React Native Code Generation

// Task: Create a toggle that animates using spring physics
// Requirements:
// - Must use useSharedValue (not Animated.Value)
// - Must use withSpring with damping/stiffness config
// - Must animate both scale and backgroundColor
// - Must handle onPress toggling state

// ❌ What most models generate (timing-based):
const opacity = useSharedValue(0);
const style = useAnimatedStyle(() => ({
  opacity: withTiming(opacity.value, { duration: 300 }),
}));

// ✅ What the eval requires (spring physics):
const progress = useSharedValue(0);
const animatedStyle = useAnimatedStyle(() => ({
  transform: [{ scale: interpolate(progress.value, [0, 1], [1, 0.95]) }],
  backgroundColor: interpolateColor(
    progress.value,
    [0, 1],
    ['#3b82f6', '#22c55e']
  ),
}));

const toggle = () => {
  progress.value = withSpring(
    progress.value === 0 ? 1 : 0,
    { damping: 15, stiffness: 150 }
  );
};

// Task: Build a chat interface with FlashList
// Requirements:
// - MUST use FlashList, not FlatList
// - Must set inverted={true} for bottom-to-top message flow
// - Must provide estimatedItemSize (required by FlashList)
// - Must implement getItemType for sent vs received messages
// - Must scroll to end on new message

import { FlashList } from '@shopify/flash-list';

<FlashList
  data={messages}
  inverted
  estimatedItemSize={72}
  renderItem={({ item }) => <MessageBubble message={item} />}
  getItemType={(item) => item.sender === 'me' ? 'sent' : 'received'}
  ref={listRef}
  onContentSizeChange={() => listRef.current?.scrollToEnd()}
/>

// Task: Prevent navigation when form has unsaved changes
// Requirements:
// - Must use beforeRemove event listener
// - Must track dirty state from form inputs
// - Must show Alert with Discard/Cancel options
// - Must remove listener when changes are saved

import { useNavigation } from '@react-navigation/native';
import { Alert } from 'react-native';

const [isDirty, setIsDirty] = useState(false);

useEffect(() => {
  if (!isDirty) return;
  
  const unsubscribe = navigation.addListener('beforeRemove', (e) => {
    e.preventDefault();
    Alert.alert(
      'Unsaved Changes',
      'You have unsaved changes. Discard them?',
      [
        { text: 'Cancel', style: 'cancel' },
        {
          text: 'Discard',
          style: 'destructive',
          onPress: () => navigation.dispatch(e.data.action),
        },
      ]
    );
  });
  
  return unsubscribe;
}, [isDirty, navigation]);