Wallet Integration

import { generateMnemonic, mnemonicToSeedSync, validateMnemonic } from 'bip39';
import { HDKey } from '@scure/bip32';
import { keccak_256 } from '@noble/hashes/sha3';
import { secp256k1 } from '@noble/curves/secp256k1';

const ETH_PATH = "m/44'/60'/0'/0/0";

export function deriveAccount(mnemonic: string) {
  const seed = mnemonicToSeedSync(mnemonic.trim());
  const node = HDKey.fromMasterSeed(Uint8Array.from(seed)).derive(ETH_PATH);
  if (!node.privateKey) throw new Error('derivation produced no private key');

  const privateKey = Uint8Array.from(node.privateKey);
  const publicKey = secp256k1.getPublicKey(privateKey, false); // uncompressed, 65 bytes
  const hashed = keccak_256(publicKey.slice(1));               // drop 0x04
  const address = '0x' + Buffer.from(hashed.slice(-20)).toString('hex');

  return { address, privateKey };
}

const mnemonicKey = (userId: string) => `yc_wallet_mnemonic__${userId}`;
const addressKey  = (userId: string) => `yc_wallet_address__${userId}`;

await EncryptedStorage.setItem(mnemonicKey(userId), normalizedPhrase);
await EncryptedStorage.setItem(addressKey(userId), address);

rlp([nonce, gasPrice, gasLimit, to, value, data, chainId, 0, 0])

rlp([nonce, gasPrice, gasLimit, to, value, data, v, r, s])

export function signTransaction(tx: UnsignedTx, privateKey: Uint8Array): string {
  const fields = [
    toMinimalBytes(tx.nonce),
    toMinimalBytes(tx.gasPrice),
    toMinimalBytes(tx.gasLimit),
    tx.to ? hexToBytes(tx.to) : new Uint8Array(0),
    toMinimalBytes(tx.value ?? 0),
    tx.data ? hexToBytes(tx.data) : new Uint8Array(0),
  ];

  const signingPayload = rlpEncode([...fields, toMinimalBytes(tx.chainId), new Uint8Array(0), new Uint8Array(0)]);
  const signature = secp256k1.sign(keccak_256(signingPayload), privateKey, { prehash: false });

  const v = BigInt(signature.recovery) + BigInt(tx.chainId) * 2n + 35n;
  return bytesToHex(rlpEncode([...fields, toMinimalBytes(v), toMinimalBytes(signature.r), toMinimalBytes(signature.s)]));
}

// 1. approve the converter to move the user's YCR
approve(converter, amount)                   // 0x095ea7b3

// 2. quote, then apply slippage tolerance (the app uses 95%)
quoteYCRForYCE(ycrIn)                        // 0xa41878f3
const minOut = (quoted * 95n) / 100n;

// 3. swap, signed by the user
swapYCRForYCE(ycrIn, minOut)                 // 0xb0c7c4f2