WORKSHOP_3_SOLUTIONS.md

Workshop 3 Solutions

Here you can find the solutions for the steps to implement in the third workshop. Try to implement the steps yourself first and only then check the solutions.

Rapid Gossip Sync

Future<void> _initialize(Mnemonic mnemonic) async {
    // 1. Add the following url as the Rapid Gossip Sync server url to source
    //  the network graph data from: https://rgs.mutinynet.com/snapshot/
    final builder = Builder()
        .setEntropyBip39Mnemonic(mnemonic: mnemonic)
        .setStorageDirPath(await _nodePath)
        .setNetwork(Network.signet)
        .setEsploraServer('https://mutinynet.ltbl.io/api')
        .setListeningAddresses(
          [
            const SocketAddress.hostname(addr: '0.0.0.0', port: 9735),
          ],
        )
        .setGossipSourceRgs('https://mutinynet.ltbl.io/snapshot');

    _node = await builder.build();

    await _node!.start();

    await _printRgsTimestamp();
    await _printLogs();
}

JIT channels with LSPS2

Set the LSPS2 Liquidity Source

Future<void> _initialize(Mnemonic mnemonic) async {
    // 2. Add the following LSP to be able to request LSPS2 JIT channels:
    //  Node Pubkey: 0371d6fd7d75de2d0372d03ea00e8bacdacb50c27d0eaea0a76a0622eff1f5ef2b
    //  Node Address: 44.219.111.31:39735
    //  Access token: JZWN9YLW
    final builder = Builder()
        .setEntropyBip39Mnemonic(mnemonic: mnemonic)
        .setStorageDirPath(await _nodePath)
        .setNetwork(Network.signet)
        .setEsploraServer('https://mutinynet.ltbl.io/api')
        .setListeningAddresses(
          [
            const SocketAddress.hostname(addr: '0.0.0.0', port: 9735),
          ],
        )
        .setGossipSourceRgs('https://mutinynet.ltbl.io/snapshot')
        .setLiquiditySourceLsps2(
          address: const SocketAddress.hostname(
            addr: '44.228.24.253',
            port: 9735,
          ),
          publicKey: const PublicKey(
            hexCode:
                '025804d4431ad05b06a1a1ee41f22fefeb8ce800b0be3a92ff3b9f594a263da34e',
          ),
          token: 'JZWN9YLW',
        );

    _node = await builder.build();

    await _node!.start();

    await _printRgsTimestamp();
    await _printLogs();
}

Check inbound liquidity

Future<int> get inboundLiquiditySat async {
    if (_node == null) {
      return 0;
    }

    // 3. Get the total inbound liquidity in satoshis by summing up the inbound
    //  capacity of all channels that are usable and return it in satoshis.
    final usableChannels = (await _node!.listChannels()).where(
      (channel) => channel.isUsable,
    );
    final inboundCapacityMsat = usableChannels.fold(
      0,
      (sum, channel) => sum + channel.inboundCapacityMsat,
    );

    return inboundCapacityMsat ~/ 1000;
}

Request JIT channels

@override
Future<(String?, String?)> generateInvoices({
    int? amountSat,
    int expirySecs = 3600 * 24, // Default to 1 day
    String description = 'BBE Workshop',
}) async {
    if (_node == null) {
        throw NoWalletException('A Lightning node has to be initialized first!');
    }

    Bolt11Invoice? bolt11;
    try {
      if (amountSat == null) {
          // 4. Change to receive via a JIT channel when no amount is specified
          bolt11 = await _node!.receiveVariableAmountPaymentViaJitChannel(
              expirySecs: expirySecs,
              description: description,
          );
      } else {
          // 5. Check the inbound liquidity and request a JIT channel if needed
          //  otherwise receive the payment as usual.
          if (await inboundLiquiditySat < amountSat) {
              bolt11 = await _node!.receivePaymentViaJitChannel(
                  amountMsat: amountSat * 1000,
                  expirySecs: expirySecs,
                  description: description,
              );
          } else {
              bolt11 = await _node!.receivePayment(
                  amountMsat: amountSat * 1000,
                  expirySecs: expirySecs,
                  description: description,
              );
          }
      }
    } catch (e) {
      final errorMessage = 'Failed to generate invoice: $e';
      print(errorMessage);
    }

    final bitcoinAddress = await _node!.newOnchainAddress();

    return (bitcoinAddress.s, bolt11 == null ? '' : bolt11.signedRawInvoice);
}