import React from 'react';
import { Link, useNavigate } from 'react-router-dom';
import { AlertTriangle, ArrowRight, CalendarDays, Camera, Heart, 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 {
  TenantHeroCard,
  FrostedSurface,
  tenantHeroPrimaryButtonClass,
  tenantHeroSecondaryButtonClass,
  SectionCard,
  SectionHeader,
  StatCarousel,
  ActionGrid,
} from '../components/tenant';
import { cn } from '@/lib/utils';

import { AdminLayout } from '../components/AdminLayout';
import { getEvents, TenantEvent } from '../api';
import { isAuthError } from '../auth/tokens';
import { getApiErrorMessage } from '../lib/apiError';
import {
  adminPath,
  ADMIN_SETTINGS_PATH,
  ADMIN_WELCOME_BASE_PATH,
  ADMIN_EVENT_VIEW_PATH,
  ADMIN_EVENT_EDIT_PATH,
  ADMIN_EVENT_PHOTOS_PATH,
  ADMIN_EVENT_MEMBERS_PATH,
  ADMIN_EVENT_TASKS_PATH,
  ADMIN_EVENT_INVITES_PATH,
  ADMIN_EVENT_TOOLKIT_PATH,
} from '../constants';
import { buildLimitWarnings } from '../lib/limitWarnings';
import { useTranslation } from 'react-i18next';

export default function EventsPage() {
  const { t } = useTranslation('management');
  const { t: tCommon } = useTranslation('common');

  const [rows, setRows] = React.useState<TenantEvent[]>([]);
  const [loading, setLoading] = React.useState(true);
  const [error, setError] = React.useState<string | null>(null);
  const navigate = useNavigate();

  React.useEffect(() => {
    (async () => {
      try {
        setRows(await getEvents());
      } catch (err) {
        if (!isAuthError(err)) {
          setError(getApiErrorMessage(err, t('events.errors.loadFailed', 'Event konnte nicht geladen werden.')));
        }
      } finally {
        setLoading(false);
      }
    })();
  }, [t]);

  const translateManagement = React.useCallback(
    (key: string, fallback?: string, options?: Record<string, unknown>) =>
      t(key, { defaultValue: fallback, ...(options ?? {}) }),
    [t],
  );

  const translateCommon = React.useCallback(
    (key: string, fallback?: string, options?: Record<string, unknown>) =>
      tCommon(key, { defaultValue: fallback, ...(options ?? {}) }),
    [tCommon],
  );

  const totalEvents = rows.length;
  const publishedEvents = React.useMemo(
    () => rows.filter((event) => event.status === 'published').length,
    [rows],
  );
  const nextEvent = React.useMemo(() => {
    return (
      rows
        .filter((event) => event.event_date)
        .slice()
        .sort((a, b) => {
          const dateA = a.event_date ? new Date(a.event_date).getTime() : Infinity;
          const dateB = b.event_date ? new Date(b.event_date).getTime() : Infinity;
          return dateA - dateB;
        })[0] ?? null
    );
  }, [rows]);

  const statItems = React.useMemo(
    () => [
      {
        key: 'total',
        label: t('events.list.stats.total', 'Events gesamt'),
        value: totalEvents,
      },
      {
        key: 'published',
        label: t('events.list.stats.published', 'Veröffentlicht'),
        value: publishedEvents,
      },
      {
        key: 'drafts',
        label: t('events.list.stats.drafts', 'Entwürfe'),
        value: Math.max(0, totalEvents - publishedEvents),
      },
      nextEvent
        ? {
            key: 'next',
            label: t('events.list.stats.nextEvent', 'Nächstes Event'),
            value: formatDate(nextEvent.event_date),
          }
        : null,
    ].filter(Boolean) as { key: string; label: string; value: string | number }[],
    [t, totalEvents, publishedEvents, nextEvent],
  );
  const actionItems = React.useMemo(
    () => [
      {
        key: 'new',
        label: t('events.list.actions.create', 'Neues Event'),
        description: t('events.list.actions.createDescription', 'Starte mit einem frischen Setup.'),
        onClick: () => navigate(adminPath('/events/new')),
      },
      {
        key: 'welcome',
        label: t('events.list.actions.guidedSetup', 'Geführte Einrichtung'),
        description: t('events.list.actions.guidedSetupDescription', 'Springe zurück in den Onboarding-Flow.'),
        onClick: () => navigate(ADMIN_WELCOME_BASE_PATH),
      },
      {
        key: 'settings',
        label: t('events.list.actions.settings', 'Einstellungen öffnen'),
        description: t('events.list.actions.settingsDescription', 'Passe Farben, Branding und Aufgabenpakete an.'),
        onClick: () => navigate(ADMIN_SETTINGS_PATH),
      },
    ],
    [t, navigate],
  );

  const pageTitle = translateManagement('events.list.title', 'Deine Events');
  const pageSubtitle = translateManagement(
    'events.list.subtitle',
    'Plane Momente, die in Erinnerung bleiben. Hier verwaltest du alles rund um deine Veranstaltungen.'
  );
  const heroDescription = t(
    'events.list.hero.description',
    'Aktiviere Storytelling, Moderation und Galerie-Workflows für jeden Anlass in wenigen Minuten.'
  );
  const heroSummaryCopy = totalEvents > 0
    ? t('events.list.hero.summary', ':count Events aktiv verwaltet – halte Aufgaben und Uploads im Blick.', { count: totalEvents })
    : t('events.list.hero.summary_empty', 'Noch keine Events – starte jetzt mit deinem ersten Konzept.');
  const heroSecondaryCopy = t(
    'events.list.hero.secondary',
    'Erstelle Events im Admin, begleite Gäste live vor Ort und prüfe Kennzahlen im Marketing-Dashboard.'
  );
  const heroBadge = t('events.list.badge.dashboard', 'Tenant Dashboard');
  const heroPrimaryAction = (
    <Button
      size="sm"
      className={tenantHeroPrimaryButtonClass}
      onClick={() => navigate(adminPath('/events/new'))}
    >
      {t('events.list.actions.create', 'Neues Event')}
    </Button>
  );
  const heroSecondaryAction = (
    <Button size="sm" className={tenantHeroSecondaryButtonClass} asChild>
      <Link to={ADMIN_SETTINGS_PATH}>
        {t('events.list.actions.settings', 'Einstellungen')}
        <ArrowRight className="ml-2 h-4 w-4" />
      </Link>
    </Button>
  );
  const heroAside = (
    <FrostedSurface className="w-full rounded-2xl border-slate-200 bg-white p-5 text-slate-900 shadow-lg shadow-pink-200/20 dark:border-white/20 dark:bg-white/10">
      <div className="space-y-4">
        <div>
          <p className="text-xs uppercase tracking-wide text-slate-500">
            {t('events.list.hero.published_label', 'Veröffentlichte Events')}
          </p>
          <p className="mt-1 text-2xl font-semibold text-slate-900">{publishedEvents}</p>
          <p className="text-xs text-slate-500">
            {t('events.list.hero.total_label', ':count insgesamt', { count: totalEvents })}
          </p>
        </div>
        {nextEvent ? (
          <div className="rounded-xl border border-pink-100 bg-pink-50/70 p-4 text-slate-900 shadow-inner shadow-pink-200/50">
            <p className="text-xs uppercase tracking-wide text-pink-600">
              {t('events.list.hero.next_label', 'Nächstes Event')}
            </p>
            <p className="mt-1 text-sm font-semibold">{renderName(nextEvent.name)}</p>
            <p className="text-xs text-slate-600">{formatDate(nextEvent.event_date)}</p>
            {nextEvent.slug ? (
              <Button
                variant="ghost"
                size="sm"
                className="mt-3 h-8 justify-start px-3 text-pink-600 hover:bg-pink-100"
                onClick={() => navigate(ADMIN_EVENT_VIEW_PATH(nextEvent.slug))}
              >
                {t('events.list.hero.open_event', 'Event öffnen')}
                <ArrowRight className="ml-2 h-4 w-4" />
              </Button>
            ) : null}
          </div>
        ) : (
          <p className="rounded-xl border border-dashed border-pink-200/70 bg-white/70 p-4 text-xs text-slate-600">
            {t('events.list.hero.no_upcoming', 'Plane ein Datum, um hier die nächste Station zu sehen.')}
          </p>
        )}
      </div>
    </FrostedSurface>
  );
  const draftEvents = totalEvents - publishedEvents;
  const [statusFilter, setStatusFilter] = React.useState<'all' | 'published' | 'draft'>('all');
  const filteredRows = React.useMemo(() => {
    if (statusFilter === 'published') {
      return rows.filter((event) => event.status === 'published');
    }
    if (statusFilter === 'draft') {
      return rows.filter((event) => event.status !== 'published');
    }
    return rows;
  }, [rows, statusFilter]);
  const overviewDescription = React.useMemo(() => {
    if (loading) {
      return t('events.list.overview.loading', 'Wir sammeln gerade deine Event-Details …');
    }
    if (filteredRows.length === 0) {
      if (statusFilter === 'published') {
        return t('events.list.overview.empty_published', 'Noch keine veröffentlichten Events.');
      }
      if (statusFilter === 'draft') {
        return t('events.list.overview.empty_drafts', 'Keine Entwürfe – nutze die Zeit für dein nächstes Event.');
      }
      return t('events.list.overview.empty', 'Noch keine Events - starte jetzt und lege dein erstes Event an.');
    }
    return t('events.list.overview.count', '{{count}} Events aktiv verwaltet.', { count: filteredRows.length });
  }, [filteredRows.length, loading, statusFilter, t]);
  const filterOptions: Array<{ key: 'all' | 'published' | 'draft'; label: string; count: number }> = [
    { key: 'all', label: t('events.list.filters.all', 'Alle'), count: totalEvents },
    { key: 'published', label: t('events.list.filters.published', 'Live'), count: publishedEvents },
    { key: 'draft', label: t('events.list.filters.drafts', 'Entwürfe'), count: Math.max(0, draftEvents) },
  ];

  return (
    <AdminLayout title={pageTitle} subtitle={pageSubtitle}>
      {error && (
        <Alert variant="destructive">
          <AlertTitle>Fehler beim Laden</AlertTitle>
          <AlertDescription>{error}</AlertDescription>
        </Alert>
      )}

      <TenantHeroCard
        badge={heroBadge}
        title={pageTitle}
        description={heroDescription}
        supporting={[heroSummaryCopy, heroSecondaryCopy]}
        primaryAction={heroPrimaryAction}
        secondaryAction={heroSecondaryAction}
        aside={heroAside}
      />

      <SectionCard className="space-y-4">
        <SectionHeader
          eyebrow={t('events.list.badge', 'Events')}
          title={t('events.list.overview.title', 'Übersicht')}
          description={overviewDescription}
          endSlot={(
            <button
              type="button"
              className="rounded-full border border-slate-200 bg-white px-4 py-1.5 text-xs font-semibold uppercase tracking-wide text-slate-800 shadow-inner shadow-white/20 dark:border-white/15 dark:bg-white/10 dark:text-white"
            >
              {t('events.list.badge.dashboard', 'Tenant Dashboard')}
            </button>
          )}
        />
        <StatCarousel items={statItems} />
        <ActionGrid items={actionItems} columns={1} />
        <div className="flex gap-2 overflow-x-auto pb-1">
          {filterOptions.map((option) => (
            <button
              key={option.key}
              type="button"
              onClick={() => setStatusFilter(option.key)}
              className={cn(
                'flex items-center gap-2 rounded-full border px-4 py-1.5 text-xs font-semibold transition',
                statusFilter === option.key
                  ? 'border-rose-200 bg-rose-50 text-rose-700 shadow shadow-rose-100/40 dark:border-white/60 dark:bg-white/10 dark:text-white'
                  : 'border-slate-200 text-slate-600 hover:text-slate-900 dark:border-white/15 dark:text-slate-300 dark:hover:text-white'
              )}
            >
              {option.label}
              <span className="text-[11px] text-slate-400 dark:text-slate-500">{option.count}</span>
            </button>
          ))}
        </div>
        {loading ? (
          <LoadingState />
        ) : filteredRows.length === 0 ? (
          <EmptyState
            title={t('events.list.empty.title', 'Noch kein Event angelegt')}
            description={t(
              'events.list.empty.description',
              'Starte jetzt mit deinem ersten Event und lade Gäste in dein farbenfrohes Erlebnisportal ein.'
            )}
            onCreate={() => navigate(adminPath('/events/new'))}
          />
        ) : (
          <div className="space-y-3">
            {filteredRows.map((event) => (
              <EventCard
                key={event.id}
                event={event}
                translate={translateManagement}
                translateCommon={translateCommon}
              />
            ))}
          </div>
        )}
      </SectionCard>
    </AdminLayout>
  );
}

function EventCard({
  event,
  translate,
  translateCommon,
}: {
  event: TenantEvent;
  translate: (key: string, fallback?: string, options?: Record<string, unknown>) => string;
  translateCommon: (key: string, fallback?: string, options?: Record<string, unknown>) => string;
}) {
  const slug = event.slug;
  const isPublished = event.status === 'published';
  const photoCount = event.photo_count ?? 0;
  const likeCount = event.like_count ?? 0;
  const limitWarnings = React.useMemo(
    () => buildLimitWarnings(event.limits ?? null, (key, opts) => translateCommon(`limits.${key}`, undefined, opts)),
    [event.limits, translateCommon],
  );
  const metaItems = [
    {
      key: 'date',
      label: translate('events.list.meta.date', 'Eventdatum'),
      value: formatDate(event.event_date),
      icon: <CalendarDays className="h-4 w-4 text-rose-500" />,
    },
    {
      key: 'photos',
      label: translate('events.list.meta.photos', 'Uploads'),
      value: photoCount,
      icon: <Camera className="h-4 w-4 text-fuchsia-500" />,
    },
    {
      key: 'likes',
      label: translate('events.list.meta.likes', 'Likes'),
      value: likeCount,
      icon: <Heart className="h-4 w-4 text-amber-500" />,
    },
  ];
  const secondaryLinks = [
    { key: 'edit', label: translateCommon('actions.edit', 'Bearbeiten'), to: ADMIN_EVENT_EDIT_PATH(slug) },
    { key: 'members', label: translate('events.list.actions.members', 'Mitglieder'), to: ADMIN_EVENT_MEMBERS_PATH(slug) },
    { key: 'tasks', label: translate('events.list.actions.tasks', 'Tasks'), to: ADMIN_EVENT_TASKS_PATH(slug) },
    { key: 'invites', label: translate('events.list.actions.invites', 'QR-Einladungen'), to: ADMIN_EVENT_INVITES_PATH(slug) },
    { key: 'toolkit', label: translate('events.list.actions.toolkit', 'Toolkit'), to: ADMIN_EVENT_TOOLKIT_PATH(slug) },
  ];

  return (
    <FrostedSurface className="space-y-4 rounded-3xl p-5 shadow-lg shadow-rose-100/30 transition hover:-translate-y-0.5 hover:shadow-rose-200/60">
      <div className="flex flex-col gap-3 sm:flex-row sm:items-start sm:justify-between">
        <div>
          <p className="text-xs uppercase tracking-[0.3em] text-rose-300/80">{translate('events.list.item.label', 'Event')}</p>
          <h3 className="text-xl font-semibold text-slate-900">{renderName(event.name)}</h3>
        </div>
        <Badge className={isPublished ? 'bg-emerald-500/90 text-white shadow shadow-emerald-500/30' : 'bg-slate-200 text-slate-700'}>
          {isPublished
            ? translateCommon('events.status.published', 'Veröffentlicht')
            : translateCommon('events.status.draft', 'Entwurf')}
        </Badge>
      </div>

      <div className="-mx-1 flex snap-x snap-mandatory gap-3 overflow-x-auto px-1">
        {metaItems.map((item) => (
          <MetaChip key={item.key} icon={item.icon} label={item.label} value={item.value} />
        ))}
      </div>

      {limitWarnings.length > 0 && (
        <div className="space-y-2">
          {limitWarnings.map((warning) => (
            <div
              key={warning.id}
              className={cn(
                'flex items-start gap-2 rounded-2xl border p-3 text-xs',
                warning.tone === 'danger'
                  ? 'border-rose-200/60 bg-rose-50 text-rose-900'
                  : 'border-amber-200/60 bg-amber-50 text-amber-900',
              )}
            >
              <AlertTriangle className="h-4 w-4" />
              <span>{warning.message}</span>
            </div>
          ))}
        </div>
      )}

      <div className="grid gap-2 sm:grid-cols-2">
        <Button
          asChild
          className="rounded-full bg-brand-rose text-white shadow shadow-rose-400/40 hover:bg-brand-rose/90"
        >
          <Link to={ADMIN_EVENT_VIEW_PATH(slug)}>
            {translateCommon('actions.open', 'Öffnen')} <ArrowRight className="ml-2 h-4 w-4" />
          </Link>
        </Button>
        <Button asChild variant="outline" className="rounded-full border-rose-200 text-rose-600 hover:bg-rose-50">
          <Link to={ADMIN_EVENT_PHOTOS_PATH(slug)}>
            {translate('events.list.actions.photos', 'Fotos moderieren')}
          </Link>
        </Button>
      </div>

      <div className="flex flex-wrap gap-2">
        {secondaryLinks.map((action) => (
          <ActionChip key={action.key} to={action.to}>
            {action.label}
          </ActionChip>
        ))}
      </div>
    </FrostedSurface>
  );
}

function MetaChip({
  icon,
  label,
  value,
}: {
  icon: React.ReactNode;
  label: string;
  value: string | number;
}) {
  return (
    <div className="min-w-[55%] snap-center rounded-2xl border border-slate-200 bg-white p-3 text-left text-xs shadow-sm sm:min-w-0 dark:border-white/15 dark:bg-white/10 dark:text-white">
      <div className="flex items-center gap-2 text-slate-500 dark:text-slate-300">
        {icon}
        <span>{label}</span>
      </div>
      <p className="mt-1 text-sm font-semibold text-slate-900 dark:text-white">{value}</p>
    </div>
  );
}

function ActionChip({ to, children }: { to: string; children: React.ReactNode }) {
  return (
    <Link
      to={to}
      className="inline-flex items-center rounded-full border border-slate-200 px-3 py-1.5 text-xs font-semibold text-slate-600 transition hover:border-rose-200 hover:bg-rose-50 hover:text-rose-700 dark:border-white/15 dark:text-slate-300 dark:hover:border-white/40 dark:hover:bg-white/10 dark:hover:text-white"
    >
      {children}
    </Link>
  );
}

function LoadingState() {
  return (
    <div className="space-y-3">
      {Array.from({ length: 3 }).map((_, index) => (
        <FrostedSurface
          key={index}
          className="h-24 animate-pulse rounded-3xl bg-gradient-to-r from-white/20 via-white/60 to-white/20"
        />
      ))}
    </div>
  );
}

function EmptyState({
  title,
  description,
  onCreate,
}: {
  title: string;
  description: string;
  onCreate: () => void;
}) {
  return (
    <FrostedSurface className="flex flex-col items-center justify-center gap-4 border-dashed border-pink-200/70 p-10 text-center">
      <div className="rounded-full bg-pink-100 p-3 text-pink-600 shadow-inner shadow-pink-200/80">
        <Plus className="h-5 w-5" />
      </div>
      <div className="space-y-2">
        <h3 className="text-lg font-semibold text-slate-900">{title}</h3>
        <p className="text-sm text-slate-600">{description}</p>
      </div>
      <Button
        onClick={onCreate}
        className="rounded-full bg-gradient-to-r from-pink-500 via-fuchsia-500 to-purple-500 px-6 text-white shadow-lg shadow-pink-500/20"
      >
        <Plus className="mr-1 h-4 w-4" /> Event erstellen
      </Button>
    </FrostedSurface>
  );
}

function formatDate(iso: string | null): string {
  if (!iso) return 'Noch kein Datum';
  const date = new Date(iso);
  if (Number.isNaN(date.getTime())) {
    return 'Unbekanntes Datum';
  }
  return date.toLocaleDateString('de-DE', {
    day: '2-digit',
    month: 'short',
    year: 'numeric',
  });
}

function renderName(name: TenantEvent['name']): string {
  if (typeof name === 'string') return name;
  if (name && typeof name === 'object') {
    return name.de ?? name.en ?? Object.values(name)[0] ?? 'Unbenanntes Event';
  }
  return 'Unbenanntes Event';
}