Refactoring validation to belong to model

internal/models/note.go

@@ -19,3 +19,22 @@ type Note struct {
 	// Content is the actual text content of the note.
 	Content string `json:"content"`
 }
+
+func (n *Note) Validate() error {
+	errs := []error{}
+	if n.Title == "" {
+		errs = append(errs, &ErrEmptyNoteTitle{})
+	}
+	if n.Content == "" {
+		errs = append(errs, &ErrEmptyNoteContent{})
+	}
+	if len(errs) != 0 {
+		return &ErrNoteIncomplete{why: errs}
+	}
+	if titleLen := len(n.Title); titleLen > NoteTitleMaxLength {
+		return &ErrNoteTitleOverflow{
+			length: titleLen,
+		}
+	}
+	return nil
+}