Refactor new motion form processing

- extract form parsing into helper method app.decodePostForm
- extract field checks into form.Validate

cmd/boardvoting/handlers.go

@@ -324,7 +324,7 @@ func (app *application) newMotionForm(w http.ResponseWriter, r *http.Request) {
 	app.render(w, http.StatusOK, "create_motion.html", data)
 }
 
-func (app *application) newMotionSubmit(w http.ResponseWriter, r *http.Request) {
+func (form *NewMotionForm) Validate() {
 	const (
 		minimumTitleLength   = 3
 		maximumTitleLength   = 200
@@ -335,28 +335,8 @@ func (app *application) newMotionSubmit(w http.ResponseWriter, r *http.Request)
 		oneWeek    = 7
 		twoWeeks   = 14
 		threeWeeks = 28
-
-		hoursInDay = 24
 	)
 
-	err := r.ParseForm()
-	if err != nil {
-		app.clientError(w, http.StatusBadRequest)
-
-		return
-	}
-
-	var form NewMotionForm
-
-	err = app.formDecoder.Decode(&form, r.PostForm)
-	if err != nil {
-		app.errorLog.Printf("form decoding failed: %v", err)
-
-		app.clientError(w, http.StatusBadRequest)
-
-		return
-	}
-
 	form.CheckField(
 		validator.NotBlank(form.Title),
 		"title",
@@ -391,6 +371,21 @@ func (app *application) newMotionSubmit(w http.ResponseWriter, r *http.Request)
 	form.CheckField(validator.PermittedInt(
 		form.Due, threeDays, oneWeek, twoWeeks, threeWeeks), "due", "invalid duration choice",
 	)
+}
+
+func (app *application) newMotionSubmit(w http.ResponseWriter, r *http.Request) {
+	const hoursInDay = 24
+
+	var form NewMotionForm
+
+	err := app.decodePostForm(r, &form)
+	if err != nil {
+		app.clientError(w, http.StatusBadRequest)
+
+		return
+	}
+
+	form.Validate()
 
 	if !form.Valid() {
 		form.User = &models.User{}
@@ -441,7 +436,7 @@ func (app *application) newMotionSubmit(w http.ResponseWriter, r *http.Request)
 
 	// TODO: add flash message for new motion
 
-	http.Redirect(w, r, fmt.Sprintf("/motions/%s", decision.Tag), http.StatusFound)
+	http.Redirect(w, r, fmt.Sprintf("/motions/%s", decision.Tag), http.StatusSeeOther)
 }
 
 func (app *application) editMotionForm(_ http.ResponseWriter, _ *http.Request) {

cmd/boardvoting/helpers.go

@@ -18,9 +18,12 @@ limitations under the License.
 package main
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"runtime/debug"
+
+	"github.com/go-playground/form/v4"
 )
 
 func (app *application) serverError(w http.ResponseWriter, err error) {
@@ -38,3 +41,23 @@ func (app *application) clientError(w http.ResponseWriter, status int) {
 func (app *application) notFound(w http.ResponseWriter) {
 	app.clientError(w, http.StatusNotFound)
 }
+
+func (app *application) decodePostForm(r *http.Request, dst any) error {
+	err := r.ParseForm()
+	if err != nil {
+		return fmt.Errorf("could not parse HTML form: %w", err)
+	}
+
+	err = app.formDecoder.Decode(dst, r.PostForm)
+	if err != nil {
+		var invalidDecoderError *form.InvalidDecoderError
+
+		if errors.As(err, &invalidDecoderError) {
+			panic(err)
+		}
+
+		return fmt.Errorf("could not decode form: %w", err)
+	}
+
+	return nil
+}