import React, { useMemo, useState } from 'react';
import { FlatList, RefreshControl, ScrollView, StyleSheet, Text, View } from 'react-native';
import { useRouter } from 'expo-router';
import { useQuery } from '@tanstack/react-query';
import { api, DocCategory } from '@/api';
import { useT } from '@/i18n';
import { AppBar } from '@/components/AppBar';
import { Chip, EmptyState, Loading } from '@/components/ui';
import { DocumentRow } from '@/components/domain';
import { DocWithProperty, fetchAllDocuments } from '@/lib/allDocuments';
import { daysUntil } from '@/lib/format';
import { colors, fontSize, spacing } from '@/theme';

type Filter = 'all' | 'expiring' | 'expired';

export default function ExpiringScreen() {
  const router = useRouter();
  const t = useT();
  const [filter, setFilter] = useState<Filter>('all');

  const docsQuery = useQuery({ queryKey: ['all-documents'], queryFn: fetchAllDocuments });
  const catsQuery = useQuery({ queryKey: ['categories'], queryFn: () => api.reference.categories() });
  const catName = (slug: string) =>
    (catsQuery.data as DocCategory[] | undefined)?.find((c) => c.slug === slug)?.name ?? slug;

  // Only documents that actually need attention, soonest deadline first.
  const attention = useMemo(() => {
    const docs: DocWithProperty[] = docsQuery.data ?? [];
    return docs
      .filter((d) => d.expiryStatus === 'expiring' || d.expiryStatus === 'expired')
      .sort((a, b) => (daysUntil(a.expiryDate) ?? 0) - (daysUntil(b.expiryDate) ?? 0));
  }, [docsQuery.data]);

  const counts = useMemo(
    () => ({
      all: attention.length,
      expiring: attention.filter((d) => d.expiryStatus === 'expiring').length,
      expired: attention.filter((d) => d.expiryStatus === 'expired').length,
    }),
    [attention],
  );

  const visible = filter === 'all' ? attention : attention.filter((d) => d.expiryStatus === filter);

  return (
    <View style={{ flex: 1, backgroundColor: colors.bgApp }}>
      <AppBar
        title={t('expiring.title')}
        subtitle={docsQuery.data ? t('expiring.subtitle', { count: counts.all }) : undefined}
        large
      />

      <ScrollView
        horizontal
        showsHorizontalScrollIndicator={false}
        contentContainerStyle={styles.chips}
        style={{ flexGrow: 0 }}
      >
        <Chip label={t('common.all')} count={counts.all} active={filter === 'all'} onPress={() => setFilter('all')} />
        <Chip
          label={t('documents.filterExpiring')}
          count={counts.expiring}
          active={filter === 'expiring'}
          onPress={() => setFilter('expiring')}
        />
        <Chip
          label={t('documents.filterExpired')}
          count={counts.expired}
          active={filter === 'expired'}
          onPress={() => setFilter('expired')}
        />
      </ScrollView>

      {docsQuery.isLoading ? (
        <Loading />
      ) : (
        <FlatList
          data={visible}
          keyExtractor={(d) => String(d.id)}
          contentContainerStyle={styles.list}
          refreshControl={
            <RefreshControl
              refreshing={docsQuery.isRefetching}
              onRefresh={() => docsQuery.refetch()}
              tintColor={colors.teal600}
            />
          }
          renderItem={({ item }) => (
            <View style={{ marginBottom: spacing[3] }}>
              <DocumentRow
                document={item}
                subtitle={`${item.propertyName} · ${catName(item.category)}`}
                onPress={() => router.push(`/document/${item.id}?propertyId=${item.propertyId}`)}
              />
            </View>
          )}
          ListEmptyComponent={
            <EmptyState
              icon="checkmark-circle-outline"
              title={t('expiring.emptyTitle')}
              subtitle={t('expiring.emptySubtitle')}
            />
          }
        />
      )}
    </View>
  );
}

const styles = StyleSheet.create({
  chips: { gap: 8, paddingHorizontal: spacing[4], paddingVertical: spacing[2] },
  list: { padding: spacing[4], paddingTop: spacing[2], paddingBottom: spacing[9] },
});