'use client';
import { useCallback, useEffect, useState, type FormEvent } from 'react';
import { useParams } from 'next/navigation';
import Link from 'next/link';
import { api, apiUpload, errMsg } from '@/lib/api';
import { useSession } from '@/lib/session';
import { Alert, Field, TicketStatusBadge, TICKET_PRIORITY, fmt } from '@/components/ui';

const MAX_FILES = 5;
const ALLOWED = 'image/png,image/jpeg,image/gif,image/webp,application/pdf';
interface Attachment { id: string; filename: string; contentType: string; sizeBytes: number }
function AttachmentList({ ticketId, atts }: { ticketId: string; atts: Attachment[] }) {
  if (atts.length === 0) return null;
  return (<div className="row" style={{ marginTop: 8, flexWrap: 'wrap', gap: 8 }}>
    {atts.map((a) => { const href = `/api/tickets/${ticketId}/attachments/${a.id}`; const kb = Math.max(1, Math.round(a.sizeBytes / 1024));
      return a.contentType.startsWith('image/')
        ? <a key={a.id} href={href} target="_blank" rel="noreferrer" title={`${a.filename} (${kb} KB)`}><img src={href} alt={a.filename} style={{ maxWidth: 160, maxHeight: 120, borderRadius: 6, border: '1px solid var(--border)', display: 'block' }} /></a>
        : <a key={a.id} className="btn small" href={href} target="_blank" rel="noreferrer">📄 {a.filename} <span className="muted small">({kb} KB)</span></a>; })}
  </div>);
}
interface Msg { id: string; authorId: string; authorName: string; authorKind: 'customer' | 'staff'; body: string; internalNote: boolean; createdAt: string; attachments: Attachment[] }
interface Detail { id: string; number: string; orgId: string; orgName: string; subject: string; status: string; priority: string; assignedTo: string | null; assignedName: string | null; resourceId: string | null; resourceName: string | null; resourceType: string | null; domainRecordId: string | null; domain: string | null; messages: Msg[]; canWrite: boolean }
interface StaffUser { id: string; name: string; staffRole: string | null }
const STATUS_OPTIONS = { open: 'Offen', pending_customer: 'Wartet auf Kunde', pending_staff: 'Wartet auf Personal', resolved: 'Gelöst', closed: 'Geschlossen' };

export default function TicketDetail() {
  const { id } = useParams<{ id: string }>(); const { can } = useSession(); const staff = can('tickets.read'); const write = can('tickets.write');
  const [t, setT] = useState<Detail | null>(null); const [err, setErr] = useState(''); const [ok, setOk] = useState(''); const [busy, setBusy] = useState(false);
  const [staffUsers, setStaffUsers] = useState<StaffUser[]>([]);
  const load = useCallback(() => api<Detail>('GET', `/tickets/${id}`).then(setT).catch((e) => setErr(errMsg(e))), [id]);
  useEffect(() => { void load(); }, [load]);
  useEffect(() => { if (write) api<StaffUser[]>('GET', '/admin/users').then((l) => setStaffUsers(l.filter((u) => !!u.staffRole))).catch(() => undefined); }, [write]);

  async function send(e: FormEvent<HTMLFormElement>) {
    e.preventDefault(); setErr(''); setBusy(true); const f = e.currentTarget; const fd = new FormData(f);
    const body = String(fd.get('body') ?? ''); const internal = fd.get('internal') === 'on';
    const files = (fd.getAll('files') as File[]).filter((x) => x instanceof File && x.size > 0);
    try {
      const { messageId } = await api<{ messageId: string }>('POST', `/tickets/${id}/messages`, { body, internalNote: internal });
      f.reset();
      if (files.length > 0) { try { await apiUpload(`/tickets/${id}/messages/${messageId}/attachments`, files); } catch (x) { setErr(`Nachricht gesendet, aber Anhang fehlgeschlagen: ${errMsg(x)}`); } }
      void load();
    } catch (x) { setErr(errMsg(x)); } finally { setBusy(false); }
  }
  async function patch(body: object, msg?: string) { setErr(''); setOk(''); try { await api('PATCH', `/tickets/${id}`, body); if (msg) setOk(msg); void load(); } catch (x) { setErr(errMsg(x)); } }
  async function close() { setErr(''); try { await api('POST', `/tickets/${id}/close`); void load(); } catch (x) { setErr(errMsg(x)); } }

  if (!t) return err ? <Alert kind="err">{err}</Alert> : <p className="muted" role="status">Wird geladen …</p>;
  const canClose = t.status !== 'closed';
  return (<>
    <div className="row between"><h1>{t.number}: {t.subject}</h1><Link className="btn" href="/tickets">← Tickets</Link></div>
    <p className="muted small">{staff && <>{t.orgName} · </>}<TicketStatusBadge value={t.status} /> · Priorität: {TICKET_PRIORITY[t.priority]}{t.assignedName && <> · zugewiesen an {t.assignedName}</>}</p>
    {(t.domain || t.resourceName) && <p className="muted small">Betrifft: {t.resourceId ? <Link href={`/ressourcen/${t.resourceId}`}>{t.resourceName}</Link> : staff ? <Link href={`/admin/domains?q=${encodeURIComponent(t.domain!)}`}>{t.domain}</Link> : t.domain}</p>}
    {err && <Alert kind="err">{err}</Alert>}{ok && <Alert kind="ok">{ok}</Alert>}
    {write && <div className="card"><div className="cols">
      <Field id="status" label="Status"><select id="status" value={t.status} onChange={(e) => patch({ status: e.target.value })}>{Object.entries(STATUS_OPTIONS).map(([k, v]) => <option key={k} value={k}>{v}</option>)}</select></Field>
      <Field id="priority" label="Priorität"><select id="priority" value={t.priority} onChange={(e) => patch({ priority: e.target.value })}>{Object.entries(TICKET_PRIORITY).map(([k, v]) => <option key={k} value={k}>{v}</option>)}</select></Field>
      <Field id="assignee" label="Zugewiesen an"><select id="assignee" value={t.assignedTo ?? ''} onChange={(e) => patch({ assignedTo: e.target.value || null })}><option value="">Niemand</option>{staffUsers.map((u) => <option key={u.id} value={u.id}>{u.name}</option>)}</select></Field>
    </div></div>}
    <div className="card">
      {t.messages.map((m) => (<div key={m.id} style={{ padding: '12px 0', borderBottom: '1px solid var(--border)' }}>
        <div className="row between small muted"><span>{m.authorName} ({m.authorKind === 'staff' ? 'Personal' : 'Kunde'}){m.internalNote && <> · <span className="badge warn">nur intern</span></>}</span><span>{fmt(m.createdAt)}</span></div>
        <p style={{ whiteSpace: 'pre-wrap', margin: '4px 0 0' }}>{m.body}</p>
        <AttachmentList ticketId={t.id} atts={m.attachments} /></div>))}
    </div>
    {t.status === 'closed' ? <p className="muted">Dieses Ticket ist geschlossen. Für neue Anliegen bitte ein neues Ticket eröffnen.</p> : t.canWrite && <form className="card" onSubmit={send}>
      <Field id="body" label="Antwort"><textarea id="body" name="body" required rows={4} style={{ width: '100%' }} /></Field>
      <Field id="files" label="Anhänge (optional)" hint={`Bilder oder PDF, höchstens ${MAX_FILES} Dateien, je 15 MB.`}><input id="files" name="files" type="file" accept={ALLOWED} multiple /></Field>
      {staff && <label className="row small" style={{ marginBottom: 12 }}><input type="checkbox" name="internal" style={{ width: 20, minHeight: 20 }} /> Nur intern (für den Kunden nicht sichtbar)</label>}
      <div className="row"><button className="btn primary" type="submit" disabled={busy}>Absenden</button>{!staff && canClose && <button className="btn" type="button" onClick={close}>Als erledigt schließen</button>}</div>
    </form>}
  </>);
}