import { type NextRequest } from 'next/server';
import { randomBytes } from 'node:crypto';
import { createSupabaseServerClient } from '@/lib/supabase/server';
import { getSupabaseAdmin } from '@/lib/supabase/admin';
import { jsonNoStore } from '@/lib/admin/response';
import { validateSubdomain } from '@/lib/validation';
import { setTunnelActive } from '@/lib/redis';
import { normalizeUserCode } from '@/lib/device';

export const runtime = 'nodejs';
export const dynamic = 'force-dynamic';

type ApproveBody = { user_code?: unknown; subdomain?: unknown };

type Pairing = {
  id: number;
  status: string;
  expires_at: string;
};

/**
 * Approve a device pairing (AUTHENTICATED + AAL2). The signed-in user binds a
 * pending user_code to their account and chooses/reuses a subdomain.
 */
export async function POST(req: NextRequest) {
  const supabase = createSupabaseServerClient();
  const {
    data: { user },
  } = await supabase.auth.getUser();
  if (!user) return jsonNoStore({ error: 'unauthorized' }, { status: 401 });
  const { data: aal } = await supabase.auth.mfa.getAuthenticatorAssuranceLevel();
  if (aal?.currentLevel !== 'aal2') {
    return jsonNoStore({ error: 'aal2_required' }, { status: 403 });
  }

  let body: ApproveBody;
  try {
    body = (await req.json()) as ApproveBody;
  } catch {
    return jsonNoStore({ error: 'invalid json' }, { status: 400 });
  }

  const userCode = normalizeUserCode(
    typeof body.user_code === 'string' ? body.user_code : '',
  );
  if (!userCode) {
    return jsonNoStore({ error: 'invalid_user_code' }, { status: 400 });
  }

  const admin = getSupabaseAdmin();

  const { data: pairing, error: pairingErr } = await admin
    .from('device_pairings')
    .select('id, status, expires_at')
    .eq('user_code', userCode)
    .eq('status', 'pending')
    .maybeSingle<Pairing>();
  if (pairingErr) {
    return jsonNoStore({ error: 'failed' }, { status: 500 });
  }
  if (!pairing) {
    return jsonNoStore({ error: 'invalid_user_code' }, { status: 400 });
  }
  if (new Date(pairing.expires_at).getTime() < Date.now()) {
    await admin
      .from('device_pairings')
      .update({ status: 'expired' })
      .eq('id', pairing.id);
    return jsonNoStore({ error: 'expired' }, { status: 400 });
  }

  let subdomain: string;

  if (body.subdomain !== undefined) {
    const v = validateSubdomain(body.subdomain);
    if (!v.ok) {
      return jsonNoStore({ error: v.error }, { status: 400 });
    }
    subdomain = v.value;

    // Reject if the subdomain is already owned by another user.
    const { data: existing, error: existingErr } = await admin
      .from('tunnels')
      .select('user_id')
      .eq('subdomain', subdomain)
      .maybeSingle<{ user_id: string }>();
    if (existingErr) {
      return jsonNoStore({ error: 'failed' }, { status: 500 });
    }
    if (existing && existing.user_id !== user.id) {
      return jsonNoStore({ error: 'subdomain taken' }, { status: 409 });
    }

    const token = randomBytes(32).toString('hex');
    const { error: upsertErr } = await admin
      .from('tunnels')
      .upsert(
        { user_id: user.id, subdomain, token, is_active: true },
        { onConflict: 'user_id' },
      )
      .select('subdomain')
      .single();
    if (upsertErr) {
      if ((upsertErr as { code?: string }).code === '23505') {
        return jsonNoStore({ error: 'subdomain taken' }, { status: 409 });
      }
      return jsonNoStore({ error: 'failed' }, { status: 500 });
    }

    await setTunnelActive(subdomain, true);
  } else {
    // Reuse the user's existing subdomain without rotating the frp token.
    const { data: tunnel, error: tunnelErr } = await admin
      .from('tunnels')
      .select('subdomain')
      .eq('user_id', user.id)
      .maybeSingle<{ subdomain: string }>();
    if (tunnelErr) {
      return jsonNoStore({ error: 'failed' }, { status: 500 });
    }
    if (!tunnel) {
      return jsonNoStore({ error: 'subdomain_required' }, { status: 400 });
    }
    subdomain = tunnel.subdomain;
  }

  const { error: updateErr } = await admin
    .from('device_pairings')
    .update({
      user_id: user.id,
      subdomain,
      status: 'approved',
      approved_at: new Date().toISOString(),
    })
    .eq('id', pairing.id);
  if (updateErr) {
    return jsonNoStore({ error: 'failed' }, { status: 500 });
  }

  return jsonNoStore({ ok: true, subdomain });
}