feat: add foreach util function

Signed-off-by: nscuro <[email protected]>

util.go

@@ -1,25 +1,45 @@
 package dtrack
 
+import "fmt"
+
 // FetchAll is a convenience function to retrieve all items of a paginated API resource.
-func FetchAll[T any](f func(po PageOptions) (Page[T], error)) (items []T, err error) {
+func FetchAll[T any](pageFetchFunc func(po PageOptions) (Page[T], error)) (items []T, err error) {
+	err = ForEach(pageFetchFunc, func(item T) error {
+		items = append(items, item)
+		return nil
+	})
+
+	return
+}
+
+// ForEach is a convenience function to perform an action on every item of a paginated API resource.
+func ForEach[T any](pageFetchFunc func(po PageOptions) (Page[T], error), handlerFunc func(item T) error) (err error) {
 	const pageSize = 50
 
 	var (
 		page       Page[T]
 		pageNumber = 1
+		itemsSeen  = 0
 	)
 
 	for {
-		page, err = f(PageOptions{
+		page, err = pageFetchFunc(PageOptions{
 			PageNumber: pageNumber,
 			PageSize:   pageSize,
 		})
 		if err != nil {
 			break
 		}
 
-		items = append(items, page.Items...)
-		if len(page.Items) == 0 || len(items) >= page.TotalCount {
+		for i := range page.Items {
+			err = handlerFunc(page.Items[i])
+			if err != nil {
+				return fmt.Errorf("failed to handle item %d on page %d: %w", i+1, pageNumber, err)
+			}
+		}
+
+		itemsSeen += page.TotalCount
+		if len(page.Items) == 0 || itemsSeen >= page.TotalCount {
 			break
 		}