import { NextResponse } from "next/server";
import { verifyRegistrationResponse } from "@simplewebauthn/server";
import type { RegistrationResponseJSON } from "@simplewebauthn/server";
import { query } from "@/lib/db";
import { requireSession, UnauthorizedError } from "@/lib/auth/session";
import { origin, rpID } from "@/lib/auth/webauthn-config";
import { consumeChallenge } from "@/lib/auth/webauthn-challenges";
import { isSameOrigin } from "@/lib/origin";

export async function POST(request: Request) {
  if (!isSameOrigin(request)) {
    return NextResponse.json({ error: "Nicht erlaubt." }, { status: 403 });
  }
  try {
    const session = await requireSession();
    const body = (await request.json()) as {
      response: RegistrationResponseJSON;
      name?: string;
    };

    const challenge = extractChallengeFromClientData(body.response);
    const pending = await consumeChallenge(challenge, "registration");
    if (!pending || pending.userId !== session.user.id) {
      return NextResponse.json({ error: "challenge_expired" }, { status: 400 });
    }

    const verification = await verifyRegistrationResponse({
      response: body.response,
      expectedChallenge: challenge,
      expectedOrigin: origin(),
      expectedRPID: rpID(),
    });

    if (!verification.verified || !verification.registrationInfo) {
      return NextResponse.json({ error: "verification_failed" }, { status: 400 });
    }

    const { credential } = verification.registrationInfo;
    await query(
      `insert into passkey_credentials (user_id, credential_id, public_key, counter, transports, name)
       values ($1, $2, $3, $4, $5, $6)`,
      [
        session.user.id,
        credential.id,
        Buffer.from(credential.publicKey),
        credential.counter,
        credential.transports ?? [],
        body.name ?? null,
      ]
    );

    return NextResponse.json({ ok: true });
  } catch (err) {
    if (err instanceof UnauthorizedError) {
      return NextResponse.json({ error: "unauthorized" }, { status: 401 });
    }
    throw err;
  }
}

// clientDataJSON ist base64url-kodiertes JSON mit dem Feld "challenge" –
// darüber wird die zugehörige, serverseitig gespeicherte Challenge
// gefunden, ohne sie zusätzlich im Request-Body mitschicken zu müssen.
function extractChallengeFromClientData(response: RegistrationResponseJSON): string {
  const json = JSON.parse(
    Buffer.from(response.response.clientDataJSON, "base64url").toString("utf8")
  ) as { challenge: string };
  return json.challenge;
}