import { useState, useCallback } from 'react';
import {
  View,
  Text,
  FlatList,
  TouchableOpacity,
  ActivityIndicator,
  Image,
  RefreshControl,
  StyleSheet,
} from 'react-native';
import { useRouter } from 'expo-router';
import { Ionicons } from '@expo/vector-icons';
import { useQuery } from '@tanstack/react-query';
import { useTranslation } from 'react-i18next';
import { apiFetch } from '../../lib/api';
import { AppHeader } from '../../components/AppHeader';
import { RoomCard, type Room } from '../../components/chat/RoomCard';
import { CreateRoomSheet } from '../../components/chat/CreateRoomSheet';
import { useColors } from '../../lib/theme';

type DmConversation = {
  partnerId: string;
  partnerName: string;
  partnerAvatar: string | null;
  lastMessage: string;
  lastMessageAt: string;
  unreadCount: number;
  isOwn: boolean;
};

function formatTime(ts: string, justNowLabel: string): string {
  const diff = Date.now() - new Date(ts).getTime();
  if (diff < 60_000) return justNowLabel;
  if (diff < 3_600_000) return `${Math.floor(diff / 60_000)}m`;
  if (diff < 86_400_000) return `${Math.floor(diff / 3_600_000)}h`;
  return new Date(ts).toLocaleDateString('de-DE', { day: '2-digit', month: '2-digit' });
}

function DmItem({ conv, onPress }: { conv: DmConversation; onPress: () => void }) {
  const { t } = useTranslation();
  const colors = useColors();
  const styles = makeStyles(colors);
  const hasUnread = conv.unreadCount > 0;

  return (
    <TouchableOpacity onPress={onPress} activeOpacity={0.7}>
      <View style={styles.dmRow}>
        <View style={styles.dmAvatar}>
          {conv.partnerAvatar ? (
            <Image source={{ uri: conv.partnerAvatar }} style={styles.dmAvatarImg} />
          ) : (
            <Text style={styles.dmAvatarInitials}>
              {conv.partnerName.slice(0, 2).toUpperCase()}
            </Text>
          )}
        </View>
        <View style={styles.dmInfo}>
          <View style={styles.dmHeaderRow}>
            <Text style={styles.dmName} numberOfLines={1}>
              {conv.partnerName}
            </Text>
            <Text style={[styles.dmTime, { color: hasUnread ? '#007AFF' : colors.textMuted }]}>
              {formatTime(conv.lastMessageAt, t('chat.just_now'))}
            </Text>
          </View>
          <View style={styles.dmBottomRow}>
            <Text
              numberOfLines={1}
              style={[
                styles.dmLast,
                {
                  fontFamily: hasUnread ? 'Nunito_600SemiBold' : 'Nunito_400Regular',
                  color: hasUnread ? colors.text : colors.textMuted,
                },
              ]}
            >
              {conv.isOwn ? `${t('chat.you')} ` : ''}
              {conv.lastMessage}
            </Text>
            {hasUnread && (
              <View style={styles.unreadBadge}>
                <Text style={styles.unreadBadgeText}>
                  {conv.unreadCount > 99 ? '99+' : conv.unreadCount}
                </Text>
              </View>
            )}
          </View>
        </View>
      </View>
    </TouchableOpacity>
  );
}

export default function ChatScreen() {
  const { t } = useTranslation();
  const router = useRouter();
  const colors = useColors();
  const styles = makeStyles(colors);
  const [tab, setTab] = useState<'groups' | 'direct'>('groups');
  const [createOpen, setCreateOpen] = useState(false);

  const {
    data: rooms = [],
    isLoading: loadingRooms,
    isRefetching: refetchingRooms,
    refetch: refetchRooms,
  } = useQuery<Room[]>({
    queryKey: ['chat-rooms'],
    queryFn: () => apiFetch('/api/chat/rooms'),
    staleTime: 30_000,
  });

  const {
    data: convs = [],
    isLoading: loadingDms,
    isRefetching: refetchingDms,
    refetch: refetchDms,
  } = useQuery<DmConversation[]>({
    queryKey: ['dm-conversations'],
    queryFn: () => apiFetch('/api/chat/dm-conversations'),
    staleTime: 30_000,
    enabled: tab === 'direct',
  });

  const unreadDms = convs.reduce((s, c) => s + (c.unreadCount ?? 0), 0);

  const openRoom = useCallback(
    (roomId: string) => {
      router.push(`/room?roomId=${roomId}`);
    },
    [router],
  );

  const openDm = useCallback(
    (userId: string) => {
      router.push(`/dm?userId=${userId}`);
    },
    [router],
  );

  return (
    <View style={styles.container}>
      <AppHeader />

      {/* Header */}
      <View style={styles.headerSection}>
        <View style={styles.titleRow}>
          <Text style={styles.title}>{t('chat.title')}</Text>
          {tab === 'groups' && (
            <TouchableOpacity
              onPress={() => setCreateOpen(true)}
              activeOpacity={0.7}
              style={styles.createBtn}
            >
              <Ionicons name="add" size={20} color="#fff" />
            </TouchableOpacity>
          )}
        </View>

        {/* Tabs */}
        <View style={styles.tabs}>
          <TouchableOpacity
            onPress={() => setTab('groups')}
            activeOpacity={0.7}
            style={[styles.tab, tab === 'groups' && styles.tabActive]}
          >
            <Ionicons
              name="people"
              size={14}
              color={tab === 'groups' ? '#007AFF' : '#737373'}
            />
            <Text style={[styles.tabText, tab === 'groups' && styles.tabTextActive]}>
              {t('chat.groups')}
            </Text>
          </TouchableOpacity>
          <TouchableOpacity
            onPress={() => setTab('direct')}
            activeOpacity={0.7}
            style={[styles.tab, tab === 'direct' && styles.tabActive]}
          >
            <Ionicons
              name="chatbubbles"
              size={14}
              color={tab === 'direct' ? '#007AFF' : '#737373'}
            />
            <Text style={[styles.tabText, tab === 'direct' && styles.tabTextActive]}>
              {t('chat.direct')}
            </Text>
            {unreadDms > 0 && (
              <View style={styles.tabBadge}>
                <Text style={styles.tabBadgeText}>{unreadDms}</Text>
              </View>
            )}
          </TouchableOpacity>
        </View>
      </View>

      {tab === 'groups' ? (
        <FlatList
          data={loadingRooms ? [] : rooms}
          keyExtractor={(item) => item.id}
          refreshControl={
            <RefreshControl
              refreshing={refetchingRooms}
              onRefresh={refetchRooms}
              tintColor="#007AFF"
            />
          }
          ListEmptyComponent={
            loadingRooms ? (
              <View style={styles.emptyBox}>
                <ActivityIndicator color="#007AFF" />
              </View>
            ) : (
              <View style={styles.emptyBox}>
                <Ionicons name="people-outline" size={42} color="#d4d4d4" />
                <Text style={styles.emptyText}>{t('chat.no_rooms')}</Text>
              </View>
            )
          }
          renderItem={({ item }) => <RoomCard room={item} onPress={() => openRoom(item.id)} />}
          contentContainerStyle={{ paddingBottom: 100 }}
        />
      ) : (
        <FlatList
          data={loadingDms ? [] : convs}
          keyExtractor={(item) => item.partnerId}
          refreshControl={
            <RefreshControl
              refreshing={refetchingDms}
              onRefresh={refetchDms}
              tintColor="#007AFF"
            />
          }
          ListEmptyComponent={
            loadingDms ? (
              <View style={styles.emptyBox}>
                <ActivityIndicator color="#007AFF" />
              </View>
            ) : (
              <View style={styles.emptyBox}>
                <Ionicons name="chatbubble-ellipses-outline" size={42} color="#d4d4d4" />
                <Text style={styles.emptyText}>{t('chat.no_chats')}</Text>
              </View>
            )
          }
          renderItem={({ item }) => <DmItem conv={item} onPress={() => openDm(item.partnerId)} />}
          contentContainerStyle={{ paddingBottom: 100 }}
        />
      )}

      <CreateRoomSheet
        visible={createOpen}
        onClose={() => setCreateOpen(false)}
        onCreated={(room) => {
          refetchRooms();
          openRoom(room.id);
        }}
      />
    </View>
  );
}

function makeStyles(colors: ReturnType<typeof useColors>) {
  return StyleSheet.create({
    container: { flex: 1, backgroundColor: colors.bg },
    headerSection: {
      paddingHorizontal: 16,
      paddingTop: 14,
      paddingBottom: 10,
      backgroundColor: colors.bg,
      borderBottomWidth: StyleSheet.hairlineWidth,
      borderBottomColor: colors.border,
    },
    titleRow: {
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'space-between',
    },
    title: {
      fontSize: 22,
      fontFamily: 'Nunito_800ExtraBold',
      color: colors.text,
    },
    createBtn: {
      width: 34,
      height: 34,
      borderRadius: 17,
      backgroundColor: '#007AFF',
      alignItems: 'center',
      justifyContent: 'center',
    },
    tabs: {
      flexDirection: 'row',
      marginTop: 12,
      backgroundColor: colors.surfaceElevated,
      borderRadius: 10,
      padding: 3,
    },
    tab: {
      flex: 1,
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'center',
      paddingVertical: 7,
      borderRadius: 8,
    },
    tabActive: {
      backgroundColor: colors.surface,
      shadowColor: '#000',
      shadowOpacity: 0.05,
      shadowRadius: 2,
      shadowOffset: { width: 0, height: 1 },
    },
    tabText: {
      fontSize: 12,
      fontFamily: 'Nunito_600SemiBold',
      color: colors.textMuted,
      marginLeft: 5,
    },
    tabTextActive: {
      color: '#007AFF',
      fontFamily: 'Nunito_700Bold',
    },
    tabBadge: {
      minWidth: 16,
      height: 16,
      borderRadius: 8,
      backgroundColor: '#007AFF',
      paddingHorizontal: 4,
      alignItems: 'center',
      justifyContent: 'center',
      marginLeft: 5,
    },
    tabBadgeText: {
      fontSize: 9,
      fontFamily: 'Nunito_700Bold',
      color: '#fff',
    },
    emptyBox: {
      alignItems: 'center',
      justifyContent: 'center',
      paddingVertical: 60,
      paddingHorizontal: 32,
    },
    emptyText: {
      fontSize: 13,
      fontFamily: 'Nunito_600SemiBold',
      color: colors.textMuted,
      marginTop: 12,
    },
    dmRow: {
      flexDirection: 'row',
      alignItems: 'center',
      paddingHorizontal: 16,
      paddingVertical: 12,
      backgroundColor: colors.bg,
      borderBottomWidth: StyleSheet.hairlineWidth,
      borderBottomColor: colors.border,
      minHeight: 68,
    },
    dmAvatar: {
      width: 48,
      height: 48,
      borderRadius: 24,
      backgroundColor: colors.surfaceElevated,
      alignItems: 'center',
      justifyContent: 'center',
      overflow: 'hidden',
      marginRight: 12,
      flexShrink: 0,
    },
    dmAvatarImg: { width: 48, height: 48 },
    dmAvatarInitials: {
      fontSize: 15,
      fontFamily: 'Nunito_700Bold',
      color: colors.textMuted,
    },
    dmInfo: { flex: 1, minWidth: 0 },
    dmHeaderRow: {
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'space-between',
    },
    dmName: {
      fontSize: 15,
      fontFamily: 'Nunito_700Bold',
      color: colors.text,
      flexShrink: 1,
      marginRight: 6,
    },
    dmTime: { fontSize: 11, fontFamily: 'Nunito_500Medium' },
    dmBottomRow: {
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'space-between',
      marginTop: 2,
    },
    dmLast: { fontSize: 12, flex: 1 },
    unreadBadge: {
      minWidth: 20,
      height: 20,
      paddingHorizontal: 6,
      borderRadius: 10,
      backgroundColor: '#007AFF',
      alignItems: 'center',
      justifyContent: 'center',
      marginLeft: 8,
    },
    unreadBadgeText: {
      fontSize: 10,
      fontFamily: 'Nunito_700Bold',
      color: '#fff',
    },
  });
}