'use client';

import api from '@/lib/api';

/**
 * Client-side "Login as user" (impersonation) helpers.
 *
 * The admin's own tokens are stashed under `admin*` keys while the active
 * `accessToken`/`refreshToken` are swapped for the impersonation tokens, so the
 * whole app (and the axios interceptor) transparently acts as the target user.
 * Both start and stop are recorded server-side in the audit log.
 */

const IMP_KEY = 'impersonation';

export interface ImpersonationInfo {
  targetUserId: string;
  targetName: string;
}

export function getImpersonation(): ImpersonationInfo | null {
  if (typeof window === 'undefined') return null;
  try {
    const raw = localStorage.getItem(IMP_KEY);
    return raw ? (JSON.parse(raw) as ImpersonationInfo) : null;
  } catch {
    return null;
  }
}

export function isImpersonating(): boolean {
  return getImpersonation() !== null;
}

/** Begin impersonating a user. Caller should hard-reload afterwards. */
export async function startImpersonation(targetUserId: string): Promise<ImpersonationInfo> {
  const { data } = await api.post(`/admin/users/${targetUserId}/impersonate`);
  // Stash the admin session so we can return to it later.
  localStorage.setItem('adminAccessToken', localStorage.getItem('accessToken') ?? '');
  localStorage.setItem('adminRefreshToken', localStorage.getItem('refreshToken') ?? '');
  const info: ImpersonationInfo = {
    targetUserId,
    targetName: `${data.user?.firstName ?? ''} ${data.user?.lastName ?? ''}`.trim(),
  };
  localStorage.setItem(IMP_KEY, JSON.stringify(info));
  // Swap in the impersonation tokens.
  localStorage.setItem('accessToken', data.accessToken);
  localStorage.setItem('refreshToken', data.refreshToken);
  return info;
}

/** End impersonation, restoring the admin session. Caller should hard-reload. */
export async function stopImpersonation(): Promise<string | null> {
  const info = getImpersonation();
  const adminAccess = localStorage.getItem('adminAccessToken');
  const adminRefresh = localStorage.getItem('adminRefreshToken');

  // Restore the admin tokens first so the stop call is authorized as the admin.
  if (adminAccess) localStorage.setItem('accessToken', adminAccess);
  if (adminRefresh) localStorage.setItem('refreshToken', adminRefresh);
  localStorage.removeItem('adminAccessToken');
  localStorage.removeItem('adminRefreshToken');
  localStorage.removeItem(IMP_KEY);

  if (info?.targetUserId) {
    try {
      await api.post(`/admin/users/${info.targetUserId}/impersonation/stop`);
    } catch {
      // Best-effort audit; never block returning to the admin session.
    }
  }
  return info?.targetUserId ?? null;
}

/** Clear any impersonation artefacts (used on full logout). */
export function clearImpersonation(): void {
  if (typeof window === 'undefined') return;
  localStorage.removeItem('adminAccessToken');
  localStorage.removeItem('adminRefreshToken');
  localStorage.removeItem(IMP_KEY);
}