest(w, "Username must be between 3 and 16 characters long and can only contain letters, numbers and underscores", rt.baseLogger)
+	// check if the database returned an empty set error, if so, create the new user
+	if db_errors.EmptySet(err) {
+
+		// before creating the user, check if the name is valid, otherwise send a bad request error
+		if !helpers.MatchUsernameOrBadRequest(request.Name, w, rt.baseLogger) {
 			return
 		}
 
 		uid, err = rt.db.CreateUser(request.Name)
 	}
-	if err != nil { // handle any other error
-		helpers.SendBadRequestError(err, "Bad request body", w, rt.baseLogger)
+
+	// handle database errors
+	if err != nil {
+		helpers.SendInternalError(err, "Database error", w, rt.baseLogger)
 		return
 	}
 
+	// set the response header
 	w.Header().Set("content-type", "application/json")
+
+	// encode the response body
 	err = json.NewEncoder(w).Encode(_respbody{UID: uid})
 
 	if err != nil {
diff --git a/service/api/put-updateusername.go b/service/api/put-updateusername.go
index 4e8fc19..5415a5d 100644
--- a/service/api/put-updateusername.go
+++ b/service/api/put-updateusername.go
@@ -2,7 +2,6 @@ package api
 
 import (
 	"net/http"
-	"regexp"
 
 	"github.com/julienschmidt/httprouter"
 	"github.com/notherealmarco/WASAPhoto/service/api/authorization"
@@ -15,23 +14,20 @@ import (
 func (rt *_router) UpdateUsername(w http.ResponseWriter, r *http.Request, ps httprouter.Params, ctx reqcontext.RequestContext) {
 
 	uid := ps.ByName("user_id")
+
+	// check if the user is changing his own username
 	if !authorization.SendAuthorizationError(ctx.Auth.UserAuthorized, uid, rt.db, w, rt.baseLogger, http.StatusNotFound) {
 		return
 	}
+
+	// decode request body
 	var req structures.UserDetails
 	if !helpers.DecodeJsonOrBadRequest(r.Body, w, &req, rt.baseLogger) {
 		return
 	}
 
-	stat, err := regexp.Match(`^[a-zA-Z0-9_]{3,16}$`, []byte(req.Name))
-
-	if err != nil {
-		helpers.SendInternalError(err, "Error while matching username regex", w, rt.baseLogger)
-		return
-	}
-
-	if !stat { // todo: sta regex non me piace
-		helpers.SendBadRequest(w, "Username must be between 3 and 16 characters long and can only contain letters, numbers and underscores", rt.baseLogger)
+	// check if the username is valid, and if it's not, send a bad request error
+	if !helpers.MatchUsernameOrBadRequest(req.Name, w, rt.baseLogger) {
 		return
 	}