Bitbox lite

Lite version of Bitcoin.com's Bitbox JS library for building Bitcoin Cash apps in Flutter. Integrated to Bitcoin.com's REST API. Works with mainnet and testnet.

Getting Started

1) Depend on it

dependencies:
  bitbox:
    git:
      url: https://github.com/RomitRadical/bitbox-flutter
      ref: master

2) Import it

// There's a good chance your own project will use similar names as some of the
// classes in this library. A simple way to create some order is to import the
// library with Bitbox prefix:
import 'package:bitbox/bitbox.dart' as bitbox;

2) Use it

// set this to true to use testnet
final testnet = true;

// After running the code for the first time, depositing an amount to the address
// displayed in the console, and waiting for confirmation, paste the generated
// mnemonic here, so the code continues below with address withdrawal
String mnemonic = "";

if (mnemonic == "") {
  // generate 12-word (128bit) mnemonic
  mnemonic = Bitbox.Mnemonic.generate();

  print(mnemonic);
}

// generate a seed from mnemonic
final seed = Bitbox.Mnemonic.toSeed(mnemonic);

// create an instance of Bitbox.HDNode for mainnet
final masterNode = Bitbox.HDNode.fromSeed(seed, testnet);

// This format is compatible with Bitcoin.com wallet.
// Other wallets use Change to m/44'/145'/0'/0
final accountDerivationPath = "m/44'/0'/0'/0";

// create an account node using the provided derivation path
final accountNode = masterNode.derivePath(accountDerivationPath);

// get account's extended private key
final accountXPriv = accountNode.toXPriv();

// create a Bitbox.HDNode instance of the first child in this account
final childNode = accountNode.derive(0);

// get an address of the child
final address = childNode.toCashAddress();

// if you are using testnet, set the appropriate rest api url before making any API
// calls (like getting address or transaction details or broadcasting a transaction
if (testnet) {
  Bitbox.Bitbox.setRestUrl(restUrl: Bitbox.Bitbox.trestUrl);
}

// get address details
final addressDetails = await Bitbox.Address.details(address);

print(addressDetails);

// If there is a confirmed balance, attempt to withdraw it
if (addressDetails["balance"] > 0) {
  final builder = Bitbox.Bitbox.transactionBuilder(testnet: testnet);

  // retrieve address' utxos from the rest api
  final utxos = await Bitbox.Address.utxo(address) as List<Bitbox.Utxo>;

  // placeholder for input signatures
  final signatures = <Map>[];

  // placeholder for total input balance
  int totalBalance = 0;

  // iterate through the list of address utxos and use them as inputs for the
  // withdrawal transaction
  utxos.forEach((Bitbox.Utxo utxo) {
    // add the utxo as an input for the transaction
    builder.addInput(utxo.txid, utxo.vout);

    // add a signature to the list to be used later
    signatures.add({
      "vin": signatures.length,
      "key_pair": childNode.keyPair,
      "original_amount": utxo.satoshis
    });

    totalBalance += utxo.satoshis;
  });

  // set an address to send the remaining balance to
  final outputAddress = "";

  // if there is an unspent balance, create a spending transaction
  if (totalBalance > 0 && outputAddress != "") {
    // calculate the fee based on number of inputs and one expected output
    final fee = Bitbox.BitcoinCash.getByteCount(signatures.length, 1);

    // calculate how much balance will be left over to spend after the fee
    final sendAmount = totalBalance - fee;

    // add the output based on the address provided in the testing data
    builder.addOutput(outputAddress, sendAmount);

    // sign all inputs
    signatures.forEach((signature) {
      builder.sign(signature["vin"], signature["key_pair"],
	    signature["original_amount"]);
    });

    // build the transaction
    final tx = builder.build();

    // broadcast the transaction
    final txid = await Bitbox.RawTransactions.sendRawTransaction(tx.toHex());

    // Yatta!
    print("Transaction broadcasted: $txid");
  } else if (totalBalance > 0) {
    print("Enter an output address to test withdrawal transaction");
  }
}

For further documentation, refer to apidoc of this repository

Testing

There are some unit tests in test/bitbox_test.dart. They use data generated from the original Bitbox for JS and compare them with the output of this library. The following is tested for both testnet and mainnet:

Generating the master node from mnemonic and comparing both its XPub and XPriv
Generating an account node and comparing XPub and XPriv
Generating 10 test childs and comparing their private keys and addresses
Conversion of cashAddr format to legacy and vice versa
Fetching address details for the rest API
Fetching utxos for addresses with balance
Building a transaction spending the deposited balance and comparing its hash with Bitbox JS output
Optionally broadcasting the transaction and

To run the test:

Copy create_test_data.js to a separate directory and download the original Bitbox JS into the directory
Generate the testing data by runing create_test_data.js with your local nodeJS engine
Update bitbox_test.dart with the path to the generated test_data.json file
Run bitbox_test.dart Optionally between step 1) and 2), send some balance to either testnet or mainnet addresses (or both), wait for confirmations and run create_test_data.js again to update the data and generate testing transactions

Acknowledgments

This is a port of the original JS-based Bitbox library by Gabriel Cardona and Bitcoin.com, so first of all huge thanks to Gabriel and the whole Bitcoin.com team for doing so much for the BCH ecosystem.

Also I either re-used a lot of code originally wrote for Bitcoin or called some libraries (bip39 and bip32) by anicdh, so Thanks big time to him. Without that it would take me many more weeks!