init commit

1 files changed, 25 insertions, 0 deletions

diff --git a/shared/components/src/utils/getUpdatedFocusedIndex.ts b/shared/components/src/utils/getUpdatedFocusedIndex.ts
new file mode 100644
index 0000000..ca2c765
--- /dev/null
+++ b/shared/components/src/utils/getUpdatedFocusedIndex.ts
@@ -0,0 +1,25 @@
+export function getUpdatedFocusedIndex(
+    incrementAmount: number,
+    currentFocusedIndex: number | null,
+    numberOfItems: number,
+): number {
+    const potentialFocusedIndex = incrementAmount + currentFocusedIndex;
+
+    if (incrementAmount > 0) {
+        if (currentFocusedIndex === null) {
+            return 0;
+        } else {
+            return potentialFocusedIndex >= numberOfItems
+                ? 0
+                : potentialFocusedIndex;
+        }
+    } else {
+        if (currentFocusedIndex === null) {
+            return numberOfItems - 1;
+        } else {
+            return potentialFocusedIndex < 0
+                ? numberOfItems - 1
+                : potentialFocusedIndex;
+        }
+    }
+}