refactor(casting): extract useCastDismissGesture hook

hooks/useCastDismissGesture.ts

@@ -0,0 +1,69 @@
+import type { Router } from "expo-router";
+import { useCallback } from "react";
+import { Gesture } from "react-native-gesture-handler";
+import {
+  runOnJS,
+  useAnimatedStyle,
+  useSharedValue,
+  withSpring,
+} from "react-native-reanimated";
+
+interface UseCastDismissGestureParams {
+  router: Router;
+}
+
+/**
+ * Swipe-down-to-dismiss gesture cluster for the casting player modal.
+ * Owns the `translateY`/`context` shared values, the pan gesture, the animated
+ * style, and the `dismissModal` callback (also invoked by the header button).
+ */
+export function useCastDismissGesture({ router }: UseCastDismissGestureParams) {
+  // Swipe down to dismiss gesture
+  const translateY = useSharedValue(0);
+  const context = useSharedValue({ y: 0 });
+
+  const dismissModal = useCallback(() => {
+    // Navigate immediately without animation to prevent crashes
+    if (router.canGoBack()) {
+      router.back();
+    } else {
+      router.replace("/(auth)/(tabs)/(home)/");
+    }
+  }, [router]);
+
+  const panGesture = Gesture.Pan()
+    .onStart(() => {
+      context.value = { y: translateY.value };
+    })
+    .onUpdate((event) => {
+      // Only allow downward swipes from top of screen
+      if (event.translationY > 0) {
+        translateY.value = context.value.y + event.translationY;
+      }
+    })
+    .onEnd((event) => {
+      // Dismiss if swiped down more than 150px or fast swipe
+      if (event.translationY > 150 || event.velocityY > 600) {
+        // Animate down and dismiss
+        translateY.value = withSpring(
+          1000,
+          {
+            damping: 20,
+            stiffness: 90,
+          },
+          () => {
+            runOnJS(dismissModal)();
+          },
+        );
+      } else {
+        // Spring back to position
+        translateY.value = withSpring(0);
+      }
+    });
+
+  const animatedStyle = useAnimatedStyle(() => ({
+    transform: [{ translateY: translateY.value }],
+  }));
+
+  return { panGesture, animatedStyle, dismissModal };
+}