import React from 'react';
import { useNavigate } from 'react-router-dom';
import { useTranslation } from 'react-i18next';
import { format } from 'date-fns';
import type { Locale } from 'date-fns';
import { de, enGB } from 'date-fns/locale';
import { Layers, Library, Loader2, Plus } from 'lucide-react';

import { Alert, AlertDescription, AlertTitle } from '@/components/ui/alert';
import { Badge } from '@/components/ui/badge';
import { Button } from '@/components/ui/button';
import { Card, CardContent, CardDescription, CardFooter, CardHeader, CardTitle } from '@/components/ui/card';
import { Dialog, DialogContent, DialogFooter, DialogHeader, DialogTitle } from '@/components/ui/dialog';
import { Input } from '@/components/ui/input';
import { Label } from '@/components/ui/label';
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select';

import { AdminLayout } from '../components/AdminLayout';
import {
  getTaskCollections,
  importTaskCollection,
  getEvents,
  PaginationMeta,
  TenantEvent,
  TenantTaskCollection,
} from '../api';
import { buildEngagementTabPath } from '../constants';
import { isAuthError } from '../auth/tokens';
import toast from 'react-hot-toast';

const DEFAULT_PAGE_SIZE = 12;

type ScopeFilter = 'all' | 'global' | 'tenant';

type CollectionsState = {
  items: TenantTaskCollection[];
  meta: PaginationMeta | null;
};

export type TaskCollectionsSectionProps = {
  embedded?: boolean;
  onNavigateToTasks?: () => void;
};

export function TaskCollectionsSection({ embedded = false, onNavigateToTasks }: TaskCollectionsSectionProps) {
  const navigate = useNavigate();
  const { t, i18n } = useTranslation('management');

  const [collectionsState, setCollectionsState] = React.useState<CollectionsState>({ items: [], meta: null });
  const [page, setPage] = React.useState(1);
  const [search, setSearch] = React.useState('');
  const [scope, setScope] = React.useState<ScopeFilter>('all');
  const [loading, setLoading] = React.useState(true);
  const [error, setError] = React.useState<string | null>(null);

  const [dialogOpen, setDialogOpen] = React.useState(false);
  const [selectedCollection, setSelectedCollection] = React.useState<TenantTaskCollection | null>(null);
  const [events, setEvents] = React.useState<TenantEvent[]>([]);
  const [selectedEventSlug, setSelectedEventSlug] = React.useState('');
  const [importing, setImporting] = React.useState(false);
  const [eventsLoading, setEventsLoading] = React.useState(false);
  const [eventError, setEventError] = React.useState<string | null>(null);
  const [reloadToken, setReloadToken] = React.useState(0);

  const scopeParam = React.useMemo(() => {
    if (scope === 'global') return 'global';
    if (scope === 'tenant') return 'tenant';
    return undefined;
  }, [scope]);

  React.useEffect(() => {
    let cancelled = false;
    async function loadCollections() {
      setLoading(true);
      setError(null);
      try {
        const result = await getTaskCollections({
          page,
          per_page: DEFAULT_PAGE_SIZE,
          search: search.trim() || undefined,
          scope: scopeParam,
        });
        if (cancelled) return;
        setCollectionsState({ items: result.data, meta: result.meta });
      } catch (err) {
        if (cancelled) return;
        if (!isAuthError(err)) {
          setError(t('collections.notifications.error'));
          toast.error(t('collections.notifications.error'));
        }
      } finally {
        if (!cancelled) {
          setLoading(false);
        }
      }
    }

    void loadCollections();

    return () => {
      cancelled = true;
    };
  }, [page, search, scopeParam, reloadToken, t]);

  async function ensureEventsLoaded() {
    if (events.length > 0 || eventsLoading) {
      return;
    }
    setEventsLoading(true);
    setEventError(null);
    try {
      const result = await getEvents();
      setEvents(result);
    } catch (err) {
      if (!isAuthError(err)) {
        setEventError(t('collections.errors.eventsLoad'));
      }
    } finally {
      setEventsLoading(false);
    }
  }

  function openImportDialog(collection: TenantTaskCollection) {
    setSelectedCollection(collection);
    setSelectedEventSlug('');
    setDialogOpen(true);
    void ensureEventsLoaded();
  }

  async function handleImport(event: React.FormEvent<HTMLFormElement>) {
    event.preventDefault();
    if (!selectedCollection || !selectedEventSlug) {
      setEventError(t('collections.errors.selectEvent'));
      return;
    }
    setImporting(true);
    setEventError(null);
    try {
      await importTaskCollection(selectedCollection.id, selectedEventSlug);
      toast.success(t('collections.notifications.imported'));
      setDialogOpen(false);
      setReloadToken((token) => token + 1);
    } catch (err) {
      if (!isAuthError(err)) {
        setEventError(t('collections.notifications.error'));
        toast.error(t('collections.notifications.error'));
      }
    } finally {
      setImporting(false);
    }
  }

  const showEmpty = !loading && collectionsState.items.length === 0;
  const locale = i18n.language.startsWith('en') ? enGB : de;

  const title = t('collections.title') ?? 'Task Collections';
  const subtitle = embedded
    ? t('collections.subtitle') ?? ''
    : t('collections.subtitle') ?? '';

  const navigateToTasks = React.useCallback(() => {
    if (onNavigateToTasks) {
      onNavigateToTasks();
      return;
    }
    navigate(buildEngagementTabPath('tasks'));
  }, [navigate, onNavigateToTasks]);

  return (
    <div className="space-y-6">
      {error && (
        <Alert variant="destructive">
          <AlertTitle>{t('collections.notifications.error')}</AlertTitle>
          <AlertDescription>{error}</AlertDescription>
        </Alert>
      )}

      <Card className="border-0 bg-white/85 shadow-xl shadow-pink-100/60">
        <CardHeader className="flex flex-col gap-4 sm:flex-row sm:items-start sm:justify-between">
          <div>
            <CardTitle className="flex items-center gap-2 text-xl text-slate-900">
              <Layers className="h-5 w-5 text-pink-500" />
              {title}
            </CardTitle>
            <CardDescription className="text-sm text-slate-600">{subtitle}</CardDescription>
          </div>
          <div className="flex flex-wrap gap-2">
            <Button variant="outline" onClick={navigateToTasks}>
              <Library className="mr-2 h-4 w-4" />
              {t('collections.actions.openTasks')}
            </Button>
            <Button
              className="bg-gradient-to-r from-pink-500 via-fuchsia-500 to-purple-500 text-white shadow-lg shadow-pink-500/20"
              onClick={() => setScope('tenant')}
            >
              {t('collections.scope.tenant')}
            </Button>
          </div>
        </CardHeader>
        <CardContent className="space-y-6">
          <div className="grid gap-3 md:grid-cols-[minmax(0,1fr),220px]">
            <Input
              placeholder={t('collections.filters.search') ?? 'Nach Vorlagen suchen'}
              value={search}
              onChange={(event) => {
                setPage(1);
                setSearch(event.target.value);
              }}
            />
            <Select value={scope} onValueChange={(value: ScopeFilter) => { setPage(1); setScope(value); }}>
              <SelectTrigger>
                <SelectValue placeholder={t('collections.filters.allScopes')} />
              </SelectTrigger>
              <SelectContent>
                <SelectItem value="all">{t('collections.filters.allScopes')}</SelectItem>
                <SelectItem value="tenant">{t('collections.filters.tenantOnly')}</SelectItem>
                <SelectItem value="global">{t('collections.filters.globalOnly')}</SelectItem>
              </SelectContent>
            </Select>
          </div>

          {loading ? (
            <CollectionsSkeleton />
          ) : showEmpty ? (
            <EmptyCollectionsState onCreate={navigateToTasks} />
          ) : (
            <div className="grid gap-4 md:grid-cols-2 xl:grid-cols-3">
              {collectionsState.items.map((collection) => (
                <TaskCollectionCard
                  key={collection.id}
                  collection={collection}
                  locale={locale}
                  onImport={() => openImportDialog(collection)}
                  onNavigateToTasks={navigateToTasks}
                />
              ))}
            </div>
          )}

          {collectionsState.meta && collectionsState.meta.last_page > 1 ? (
            <div className="flex flex-wrap items-center justify-between gap-2 border-t border-slate-100 pt-4 text-sm">
              <div className="text-slate-500">
                {t('collections.pagination.page', {
                  current: collectionsState.meta.current_page ?? 1,
                  total: collectionsState.meta.last_page ?? 1,
                })}
              </div>
              <div className="flex gap-2">
                <Button
                  variant="outline"
                  size="sm"
                  onClick={() => setPage((value) => Math.max(value - 1, 1))}
                  disabled={(collectionsState.meta.current_page ?? 1) <= 1}
                >
                  {t('collections.pagination.prev')}
                </Button>
                <Button
                  variant="outline"
                  size="sm"
                  onClick={() => setPage((value) => Math.min(value + 1, collectionsState.meta?.last_page ?? value + 1))}
                  disabled={(collectionsState.meta.current_page ?? 1) >= (collectionsState.meta.last_page ?? 1)}
                >
                  {t('collections.pagination.next')}
                </Button>
              </div>
            </div>
          ) : null}
        </CardContent>
      </Card>

      <ImportCollectionDialog
        open={dialogOpen}
        onOpenChange={setDialogOpen}
        collection={selectedCollection}
        events={events}
        eventsLoading={eventsLoading}
        selectedEventSlug={selectedEventSlug}
        onSelectedEventChange={setSelectedEventSlug}
        onSubmit={handleImport}
        importing={importing}
        error={eventError}
        locale={locale}
      />
    </div>
  );
}

export default function TaskCollectionsPage() {
  const navigate = useNavigate();
  const { t } = useTranslation('management');
  return (
    <AdminLayout
      title={t('collections.title') ?? 'Task Collections'}
      subtitle={t('collections.subtitle') ?? ''}
    >
      <TaskCollectionsSection onNavigateToTasks={() => navigate(buildEngagementTabPath('tasks'))} />
    </AdminLayout>
  );
}

function TaskCollectionCard({
  collection,
  locale,
  onImport,
  onNavigateToTasks,
}: {
  collection: TenantTaskCollection;
  locale: Locale;
  onImport: () => void;
  onNavigateToTasks: () => void;
}) {
  const { t } = useTranslation('management');
  const updatedAt = collection.updated_at ? format(new Date(collection.updated_at), 'Pp', { locale }) : null;
  return (
    <Card className="border border-slate-200/70 bg-white/85 shadow-md shadow-pink-100/20">
      <CardHeader>
        <CardTitle className="text-base text-slate-900">{collection.name}</CardTitle>
        {collection.description ? (
          <CardDescription className="text-xs text-slate-500">{collection.description}</CardDescription>
        ) : null}
      </CardHeader>
      <CardContent className="space-y-3 text-sm text-slate-600">
        <div className="flex flex-wrap gap-2">
          <Badge variant={collection.is_global ? 'secondary' : 'default'}>
            {collection.is_global ? t('collections.scope.global') : t('collections.scope.tenant')}
          </Badge>
          <Badge variant="outline">{t('collections.labels.taskCount', { count: collection.tasks_count })}</Badge>
          {collection.event_type ? (
            <Badge variant="outline">{collection.event_type.name}</Badge>
          ) : null}
        </div>
        {updatedAt ? (
          <p className="text-xs text-slate-400">{t('collections.labels.updated', { date: updatedAt })}</p>
        ) : null}
      </CardContent>
      <CardFooter className="flex flex-wrap gap-2">
        <Button className="bg-gradient-to-r from-pink-500 via-fuchsia-500 to-purple-500 text-white" onClick={onImport}>
          <Plus className="mr-1 h-4 w-4" />
          {t('collections.actions.import')}
        </Button>
        <Button variant="outline" onClick={onNavigateToTasks}>
          {t('collections.actions.openTasks')}
        </Button>
      </CardFooter>
    </Card>
  );
}

function ImportCollectionDialog({
  open,
  onOpenChange,
  collection,
  events,
  eventsLoading,
  selectedEventSlug,
  onSelectedEventChange,
  onSubmit,
  importing,
  error,
  locale,
}: {
  open: boolean;
  onOpenChange: (open: boolean) => void;
  collection: TenantTaskCollection | null;
  events: TenantEvent[];
  eventsLoading: boolean;
  selectedEventSlug: string;
  onSelectedEventChange: (slug: string) => void;
  onSubmit: (event: React.FormEvent<HTMLFormElement>) => void;
  importing: boolean;
  error: string | null;
  locale: Locale;
}) {
  const { t } = useTranslation('management');
  return (
    <Dialog open={open} onOpenChange={onOpenChange}>
      <DialogContent>
        <DialogHeader>
          <DialogTitle>{t('collections.dialogs.importTitle')}</DialogTitle>
        </DialogHeader>
        <form onSubmit={onSubmit} className="space-y-4">
          <div className="space-y-1">
            <Label>{t('collections.dialogs.collectionLabel')}</Label>
            <p className="rounded-md border border-slate-200 bg-slate-50 px-3 py-2 text-sm text-slate-600">
              {collection?.name ?? 'Unbekannte Sammlung'}
            </p>
          </div>
          <div className="space-y-2">
            <Label htmlFor="collection-event">{t('collections.dialogs.selectEvent')}</Label>
            <Select value={selectedEventSlug} onValueChange={onSelectedEventChange} disabled={eventsLoading || !events.length}>
              <SelectTrigger id="collection-event">
                <SelectValue placeholder={eventsLoading ? t('collections.errors.eventsLoad') : t('collections.dialogs.selectEvent')} />
              </SelectTrigger>
              <SelectContent>
                {events.map((event) => {
                  const eventDate = event.event_date ? format(new Date(event.event_date), 'PPP', { locale }) : null;
                  return (
                    <SelectItem key={event.slug} value={event.slug}>
                      {event.name && typeof event.name === 'string' ? event.name : event.slug}
                      {eventDate ? ` · ${eventDate}` : ''}
                    </SelectItem>
                  );
                })}
              </SelectContent>
            </Select>
            {error ? <p className="text-xs text-rose-600">{error}</p> : null}
          </div>
          <DialogFooter className="flex gap-2">
            <Button type="button" variant="outline" onClick={() => onOpenChange(false)}>
              {t('collections.dialogs.cancel')}
            </Button>
            <Button type="submit" disabled={importing || !selectedEventSlug}>
              {importing ? <Loader2 className="mr-2 h-4 w-4 animate-spin" /> : null}
              {t('collections.dialogs.submit')}
            </Button>
          </DialogFooter>
        </form>
      </DialogContent>
    </Dialog>
  );
}

function CollectionsSkeleton() {
  return (
    <div className="grid gap-4 md:grid-cols-2 xl:grid-cols-3">
      {Array.from({ length: 6 }).map((_, index) => (
        <div key={`collection-skeleton-${index}`} className="h-40 animate-pulse rounded-xl bg-gradient-to-r from-white/40 via-white/60 to-white/40" />
      ))}
    </div>
  );
}

function EmptyCollectionsState({ onCreate }: { onCreate: () => void }) {
  const { t } = useTranslation('management');
  return (
    <div className="flex flex-col items-center justify-center gap-3 rounded-xl border border-dashed border-slate-200 bg-slate-50/60 p-10 text-center">
      <h3 className="text-base font-semibold text-slate-800">{t('collections.empty.title')}</h3>
      <p className="text-sm text-slate-500">{t('collections.empty.description')}</p>
      <Button onClick={onCreate} className="bg-gradient-to-r from-pink-500 via-fuchsia-500 to-purple-500 text-white">
        <Plus className="mr-1 h-4 w-4" />
        {t('collections.actions.create')}
      </Button>
    </div>
  );
}