import Link from 'next/link';

import { auth } from '@/lib/auth';
import { prisma } from '@/lib/db';
import { deviceHealth, humaniseSeconds } from '@/lib/device/health';
import { toCivilDate } from '@/lib/schedule/civil';
import { loadScheduleContext, loadSettings } from '@/lib/schedule/context';
import { formatDateFr, formatHoursText, formatNextChangeFr } from '@/lib/schedule/format';
import { getCurrentStatus, resolveWeek } from '@/lib/schedule/resolver';

import ScreenPreview from './ScreenPreview';

export const metadata = { title: 'Tableau de bord — ITA ITO' };

export default async function AdminHome() {
  const now = new Date();
  const [session, settings] = await Promise.all([auth(), loadSettings()]);
  const context = await loadScheduleContext(now, settings);

  const status = getCurrentStatus(now, context);
  const week = resolveWeek(now, context);
  const today = toCivilDate(now, settings.timezone);

  const [device, failedTranslations, holidaySync] = await Promise.all([
    prisma.device.findFirst({ where: { isActive: true }, orderBy: { lastSeenAt: 'desc' } }),
    prisma.message.count({ where: { translationStatus: 'ERROR' } }),
    prisma.syncState.findUnique({ where: { key: 'holidays' } }),
  ]);

  const health = device ? deviceHealth(device, now) : null;
  const isOpen = status.status === 'OPEN' || status.status === 'CLOSING_SOON';

  const alerts: { text: string; href?: string }[] = [];
  if (!device) {
    alerts.push({ text: 'Aucun écran appairé. Suivez la procédure d’appairage du README.' });
  } else if (health?.neverSeen) {
    alerts.push({ text: 'L’écran est enregistré mais ne s’est jamais manifesté.' });
  } else if (health?.isOverdue) {
    const silentFor = humaniseSeconds(secondsSince(device.lastSeenAt, now));
    alerts.push({
      text: `L’écran n’a pas donné signe de vie ${silentFor}. Vérifiez la batterie et le Wi-Fi.`,
    });
  }
  if (failedTranslations > 0) {
    alerts.push({
      text: `${failedTranslations} message${failedTranslations > 1 ? 's' : ''} sans traduction anglaise.`,
      href: '/admin/messages',
    });
  }
  if (holidaySync?.lastErrorAt) {
    alerts.push({
      text: `La synchronisation des jours fériés a échoué : ${holidaySync.lastError ?? 'raison inconnue'}.`,
      href: '/admin/feries',
    });
  }

  return (
    <main className="mx-auto max-w-4xl px-4 py-10">
      <h1 className="text-2xl">Tableau de bord</h1>
      <p className="mt-1 text-sm text-[var(--ink-muted)]">
        {/* The header hides the address on a narrow screen to save room, so it
            belongs here: every change is signed with it in the audit trail,
            and several people share the shop's phone. */}
        Connecté en tant que {session?.user?.email}
        {session?.user?.role === 'admin' ? '' : ' — lecture seule'}.
      </p>

      {alerts.length > 0 ? (
        <ul className="mt-4 space-y-2">
          {alerts.map((alert) => (
            <li
              key={alert.text}
              className="rounded-[var(--radius-md)] border border-[var(--danger)] bg-[var(--danger-tint)] px-4 py-3 text-sm text-[var(--danger)]"
            >
              {alert.href ? (
                <Link href={alert.href} className="underline-offset-2 hover:underline">
                  {alert.text}
                </Link>
              ) : (
                alert.text
              )}
            </li>
          ))}
        </ul>
      ) : null}

      <section className="mt-6 rounded-[var(--radius-md)] border border-[var(--line)] bg-[var(--surface)] p-5">
        <div className="flex flex-wrap items-baseline gap-x-4 gap-y-2">
          <span
            className={`rounded-[var(--radius-sm)] px-3 py-1 text-lg font-medium ${
              isOpen
                ? 'bg-[var(--success-tint)] text-[var(--success)]'
                : 'bg-[var(--surface-muted)] text-[var(--ink-muted)]'
            }`}
          >
            {isOpen ? 'Ouvert' : 'Fermé'}
          </span>
          <span className="text-lg">
            {status.today.slots.length > 0 ? formatHoursText(status.today.slots) : 'Fermé aujourd’hui'}
          </span>
          <span className="text-[var(--ink-muted)]">
            {formatNextChangeFr(
              status.nextChangeAt
                ? { kind: isOpen ? 'CLOSES' : 'OPENS', ...status.nextChangeAt }
                : null,
              today,
            ) || 'Aucune réouverture programmée'}
          </span>
        </div>
        <p className="mt-2 text-sm text-[var(--ink-muted)]">{formatDateFr(today)}</p>
      </section>

      <div className="mt-8 grid gap-8 lg:grid-cols-[1.2fr_1fr]">
        <section>
          <h2 className="text-lg">L’écran en ce moment</h2>
          <ScreenPreview className="mt-3" />
        </section>

        <section>
          <h2 className="text-lg">Appareil</h2>
          {device && health ? (
            <dl className="mt-3 space-y-2 text-sm">
              <Row label="Identifiant">{device.friendlyId}</Row>
              <Row label="Dernier contact">
                {device.lastSeenAt ? humaniseSeconds(secondsSince(device.lastSeenAt, now)) : 'jamais'}
              </Row>
              <Row label="Prochain réveil">
                {health.secondsUntilWake === null
                  ? 'inconnu'
                  : health.secondsUntilWake >= 0
                    ? humaniseSeconds(health.secondsUntilWake)
                    : 'attendu, en retard'}
              </Row>
              <Row label="Batterie">
                {health.batteryPercent === null
                  ? 'inconnue'
                  : `environ ${health.batteryPercent}%${device.percentCharged === null ? ' (estimée)' : ''}`}
              </Row>
              <Row label="Wi-Fi">
                {health.signal === null
                  ? 'inconnu'
                  : { good: 'bon', fair: 'moyen', poor: 'faible' }[health.signal]}
              </Row>
              <Row label="Firmware">{device.fwVersion ?? 'inconnu'}</Row>
            </dl>
          ) : (
            <p className="mt-3 text-sm text-[var(--ink-muted)]">Aucun écran appairé.</p>
          )}

          <p className="mt-4 rounded-[var(--radius-md)] bg-[var(--surface-muted)] px-3 py-2 text-sm text-[var(--ink-muted)]">
            L’écran fonctionne sur batterie et dort entre deux réveils&nbsp;: une modification
            n’apparaît qu’au réveil suivant. Rien ne peut lui être poussé.
          </p>
        </section>
      </div>

      <section className="mt-10">
        <h2 className="text-lg">Les sept prochains jours</h2>
        <ul className="mt-3 divide-y divide-[var(--line)] overflow-hidden rounded-[var(--radius-md)] border border-[var(--line)] bg-[var(--surface)]">
          {week.map((day, index) => (
            <li key={day.date} className="flex flex-wrap items-center gap-x-3 gap-y-1 px-4 py-2.5">
              <span className={`min-w-44 ${index === 0 ? 'font-medium' : ''}`}>
                {formatDateFr(day.date)}
                {index === 0 ? ' (aujourd’hui)' : ''}
              </span>
              <span className={day.isOpen ? '' : 'text-[var(--ink-muted)]'}>
                {day.slots.length > 0 ? formatHoursText(day.slots) : 'Fermé'}
              </span>
              {day.isException ? (
                <span className="rounded-[var(--radius-sm)] bg-[var(--accent-tint)] px-2 py-0.5 text-xs text-[var(--accent-ink)]">
                  {day.noteFr ?? 'exception'}
                </span>
              ) : null}
            </li>
          ))}
        </ul>
        <p className="mt-2 text-sm text-[var(--ink-muted)]">
          <Link href="/admin/exceptions" className="underline-offset-2 hover:underline">
            Modifier les horaires d’aujourd’hui
          </Link>
        </p>
      </section>

    </main>
  );
}

/** Negative, so `humaniseSeconds` phrases it as "il y a …". */
function secondsSince(moment: Date | null, now: Date): number {
  return moment ? Math.round((moment.getTime() - now.getTime()) / 1000) : 0;
}

function Row({ label, children }: { label: string; children: React.ReactNode }) {
  return (
    <div className="flex justify-between gap-4 border-b border-[var(--line)] pb-2">
      <dt className="text-[var(--ink-muted)]">{label}</dt>
      <dd className="text-right">{children}</dd>
    </div>
  );
}