stellarService.js

require("dotenv").config();
const { Horizon, Asset, StrKey } = require("stellar-sdk");

// Shared Horizon server instance
const server = new Horizon.Server(
  process.env.HORIZON_URL || "https://horizon-testnet.stellar.org",
);

/**
 * Returns a Stellar Asset object.
 * Returns Asset.native() if code is 'XLM', otherwise returns a non-native Asset.
 *
 * @param {string} code - Asset code (e.g. 'NOVA', 'XLM')
 * @param {string} [issuer] - Asset issuer public key (optional for XLM)
 * @returns {Asset}
 */
function getAsset(code, issuer) {
  if (code === "XLM" || code === "native") {
    return Asset.native();
  }
  const asset = new Asset(code, issuer);
  return asset;
}
// NOVA asset definition — issued by the Issuer Account
const NOVA = getAsset("NOVA", process.env.ISSUER_PUBLIC);

/**
 * Validates that a string is a valid Stellar public key.
 * Must be a 56-character G-prefixed Ed25519 public key.
 * Requirements: 5.1
 *
 * @param {string} address
 * @returns {boolean}
 */
function isValidStellarAddress(address) {
  if (typeof address !== "string") return false;
  try {
    return StrKey.isValidEd25519PublicKey(address);
  } catch {
    return false;
  }
}

/**
 * Queries Horizon for the account's current NOVA token balance.
 * Returns '0' if the account has no trustline for NOVA.
 * Requirements: 6.1, 8.3
 *
 * @param {string} walletAddress - Stellar public key
 * @returns {Promise<string>} NOVA balance as a string (e.g. "100.0000000")
 */
async function getNOVABalance(walletAddress) {
  try {
    const account = await server.loadAccount(walletAddress);
    const novaBalance = account.balances.find(
      (b) =>
        b.asset_type !== "native" &&
        b.asset_code === "NOVA" &&
        b.asset_issuer === process.env.ISSUER_PUBLIC,
    );
    return novaBalance ? novaBalance.balance : "0";
  } catch (err) {
    if (
      err.response?.status === 404 ||
      err.message?.toLowerCase().includes("not found")
    ) {
      return "0";
    }
    throw err;
  }
}

module.exports = {
  server,
  NOVA,
  isValidStellarAddress,
  getNOVABalance,
  getAsset,
};