refactor: optimize keyboard navigation logic with modular arithmetic

Author: aojunhao123

src/index.tsx

@@ -201,26 +201,28 @@ const Segmented = React.forwardRef<HTMLDivElement, SegmentedProps>(
     };
 
     // ======================= Keyboard ========================
-    const handleKeyDown = (event: React.KeyboardEvent) => {
+    const onOffset = (offset: number) => {
       const total = segmentedOptions.length;
-      let nextIndex = currentIndex;
+      const nextIndex = (currentIndex + offset + total) % total;
+
+      const nextOption = segmentedOptions[nextIndex];
+      if (nextOption) {
+        setRawValue(nextOption.value);
+        onChange?.(nextOption.value);
+      }
+    };
 
+    const handleKeyDown = (event: React.KeyboardEvent) => {
       switch (event.key) {
         case 'ArrowLeft':
         case 'ArrowUp':
-          nextIndex = currentIndex === 0 ? total - 1 : currentIndex - 1;
+          onOffset(-1);
           break;
         case 'ArrowRight':
         case 'ArrowDown':
-          nextIndex = currentIndex === total - 1 ? 0 : currentIndex + 1;
+          onOffset(1);
           break;
       }
-
-      const nextOption = segmentedOptions[nextIndex];
-      if (nextOption) {
-        setRawValue(nextOption.value);
-        onChange?.(nextOption.value);
-      }
     };
 
     return (