actualize items list in db

internal/entity/iter.go

@@ -1,18 +1,49 @@
 package entity
 
-func IterWithErr[T any](t []T, err error) iterWithErr[T] {
-	return iterWithErr[T]{
+func IterIntoMap[K comparable, V any](v []V, err error) iterIntoMap[K, V] {
+	bi := IterWithErr(v, err)
+
+	return iterIntoMap[K, V]{
+		baseIter: bi,
+	}
+}
+
+type iterIntoMap[K comparable, V any] struct {
+	baseIter[V]
+}
+
+func (i iterIntoMap[K, V]) Map(f func(V) (K, error)) (map[K]V, error) {
+	if i.err != nil {
+		return nil, i.err
+	}
+
+	out := make(map[K]V, len(i.items))
+	for _, item := range i.items {
+		var key K
+		key, i.err = f(item)
+		if i.err != nil {
+			return nil, i.err
+		}
+
+		out[key] = item
+	}
+
+	return out, nil
+}
+
+func IterWithErr[T any](t []T, err error) baseIter[T] {
+	return baseIter[T]{
 		items: t,
 		err:   err,
 	}
 }
 
-type iterWithErr[T any] struct {
+type baseIter[T any] struct {
 	items []T
 	err   error
 }
 
-func (iter iterWithErr[T]) Do(f func(T) error) error {
+func (iter baseIter[T]) Do(f func(T) error) error {
 	if iter.err != nil {
 		return iter.err
 	}