import { useCallback, useState } from 'react';
import {
  View,
  Text,
  ScrollView,
  FlatList,
  Pressable,
  RefreshControl,
  ActivityIndicator,
} from 'react-native';
import { Ionicons } from '@expo/vector-icons';
import { useQuery, useQueryClient } from '@tanstack/react-query';
import { useTranslation } from 'react-i18next';
import { apiFetch } from '../../lib/api';
import { AppHeader } from '../../components/AppHeader';
import { ComposeCard } from '../../components/ComposeCard';
import { PostCard } from '../../components/PostCard';
import { PostCardSkeleton } from '../../components/PostCardSkeleton';
import { PostCommentsSheet } from '../../components/PostCommentsSheet';
import { useCommunityStore, type CommunityCategory, type CommunityPost } from '../../stores/community';
import { useCommunityRealtime } from '../../hooks/useCommunityRealtime';
import { colors } from '../../lib/theme';

type FilterChip = {
  value: CommunityCategory;
  label: string;
  icon: React.ComponentProps<typeof Ionicons>['name'];
};

export default function HomeScreen() {
  const { t } = useTranslation();
  const queryClient = useQueryClient();
  // Granular selectors: subscribing to the whole store (incl. optimisticLikes)
  // would re-render the screen — and thus the FlatList — on every like.
  const activeCategory = useCommunityStore((s) => s.activeCategory);
  const setCategory = useCommunityStore((s) => s.setCategory);

  const FILTERS: FilterChip[] = [
    { value: 'all', label: t('community.cat_all'), icon: 'grid-outline' },
    { value: 'games', label: t('community.cat_games'), icon: 'trophy-outline' },
    { value: 'domain_vote', label: t('community.cat_domain'), icon: 'shield-outline' },
    { value: 'lyra', label: t('community.cat_lyra'), icon: 'sparkles-outline' },
    { value: 'rebreak', label: t('community.cat_rebreak'), icon: 'megaphone-outline' },
  ];
  const [filterOpen, setFilterOpen] = useState(false);
  const [activeCommentsPostId, setActiveCommentsPostId] = useState<string | null>(null);

  const { data: posts = [], isLoading, isRefetching, refetch } = useQuery<CommunityPost[]>({
    queryKey: ['community-posts', activeCategory],
    queryFn: () => apiFetch(`/api/community/posts?category=${activeCategory}&limit=30`),
    staleTime: 60_000,
  });

  // Realtime: live updates für Posts (likes/comments/neue Posts/domain-vote-Status)
  useCommunityRealtime(true);

  const toggleFilter = (value: CommunityCategory) => {
    const next = activeCategory === value ? 'all' : value;
    setCategory(next);
    setFilterOpen(false);
  };

  // Stable callbacks — passed to memoized PostCards. Inline arrows would
  // bust React.memo on every parent render (which also happens on every
  // realtime patch since the posts array gets a new reference).
  const openComments = useCallback((postId: string) => {
    setActiveCommentsPostId(postId);
  }, []);

  const closeComments = useCallback(() => setActiveCommentsPostId(null), []);

  const keyExtractor = useCallback((item: CommunityPost) => item.id, []);

  const renderItem = useCallback(
    ({ item }: { item: CommunityPost }) => (
      <PostCard post={item} onCommentPress={openComments} />
    ),
    [openComments],
  );

  return (
    <View className="flex-1 bg-neutral-50">
      <AppHeader />

      <FlatList
        data={isLoading ? [] : posts}
        keyExtractor={keyExtractor}
        contentContainerStyle={{ paddingHorizontal: 16, paddingTop: 12, paddingBottom: 32 }}
        showsVerticalScrollIndicator={false}
        // Performance tuning — measured on Galaxy A50 (older mid-range):
        // VirtualizedList warned with dt=2.26s for ~7k content. These props
        // shrink the per-batch render cost and reclaim off-screen views.
        removeClippedSubviews
        initialNumToRender={5}
        maxToRenderPerBatch={5}
        windowSize={7}
        updateCellsBatchingPeriod={50}
        refreshControl={
          <RefreshControl
            refreshing={isRefetching}
            onRefresh={refetch}
            tintColor={colors.brandOrange}
          />
        }
        ListHeaderComponent={
          <View>
            <ComposeCard onPosted={() => refetch()} />

            {/* Filter toggle */}
            <View className="mb-3">
              <Pressable
                onPress={() => setFilterOpen((o) => !o)}
                className="flex-row items-center gap-1.5 self-start"
                style={({ pressed }) => ({ opacity: pressed ? 0.6 : 1 })}
              >
                <Ionicons
                  name={filterOpen ? 'close-outline' : 'options-outline'}
                  size={18}
                  color={activeCategory !== 'all' ? colors.brandOrange : '#737373'}
                />
                {activeCategory !== 'all' && (
                  <Text className="text-xs text-rebreak-500" style={{ fontFamily: 'Nunito_600SemiBold' }}>
                    {FILTERS.find((f) => f.value === activeCategory)?.label}
                  </Text>
                )}
              </Pressable>

              {filterOpen && (
                <ScrollView
                  horizontal
                  showsHorizontalScrollIndicator={false}
                  className="mt-2"
                  contentContainerStyle={{ gap: 8, paddingBottom: 4 }}
                >
                  {FILTERS.map((f) => {
                    const active = activeCategory === f.value;
                    return (
                      <Pressable
                        key={f.value}
                        onPress={() => toggleFilter(f.value)}
                        className={`flex-row items-center gap-1.5 h-8 px-3 rounded-full border ${
                          active
                            ? 'bg-rebreak-500 border-rebreak-500'
                            : 'bg-white border-neutral-200'
                        }`}
                        style={({ pressed }) => ({ opacity: pressed ? 0.7 : 1 })}
                      >
                        <Ionicons
                          name={f.icon}
                          size={13}
                          color={active ? '#fff' : '#737373'}
                        />
                        <Text
                          className={`text-xs ${
                            active ? 'text-white' : 'text-neutral-500'
                          }`}
                          style={{ fontFamily: 'Nunito_600SemiBold' }}
                        >
                          {f.label}
                        </Text>
                      </Pressable>
                    );
                  })}
                </ScrollView>
              )}
            </View>

            {/* Skeleton */}
            {isLoading && (
              <View>
                <PostCardSkeleton />
                <PostCardSkeleton />
                <PostCardSkeleton />
              </View>
            )}
          </View>
        }
        ListEmptyComponent={
          isLoading ? null : (
            <View className="items-center py-16">
              <Ionicons name="chatbubbles-outline" size={40} color="#d4d4d4" />
              <Text className="text-sm text-neutral-400 mt-3 text-center" style={{ fontFamily: 'Nunito_400Regular' }}>
                {t('community.no_posts')}
              </Text>
            </View>
          )
        }
        renderItem={renderItem}
      />

      <PostCommentsSheet
        postId={activeCommentsPostId}
        visible={activeCommentsPostId !== null}
        onClose={closeComments}
      />
    </View>
  );
}