gbn_ln_bot/src/api/routes/setup.ts

import type { FastifyInstance } from "fastify";
import { validateInitData, AuthError } from "../auth";
import { checkPinRateLimit, recordPinFailure, recordPinSuccess, RateLimitError } from "../ratelimit";
import { findUser, createUser } from "../../db/users";
import { generateMnemonic, deriveSparkAddress } from "../../payments/wallet";
import { encryptMnemonic } from "../../payments/crypto";
import { publishToRegistry } from "../../payments/registry";

const MIN_PIN_LENGTH = 6;

interface SetupBody {
  pin: string;
}

export async function setupRoutes(app: FastifyInstance): Promise<void> {
  /**
   * POST /api/setup
   *
   * Creates a new wallet for the authenticated Telegram user.
   * Returns the seed words once in the response — the Mini App displays and
   * discards them. Nothing is stored in Telegram chat history.
   */
  app.post<{ Body: SetupBody }>("/api/setup", async (req, reply) => {
    const initData = req.headers["x-init-data"] as string | undefined;
    if (!initData) return reply.status(401).send({ error: "Missing X-Init-Data header" });

    let userId: number;
    let username: string | undefined;
    try {
      const validated = validateInitData(initData);
      userId = validated.user.id;
      username = validated.user.username;
    } catch (err) {
      return reply.status(401).send({ error: err instanceof AuthError ? err.message : "Unauthorized" });
    }

    if (findUser(userId)) {
      return reply.status(409).send({ error: "Wallet already exists." });
    }

    const { pin } = req.body ?? {};
    if (!pin || typeof pin !== "string") {
      return reply.status(400).send({ error: "pin is required" });
    }
    if (pin.length < MIN_PIN_LENGTH) {
      return reply.status(400).send({ error: `PIN must be at least ${MIN_PIN_LENGTH} characters.` });
    }

    try {
      checkPinRateLimit(userId);
    } catch (err) {
      if (err instanceof RateLimitError) return reply.status(429).send({ error: err.message });
      throw err;
    }

    // Generate and encrypt — PIN is never stored, only the encrypted blob
    const mnemonic = generateMnemonic();
    const sparkAddress = await deriveSparkAddress(mnemonic);
    const encryptedMnemonic = encryptMnemonic(mnemonic, pin);

    createUser(userId, username ?? null, encryptedMnemonic, sparkAddress);
    recordPinSuccess(userId);

    await publishToRegistry(userId, sparkAddress).catch(() => null);

    // Return seed words directly — this is an authenticated HTTPS call,
    // nothing is written to Telegram's servers.
    return {
      words: mnemonic.split(" "),
      sparkAddress,
    };
  });
}