import { router } from 'expo-router';
import { useEffect, useState } from 'react';
import { Pressable, RefreshControl, ScrollView, StyleSheet, Text, View } from 'react-native';
import Animated, { FadeInDown, LinearTransition } from 'react-native-reanimated';
import { SafeAreaView } from 'react-native-safe-area-context';
import useSWR from 'swr';
import { sortFeed, type ConnectionDTO, type FeedItemDTO, type FollowListDTO, type ProfileDTO } from '@musicshare/shared';
import { AmbientBackground } from '@/components/AmbientBackground';
import { Avatar } from '@/components/Avatar';
import { NowPlayingCard } from '@/components/NowPlayingCard';
import { RelinkReminder } from '@/components/RelinkReminder';
import { SharingControls } from '@/components/SharingControls';
import { Body, Button, Card, Title } from '@/components/ui';
import { api } from '@/lib/api';
import { showError } from '@/lib/errors';
import { appleMusicAvailable } from '@/lib/appleMusic';
import { useReader } from '@/lib/nowPlayingReader';
import { shouldOfferSetup } from '@/lib/setup';
import { useRealtime } from '@/lib/useRealtime';
import { useSession } from '@/lib/session';
import { colors, space } from '@/lib/theme';

export default function FeedScreen() {
  const { me } = useSession();
  const { data: feed, mutate, isLoading } = useSWR<FeedItemDTO[]>('/feed');
  // Your own profile, for the "You" card. Loading it also marks you as watched, so your updates arrive quickly.
  const { data: mine, mutate: mutateMine } = useSWR<ProfileDTO>(me ? `/users/${me.username}` : null);
  // Everyone you follow; the feed only has the ones who've played something.
  const { data: following, mutate: mutateFollowing } = useSWR<FollowListDTO>(me ? `/users/${me.username}/following` : null);
  const inFeed = new Set(feed?.map((n) => n.user.id));
  const quiet = following?.users.filter((u) => !inFeed.has(u.id)) ?? [];
  const [refreshing, setRefreshing] = useState(false);

  const reader = useReader();
  const { data: connections } = useSWR<ConnectionDTO[]>(appleMusicAvailable ? '/connections' : null);
  const offerAppleMusic = appleMusicAvailable && connections !== undefined && connections.length === 0;

  // First run on Android: open the one-tap setup once (deferred so navigation has mounted).
  useEffect(() => {
    const timer = setTimeout(() => {
      shouldOfferSetup().then((offer) => offer && router.push('/share-setup'));
    }, 400);
    return () => clearTimeout(timer);
  }, []);

  useRealtime(true, (msg) => {
    if (msg.type !== 'now_playing') return;
    if (msg.data.user.id === me?.id) {
      if (mine) mutateMine({ ...mine, nowPlaying: msg.data }, { revalidate: false });
      return;
    }
    mutate(
      (current = []) => {
        const existing = current.find((n) => n.user.id === msg.data.user.id);
        return sortFeed([{ ...msg.data, pinnedAt: existing?.pinnedAt ?? null }, ...current.filter((n) => n !== existing)]);
      },
      { revalidate: false },
    );
  });

  const togglePin = async (item: FeedItemDTO) => {
    const pinnedAt = item.pinnedAt ? null : new Date().toISOString();
    const previous = feed;
    mutate(sortFeed((feed ?? []).map((n) => (n.user.id === item.user.id ? { ...n, pinnedAt } : n))), { revalidate: false });
    try {
      await (pinnedAt ? api.pin(item.user.username) : api.unpin(item.user.username));
    } catch (err) {
      mutate(previous, { revalidate: false });
      showError(err, "Couldn't pin");
    }
  };

  const refresh = async () => {
    setRefreshing(true);
    await Promise.all([mutate(), mutateMine(), mutateFollowing()]).catch(() => {});
    setRefreshing(false);
  };

  return (
    <SafeAreaView style={styles.safe} edges={['top']}>
      <AmbientBackground />
      {/* Cards rise in on load and glide to new positions when someone pins or starts playing. */}
      <Animated.FlatList
        itemLayoutAnimation={LinearTransition.springify().damping(18)}
        data={feed ?? []}
        keyExtractor={(item) => item.user.id}
        contentContainerStyle={styles.list}
        refreshControl={<RefreshControl refreshing={refreshing} onRefresh={refresh} tintColor={colors.muted} />}
        ListHeaderComponent={
          <View style={styles.header}>
            <SharingControls compact />
            <RelinkReminder />
            {offerAppleMusic && (
              <Card>
                <Body>Connect Apple Music so friends see what you play. One tap.</Body>
                <Button small variant="primary" title="Connect" onPress={() => router.push('/share-setup')} style={{ alignSelf: 'flex-start' }} />
              </Card>
            )}
            {reader.available && !reader.granted && (
              <Card>
                <Body>Share what you’re playing in Spotify, YouTube Music and other apps. One tap, no accounts.</Body>
                <Button small variant="primary" title="Turn on" onPress={() => router.push('/share-setup')} style={{ alignSelf: 'flex-start' }} />
              </Card>
            )}
            {mine?.nowPlaying && (
              <View style={{ gap: space.sm }}>
                <Text style={styles.sectionLabel}>YOU</Text>
                <NowPlayingCard np={mine.nowPlaying} preferred={me?.preferredService} showUser={false} />
              </View>
            )}
            <Title>Friends listening</Title>
            {!me?.preferredService && (
              <Card>
                <Body>Pick your streaming service so songs open in the right app.</Body>
                <Button small title="Choose service" onPress={() => router.push('/settings')} style={{ alignSelf: 'flex-start' }} />
              </Card>
            )}
          </View>
        }
        ListEmptyComponent={
          isLoading ? null : (
            <Card>
              <Body muted>
                {following?.users.length
                  ? 'Nobody you follow has played anything yet. Their music will show up here live.'
                  : 'Nothing yet. Follow some friends and their music will show up here live.'}
              </Body>
              <Button small variant="primary" title="Find friends" onPress={() => router.push('/search')} style={{ alignSelf: 'flex-start' }} />
            </Card>
          )
        }
        ListFooterComponent={
          quiet.length > 0 ? (
            <View style={{ gap: space.sm, marginTop: space.md }}>
              <Text style={styles.sectionLabel}>FOLLOWING · NOTHING PLAYED YET</Text>
              <ScrollView horizontal showsHorizontalScrollIndicator={false} contentContainerStyle={styles.quiet}>
                {quiet.map((u) => (
                  <Pressable key={u.id} onPress={() => router.push(`/u/${u.username}`)} style={styles.quietPerson} accessibilityLabel={u.displayName ?? u.username}>
                    <Avatar user={u} size={52} />
                    <Text style={styles.quietName} numberOfLines={1}>
                      {u.displayName ?? u.username}
                    </Text>
                  </Pressable>
                ))}
                {following?.nextCursor && me && (
                  <Pressable onPress={() => router.push(`/u/${me.username}/following`)} style={[styles.quietPerson, { justifyContent: 'center' }]}>
                    <Text style={[styles.quietName, { color: colors.muted }]}>See all</Text>
                  </Pressable>
                )}
              </ScrollView>
            </View>
          ) : null
        }
        renderItem={({ item, index }) => (
          <Animated.View entering={FadeInDown.delay(Math.min(index, 8) * 60).springify().damping(16)}>
            <NowPlayingCard
              np={item}
              preferred={me?.preferredService}
              pinned={Boolean(item.pinnedAt)}
              onTogglePin={() => togglePin(item)}
            />
          </Animated.View>
        )}
      />
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  safe: { flex: 1, backgroundColor: colors.bg },
  list: { padding: space.lg, gap: space.md, paddingBottom: space.xl * 3 },
  header: { gap: space.md, marginBottom: space.xs },
  sectionLabel: { color: colors.muted, fontSize: 12, fontWeight: '700', letterSpacing: 0.8 },
  quiet: { gap: space.lg, paddingVertical: space.xs },
  quietPerson: { width: 64, alignItems: 'center', gap: 4 },
  quietName: { color: colors.text, fontSize: 12, textAlign: 'center' },
});