feat(remote-control): remote control support for xtream and stalker live tv

apps/web/src/app/shared/services/remote-channel-navigation.util.ts

@@ -0,0 +1,34 @@
+export type RemoteChannelDirection = 'up' | 'down';
+
+/**
+ * Returns the adjacent item in the list for remote channel navigation.
+ * Uses wraparound when reaching the start or end of the list.
+ */
+export function getAdjacentChannelItem<T>(
+    items: T[],
+    activeId: string | number | null | undefined,
+    direction: RemoteChannelDirection,
+    getId: (item: T) => string | number | null | undefined
+): T | null {
+    if (!Array.isArray(items) || items.length === 0 || activeId == null) {
+        return null;
+    }
+
+    const activeIdAsString = String(activeId);
+    const currentIndex = items.findIndex((item) => {
+        const itemId = getId(item);
+        return itemId != null && String(itemId) === activeIdAsString;
+    });
+
+    if (currentIndex === -1) {
+        return null;
+    }
+
+    const length = items.length;
+    const nextIndex =
+        direction === 'up'
+            ? (currentIndex - 1 + length) % length
+            : (currentIndex + 1) % length;
+
+    return items[nextIndex] ?? null;
+}