feat: cleaner parsing functions

pkg/iterator/iterator.go

@@ -48,6 +48,12 @@ func (i Iterator[T]) MustGet() T {
 	return i.items[i.index]
 }
 
+func (i *Iterator[T]) Forward() {
+	if !i.Done() {
+		i.index++
+	}
+}
+
 // Create a new iterator, over a set of items.
 func (i *Iterator[T]) Next() (T, error) {
 	item, err := i.Get()
@@ -67,3 +73,14 @@ func (i *Iterator[T]) Back() {
 func (i Iterator[T]) Done() bool {
 	return i.index == len(i.items)
 }
+
+func Do[T any, U any](i *Iterator[T], fn func(i *Iterator[T]) (U, error)) (U, error) {
+	i2 := i.Copy()
+
+	out, err := fn(i2)
+	if err == nil {
+		i.Sync(i2)
+	}
+
+	return out, err
+}