calculateLocalAssetInfo.ts

import { ApiPromise, WsProvider } from '@polkadot/api';
import { xxhashAsU8a, blake2AsU8a } from '@polkadot/util-crypto';
import { u8aToHex, hexToU8a, numberToU8a } from '@polkadot/util';
import yargs from 'yargs';

const args = yargs.options({
  asset: { type: 'string', demandOption: true, alias: 'a' },
  network: { type: 'string', demandOption: false, alias: 'n' },
}).argv;

// Create Provider
let wsProvider;
if (args['network'] === 'moonbeam') {
  wsProvider = new WsProvider('wss://wss.api.moonbeam.network');
} else if (args['network'] === 'moonriver') {
  wsProvider = new WsProvider('wss://wss.api.moonriver.moonbeam.network');
} else if (args['network'] === 'moonbase') {
  wsProvider = new WsProvider('wss://wss.api.moonbase.moonbeam.network');
} else {
  console.error('Network not supported');
  process.exit();
}

const calculateStuff = (assetIdHex) => {
  let palletEncoder = new TextEncoder().encode('EVM');
  let palletHash = xxhashAsU8a(palletEncoder, 128);
  let storageEncoder = new TextEncoder().encode('AccountCodes');
  let storageHash = xxhashAsU8a(storageEncoder, 128);
  let assetAddress = new Uint8Array([
    ...hexToU8a('0xFFFFFFFE'),
    ...hexToU8a(assetIdHex),
  ]);
  let addressHash = blake2AsU8a(assetAddress, 128);

  let concatKey = new Uint8Array([
    ...palletHash,
    ...storageHash,
    ...addressHash,
    ...assetAddress,
  ]);

  console.log(`Storage Key ${u8aToHex(concatKey)}`);
  console.log(`Asset Address Precompile: ${u8aToHex(assetAddress)}`);
  console.log(`Asset ID is ${BigInt(assetIdHex).toString(10)}\n\n`);
};

const main = async () => {
  // Wait for Provider
  const api = await ApiPromise.create({
    provider: wsProvider,
    noInitWarn: true,
  });
  await api.isReady;

  const asset: any = api.createType('u128', JSON.parse(args['asset']));

  // For Legacy Assed ID we need to add 1 byte that is  4 x length of the original uint8
  const legacyAsset = new Uint8Array([
    ...numberToU8a(4 * asset.toU8a().length),
    ...asset.toU8a(),
  ]);

  const assetIdHex = u8aToHex(
    api.registry.hash(asset.toU8a()).slice(0, 16).reverse()
  );
  console.log(assetIdHex);
  const assetIdLegacyHex = u8aToHex(
    api.registry.hash(legacyAsset).slice(0, 16).reverse()
  );

  // Calculate Good Asset ID Stuff
  calculateStuff(assetIdHex);

  // Calculate Legacy Asset ID
  console.log(`Legacy Asset ID`);
  calculateStuff(assetIdLegacyHex);

  await api.disconnect();
};

main();