import React, { useMemo, useState } from 'react';
import { FlatList, ScrollView, StyleSheet, View } from 'react-native';
import { useLocalSearchParams, useRouter } from 'expo-router';
import { useQuery } from '@tanstack/react-query';
import { api, DocCategory, Document } from '@/api';
import { useT } from '@/i18n';
import { AppBar } from '@/components/AppBar';
import { Chip, EmptyState, IconButton, Loading } from '@/components/ui';
import { DocumentRow } from '@/components/domain';
import { colors, spacing } from '@/theme';

type StatusFilter = 'all' | 'attention' | 'valid' | 'expiring' | 'expired';

const STATUSES: StatusFilter[] = ['all', 'attention', 'valid', 'expiring', 'expired'];

export default function DocumentsScreen() {
  const { propertyId, category, status: initialStatus } = useLocalSearchParams<{
    propertyId: string;
    category?: string;
    status?: string;
  }>();
  const pid = Number(propertyId);
  const router = useRouter();
  const t = useT();
  // Links can preselect a filter (e.g. the "needs attention" banner).
  const [status, setStatus] = useState<StatusFilter>(
    STATUSES.includes(initialStatus as StatusFilter) ? (initialStatus as StatusFilter) : 'all',
  );

  const docsQuery = useQuery({ queryKey: ['documents', pid], queryFn: () => api.documents.listByProperty(pid) });
  const propertyQuery = useQuery({ queryKey: ['property', pid], queryFn: () => api.properties.get(pid) });
  const catsQuery = useQuery({ queryKey: ['categories'], queryFn: () => api.reference.categories() });

  const categories: DocCategory[] = catsQuery.data ?? [];
  const catName = (slug: string) => categories.find((c) => c.slug === slug)?.name ?? slug;

  const inCategory = useMemo<Document[]>(
    () => ((docsQuery.data ?? []) as Document[]).filter((d) => !category || d.category === category),
    [docsQuery.data, category],
  );

  const counts = useMemo(() => {
    const c = { all: inCategory.length, attention: 0, valid: 0, expiring: 0, expired: 0 };
    for (const d of inCategory) {
      if (d.expiryStatus === 'valid') c.valid += 1;
      else if (d.expiryStatus === 'expiring') c.expiring += 1;
      else if (d.expiryStatus === 'expired') c.expired += 1;
    }
    c.attention = c.expiring + c.expired;
    return c;
  }, [inCategory]);

  const visible = useMemo(() => {
    if (status === 'all') return inCategory;
    if (status === 'attention') {
      return inCategory.filter((d) => d.expiryStatus === 'expiring' || d.expiryStatus === 'expired');
    }
    return inCategory.filter((d) => d.expiryStatus === status);
  }, [inCategory, status]);

  const title = category ? catName(category) : t('documents.allTitle');
  const subtitle = `${propertyQuery.data?.name ?? ''} · ${t('properties.docCount', { count: inCategory.length })}`;

  return (
    <View style={{ flex: 1, backgroundColor: colors.bgApp }}>
      <AppBar
        title={title}
        subtitle={subtitle}
        back
        right={<IconButton name="search" onPress={() => router.push('/search')} />}
      />

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

      {docsQuery.isLoading ? (
        <Loading />
      ) : (
        <FlatList
          data={visible as Document[]}
          keyExtractor={(d) => String(d.id)}
          contentContainerStyle={styles.list}
          renderItem={({ item }) => (
            <View style={{ marginBottom: spacing[3] }}>
              <DocumentRow
                document={item}
                categoryName={catName(item.category)}
                showCategory={!category}
                onPress={() => router.push(`/document/${item.id}?propertyId=${pid}`)}
              />
            </View>
          )}
          ListEmptyComponent={
            <EmptyState icon="documents-outline" title={t('documents.emptyTitle')} subtitle={t('documents.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] },
});