stack_wallet/lib/wallets/wallet/wallet_mixin_interfaces/spark_interface.dart

import 'dart:convert';

import 'package:bitcoindart/bitcoindart.dart' as btc;
import 'package:bitcoindart/src/utils/script.dart' as bscript;
import 'package:flutter/foundation.dart';
import 'package:flutter_libsparkmobile/flutter_libsparkmobile.dart';
import 'package:isar/isar.dart';
import 'package:stackwallet/models/balance.dart';
import 'package:stackwallet/models/isar/models/blockchain_data/address.dart';
import 'package:stackwallet/utilities/amount/amount.dart';
import 'package:stackwallet/utilities/extensions/extensions.dart';
import 'package:stackwallet/utilities/logger.dart';
import 'package:stackwallet/wallets/crypto_currency/crypto_currency.dart';
import 'package:stackwallet/wallets/isar/models/spark_coin.dart';
import 'package:stackwallet/wallets/models/tx_data.dart';
import 'package:stackwallet/wallets/wallet/intermediate/bip39_hd_wallet.dart';
import 'package:stackwallet/wallets/wallet/wallet_mixin_interfaces/electrumx_interface.dart';

const kDefaultSparkIndex = 1;

mixin SparkInterface on Bip39HDWallet, ElectrumXInterface {
  static bool validateSparkAddress({
    required String address,
    required bool isTestNet,
  }) =>
      LibSpark.validateAddress(address: address, isTestNet: isTestNet);

  @override
  Future<void> init() async {
    Address? address = await getCurrentReceivingSparkAddress();
    if (address == null) {
      address = await generateNextSparkAddress();
      await mainDB.putAddress(address);
    } // TODO add other address types to wallet info?

    // await info.updateReceivingAddress(
    //   newAddress: address.value,
    //   isar: mainDB.isar,
    // );

    await super.init();
  }

  @override
  Future<List<Address>> fetchAddressesForElectrumXScan() async {
    final allAddresses = await mainDB
        .getAddresses(walletId)
        .filter()
        .not()
        .group(
          (q) => q
              .typeEqualTo(AddressType.spark)
              .or()
              .typeEqualTo(AddressType.nonWallet)
              .or()
              .subTypeEqualTo(AddressSubType.nonWallet),
        )
        .findAll();
    return allAddresses;
  }

  Future<Address?> getCurrentReceivingSparkAddress() async {
    return await mainDB.isar.addresses
        .where()
        .walletIdEqualTo(walletId)
        .filter()
        .typeEqualTo(AddressType.spark)
        .sortByDerivationIndexDesc()
        .findFirst();
  }

  Future<Address> generateNextSparkAddress() async {
    final highestStoredDiversifier =
        (await getCurrentReceivingSparkAddress())?.derivationIndex;

    // default to starting at 1 if none found
    final int diversifier = (highestStoredDiversifier ?? 0) + 1;

    final root = await getRootHDNode();
    final String derivationPath;
    if (cryptoCurrency.network == CryptoCurrencyNetwork.test) {
      derivationPath = "$kSparkBaseDerivationPathTestnet$kDefaultSparkIndex";
    } else {
      derivationPath = "$kSparkBaseDerivationPath$kDefaultSparkIndex";
    }
    final keys = root.derivePath(derivationPath);

    final String addressString = await LibSpark.getAddress(
      privateKey: keys.privateKey.data,
      index: kDefaultSparkIndex,
      diversifier: diversifier,
      isTestNet: cryptoCurrency.network == CryptoCurrencyNetwork.test,
    );

    return Address(
      walletId: walletId,
      value: addressString,
      publicKey: keys.publicKey.data,
      derivationIndex: diversifier,
      derivationPath: DerivationPath()..value = derivationPath,
      type: AddressType.spark,
      subType: AddressSubType.receiving,
    );
  }

  Future<Amount> estimateFeeForSpark(Amount amount) async {
    throw UnimplementedError();
  }

  /// Spark to Spark/Transparent (spend) creation
  Future<TxData> prepareSendSpark({
    required TxData txData,
  }) async {
    final coins = await mainDB.isar.sparkCoins
        .where()
        .walletIdEqualToAnyLTagHash(walletId)
        .filter()
        .isUsedEqualTo(false)
        .findAll();

    final serializedCoins =
        coins.map((e) => (e.serializedCoinB64!, e.contextB64!)).toList();

    final currentId = await electrumXClient.getSparkLatestCoinId();
    final List<Map<String, dynamic>> setMaps = [];
    // for (int i = 0; i <= currentId; i++) {
    for (int i = currentId; i <= currentId; i++) {
      final set = await electrumXCachedClient.getSparkAnonymitySet(
        groupId: i.toString(),
        coin: info.coin,
      );
      set["coinGroupID"] = i;
      setMaps.add(set);
    }

    final allAnonymitySets = setMaps
        .map((e) => (
              setId: e["coinGroupID"] as int,
              setHash: e["setHash"] as String,
              set: (e["coins"] as List)
                  .map((e) => (
                        serializedCoin: e[0] as String,
                        txHash: e[1] as String,
                      ))
                  .toList(),
            ))
        .toList();

    // https://docs.google.com/document/d/1RG52GoYTZDvKlZz_3G4sQu-PpT6JWSZGHLNswWcrE3o/edit
    // To generate  a spark spend we need to call createSparkSpendTransaction,
    // first unlock the wallet and generate all 3 spark keys,

    final root = await getRootHDNode();
    final String derivationPath;
    if (cryptoCurrency.network == CryptoCurrencyNetwork.test) {
      derivationPath = "$kSparkBaseDerivationPathTestnet$kDefaultSparkIndex";
    } else {
      derivationPath = "$kSparkBaseDerivationPath$kDefaultSparkIndex";
    }
    final privateKey = root.derivePath(derivationPath).privateKey.data;
    //
    // recipients is a list of pairs of amounts and bools, this is for transparent
    // outputs, first how much to send and second, subtractFeeFromAmount argument
    // for each receiver.
    //
    // privateRecipients is again the list of pairs, first the receiver data
    // which has following members, Address which is any spark address,
    // amount (v) how much we want to send, and memo which can be any string
    // with 32 length (any string we want to send to receiver), and the second
    // subtractFeeFromAmount,
    //
    // coins is the list of all our available spark coins
    //
    // cover_set_data_all is the list of all anonymity sets,
    //
    // idAndBlockHashes_all is the list of block hashes for each anonymity set
    //
    // txHashSig is the transaction hash only without spark data, tx version,
    // type, transparent outputs and everything else should be set before generating it.
    //
    // fee is a output data
    //
    // serializedSpend is a output data, byte array with spark spend, we need
    // to put it into vExtraPayload (this naming can be different in your codebase)
    //
    // outputScripts is a output data, it is a list of scripts, which we need
    // to put in separate tx outputs, and keep the order,

    // Amount vOut = Amount(
    //     rawValue: BigInt.zero, fractionDigits: cryptoCurrency.fractionDigits);
    // Amount mintVOut = Amount(
    //     rawValue: BigInt.zero, fractionDigits: cryptoCurrency.fractionDigits);
    // int recipientsToSubtractFee = 0;
    //
    // for (int i = 0; i < (txData.recipients?.length ?? 0); i++) {
    //   vOut += txData.recipients![i].amount;
    // }
    //
    // if (vOut.raw > BigInt.from(SPARK_VALUE_SPEND_LIMIT_PER_TRANSACTION)) {
    //   throw Exception(
    //     "Spend to transparent address limit exceeded (10,000 Firo per transaction).",
    //   );
    // }
    //
    // for (int i = 0; i < (txData.sparkRecipients?.length ?? 0); i++) {
    //   mintVOut += txData.sparkRecipients![i].amount;
    //   if (txData.sparkRecipients![i].subtractFeeFromAmount) {
    //     recipientsToSubtractFee++;
    //   }
    // }
    //
    // int fee;

    final txb = btc.TransactionBuilder(
      network: btc.NetworkType(
        messagePrefix: cryptoCurrency.networkParams.messagePrefix,
        bech32: cryptoCurrency.networkParams.bech32Hrp,
        bip32: btc.Bip32Type(
          public: cryptoCurrency.networkParams.pubHDPrefix,
          private: cryptoCurrency.networkParams.privHDPrefix,
        ),
        pubKeyHash: cryptoCurrency.networkParams.p2pkhPrefix,
        scriptHash: cryptoCurrency.networkParams.p2shPrefix,
        wif: cryptoCurrency.networkParams.wifPrefix,
      ),
    );
    txb.setLockTime(await chainHeight);
    txb.setVersion(3 | (9 << 16));

    // final estimated = LibSpark.selectSparkCoins(
    //   requiredAmount: mintVOut.raw.toInt(),
    //   subtractFeeFromAmount: recipientsToSubtractFee > 0,
    //   coins: myCoins,
    //   privateRecipientsCount: txData.sparkRecipients?.length ?? 0,
    // );
    //
    // fee = estimated.fee;
    // bool remainderSubtracted = false;

    // for (int i = 0; i < (txData.recipients?.length ?? 0); i++) {
    //
    //
    //   if (recipient.fSubtractFeeFromAmount) {
    //     // Subtract fee equally from each selected recipient.
    //     recipient.nAmount -= fee / recipientsToSubtractFee;
    //
    //     if (!remainderSubtracted) {
    //       // First receiver pays the remainder not divisible by output count.
    //       recipient.nAmount -= fee % recipientsToSubtractFee;
    //       remainderSubtracted = true;
    //     }
    //   }
    // }

    // outputs

    // for (int i = 0; i < (txData.sparkRecipients?.length ?? 0); i++) {
    //   if (txData.sparkRecipients![i].subtractFeeFromAmount) {
    //     BigInt amount = txData.sparkRecipients![i].amount.raw;
    //
    //     // Subtract fee equally from each selected recipient.
    //     amount -= BigInt.from(fee / recipientsToSubtractFee);
    //
    //     if (!remainderSubtracted) {
    //       // First receiver pays the remainder not divisible by output count.
    //       amount -= BigInt.from(fee % recipientsToSubtractFee);
    //       remainderSubtracted = true;
    //     }
    //
    //     txData.sparkRecipients![i] = (
    //       address: txData.sparkRecipients![i].address,
    //       amount: Amount(
    //         rawValue: amount,
    //         fractionDigits: cryptoCurrency.fractionDigits,
    //       ),
    //       subtractFeeFromAmount:
    //           txData.sparkRecipients![i].subtractFeeFromAmount,
    //       memo: txData.sparkRecipients![i].memo,
    //     );
    //   }
    // }
    //
    // int spendInCurrentTx = 0;
    // for (final spendCoin in estimated.coins) {
    //   spendInCurrentTx += spendCoin.value?.toInt() ?? 0;
    // }
    // spendInCurrentTx -= fee;
    //
    // int transparentOut = 0;

    for (int i = 0; i < (txData.recipients?.length ?? 0); i++) {
      if (txData.recipients![i].amount.raw == BigInt.zero) {
        continue;
      }
      if (txData.recipients![i].amount < cryptoCurrency.dustLimit) {
        throw Exception("Output below dust limit");
      }
      //
      // transparentOut += txData.recipients![i].amount.raw.toInt();
      txb.addOutput(
        txData.recipients![i].address,
        txData.recipients![i].amount.raw.toInt(),
      );
    }

    // // spendInCurrentTx -= transparentOut;
    // final List<({String address, int amount, String memo})> privOutputs = [];
    //
    // for (int i = 0; i < (txData.sparkRecipients?.length ?? 0); i++) {
    //   if (txData.sparkRecipients![i].amount.raw == BigInt.zero) {
    //     continue;
    //   }
    //
    //   final recipientAmount = txData.sparkRecipients![i].amount.raw.toInt();
    //   // spendInCurrentTx -= recipientAmount;
    //
    //   privOutputs.add(
    //     (
    //       address: txData.sparkRecipients![i].address,
    //       amount: recipientAmount,
    //       memo: txData.sparkRecipients![i].memo,
    //     ),
    //   );
    // }

    // if (spendInCurrentTx < 0) {
    //   throw Exception("Unable to create spend transaction.");
    // }
    //
    // if (privOutputs.isEmpty || spendInCurrentTx > 0) {
    //   final changeAddress = await LibSpark.getAddress(
    //     privateKey: privateKey,
    //     index: index,
    //     diversifier: kSparkChange,
    //   );
    //
    //   privOutputs.add(
    //     (
    //       address: changeAddress,
    //       amount: spendInCurrentTx > 0 ? spendInCurrentTx : 0,
    //       memo: "",
    //     ),
    //   );
    // }

    // inputs

    final opReturnScript = bscript.compile([
      0xd3, // OP_SPARKSPEND
      Uint8List(0),
    ]);

    txb.addInput(
      '0000000000000000000000000000000000000000000000000000000000000000',
      0xffffffff,
      0xffffffff,
      opReturnScript,
    );

    // final sig = extractedTx.getId();

    // for (final coin in estimated.coins) {
    //   final groupId = coin.id!;
    // }

    final spend = LibSpark.createSparkSendTransaction(
      privateKeyHex: privateKey.toHex,
      index: kDefaultSparkIndex,
      recipients: [],
      privateRecipients: txData.sparkRecipients
              ?.map((e) => (
                    sparkAddress: e.address,
                    amount: e.amount.raw.toInt(),
                    subtractFeeFromAmount: e.subtractFeeFromAmount,
                    memo: e.memo,
                  ))
              .toList() ??
          [],
      serializedCoins: serializedCoins,
      allAnonymitySets: allAnonymitySets,
    );

    print("SPARK SPEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    print("fee: ${spend.fee}");
    print("spend: ${spend.serializedSpendPayload}");
    print("scripts:");
    spend.outputScripts.forEach(print);
    print("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");

    for (final outputScript in spend.outputScripts) {
      txb.addOutput(outputScript, 0);
    }

    final extractedTx = txb.buildIncomplete();

    // TODO: verify encoding
    extractedTx.setPayload(spend.serializedSpendPayload.toUint8ListFromUtf8);

    final rawTxHex = extractedTx.toHex();

    return txData.copyWith(
      raw: rawTxHex,
      vSize: extractedTx.virtualSize(),
      fee: Amount(
        rawValue: BigInt.from(spend.fee),
        fractionDigits: cryptoCurrency.fractionDigits,
      ),
      // TODO used coins
    );
  }

  // this may not be needed for either mints or spends or both
  Future<TxData> confirmSendSpark({
    required TxData txData,
  }) async {
    throw UnimplementedError();
  }

  // TODO lots of room for performance improvements here. Should be similar to
  // recoverSparkWallet but only fetch and check anonymity set data that we
  // have not yet parsed.
  Future<void> refreshSparkData() async {
    final sparkAddresses = await mainDB.isar.addresses
        .where()
        .walletIdEqualTo(walletId)
        .filter()
        .typeEqualTo(AddressType.spark)
        .findAll();

    final Set<String> paths =
        sparkAddresses.map((e) => e.derivationPath!.value).toSet();

    try {
      final latestSparkCoinId = await electrumXClient.getSparkLatestCoinId();

      final blockHash = await _getCachedSparkBlockHash();

      final anonymitySet = blockHash == null
          ? await electrumXCachedClient.getSparkAnonymitySet(
              groupId: latestSparkCoinId.toString(),
              coin: info.coin,
            )
          : await electrumXClient.getSparkAnonymitySet(
              coinGroupId: latestSparkCoinId.toString(),
              startBlockHash: blockHash,
            );

      if (anonymitySet["coins"] is List &&
          (anonymitySet["coins"] as List).isNotEmpty) {
        final spentCoinTags =
            await electrumXCachedClient.getSparkUsedCoinsTags(coin: info.coin);

        final root = await getRootHDNode();
        final privateKeyHexSet = paths
            .map(
              (e) => root.derivePath(e).privateKey.data.toHex,
            )
            .toSet();

        final myCoins = await compute(
          _identifyCoins,
          (
            anonymitySetCoins: anonymitySet["coins"] as List,
            spentCoinTags: spentCoinTags,
            privateKeyHexSet: privateKeyHexSet,
            walletId: walletId,
            isTestNet: cryptoCurrency.network == CryptoCurrencyNetwork.test,
          ),
        );

        // update wallet spark coins in isar
        await _addOrUpdateSparkCoins(myCoins);

        // update blockHash in cache
        final String newBlockHash =
            base64ToReverseHex(anonymitySet["blockHash"] as String);
        await _setCachedSparkBlockHash(newBlockHash);
      }

      // refresh spark balance
      await refreshSparkBalance();
    } catch (e, s) {
      // todo logging

      rethrow;
    }
  }

  Future<void> refreshSparkBalance() async {
    final currentHeight = await chainHeight;
    final unusedCoins = await mainDB.isar.sparkCoins
        .where()
        .walletIdEqualToAnyLTagHash(walletId)
        .filter()
        .isUsedEqualTo(false)
        .findAll();

    final total = Amount(
      rawValue: unusedCoins
          .map((e) => e.value)
          .fold(BigInt.zero, (prev, e) => prev + e),
      fractionDigits: cryptoCurrency.fractionDigits,
    );
    final spendable = Amount(
      rawValue: unusedCoins
          .where((e) =>
              e.height != null &&
              e.height! + cryptoCurrency.minConfirms >= currentHeight)
          .map((e) => e.value)
          .fold(BigInt.zero, (prev, e) => prev + e),
      fractionDigits: cryptoCurrency.fractionDigits,
    );

    final sparkBalance = Balance(
      total: total,
      spendable: spendable,
      blockedTotal: Amount(
        rawValue: BigInt.zero,
        fractionDigits: cryptoCurrency.fractionDigits,
      ),
      pendingSpendable: total - spendable,
    );

    await info.updateBalanceTertiary(
      newBalance: sparkBalance,
      isar: mainDB.isar,
    );
  }

  /// Should only be called within the standard wallet [recover] function due to
  /// mutex locking. Otherwise behaviour MAY be undefined.
  Future<void> recoverSparkWallet({
    required Map<dynamic, dynamic> anonymitySet,
    required Set<String> spentCoinTags,
  }) async {
    //   generate spark addresses if non existing
    if (await getCurrentReceivingSparkAddress() == null) {
      final address = await generateNextSparkAddress();
      await mainDB.putAddress(address);
    }

    final sparkAddresses = await mainDB.isar.addresses
        .where()
        .walletIdEqualTo(walletId)
        .filter()
        .typeEqualTo(AddressType.spark)
        .findAll();

    final Set<String> paths =
        sparkAddresses.map((e) => e.derivationPath!.value).toSet();

    try {
      final root = await getRootHDNode();
      final privateKeyHexSet =
          paths.map((e) => root.derivePath(e).privateKey.data.toHex).toSet();

      final myCoins = await compute(
        _identifyCoins,
        (
          anonymitySetCoins: anonymitySet["coins"] as List,
          spentCoinTags: spentCoinTags,
          privateKeyHexSet: privateKeyHexSet,
          walletId: walletId,
          isTestNet: cryptoCurrency.network == CryptoCurrencyNetwork.test,
        ),
      );

      // update wallet spark coins in isar
      await _addOrUpdateSparkCoins(myCoins);

      // update blockHash in cache
      final String newBlockHash = anonymitySet["blockHash"] as String;
      await _setCachedSparkBlockHash(newBlockHash);

      // refresh spark balance
      await refreshSparkBalance();
    } catch (e, s) {
      // todo logging

      rethrow;
    }
  }

  /// Transparent to Spark (mint) transaction creation.
  ///
  /// See https://docs.google.com/document/d/1RG52GoYTZDvKlZz_3G4sQu-PpT6JWSZGHLNswWcrE3o
  Future<TxData> prepareSparkMintTransaction({required TxData txData}) async {
    // "this kind of transaction is generated like a regular transaction, but in
    // place of [regular] outputs we put spark outputs... we construct the input
    // part of the transaction first then we generate spark related data [and]
    // we sign like regular transactions at the end."

    // Validate inputs.

    // There should be at least one input.
    if (txData.utxos == null || txData.utxos!.isEmpty) {
      throw Exception("No inputs provided.");
    }

    // Validate individual inputs.
    for (final utxo in txData.utxos!) {
      // Input amount must be greater than zero.
      if (utxo.value == 0) {
        throw Exception("Input value cannot be zero.");
      }

      // Input value must be greater than dust limit.
      if (BigInt.from(utxo.value) < cryptoCurrency.dustLimit.raw) {
        throw Exception("Input value below dust limit.");
      }
    }

    // Validate outputs.

    // There should be at least one output.
    if (txData.recipients == null || txData.recipients!.isEmpty) {
      throw Exception("No recipients provided.");
    }

    // For now let's limit to one output.
    if (txData.recipients!.length > 1) {
      throw Exception("Only one recipient supported.");
      // TODO remove and test with multiple recipients.
    }

    // Limit outputs per tx to 16.
    //
    // See SPARK_OUT_LIMIT_PER_TX at https://github.com/firoorg/sparkmobile/blob/ef2e39aae18ecc49e0ddc63a3183e9764b96012e/include/spark.h#L16
    if (txData.recipients!.length > 16) {
      throw Exception("Too many recipients.");
    }

    // Limit spend value per tx to 1000000000000 satoshis.
    //
    // See SPARK_VALUE_SPEND_LIMIT_PER_TRANSACTION at https://github.com/firoorg/sparkmobile/blob/ef2e39aae18ecc49e0ddc63a3183e9764b96012e/include/spark.h#L17
    // and COIN https://github.com/firoorg/sparkmobile/blob/ef2e39aae18ecc49e0ddc63a3183e9764b96012e/bitcoin/amount.h#L17
    // Note that as MAX_MONEY is greater than this limit, we can ignore it.  See https://github.com/firoorg/sparkmobile/blob/ef2e39aae18ecc49e0ddc63a3183e9764b96012e/bitcoin/amount.h#L31
    //
    // This will be added to and checked as we validate outputs.
    Amount totalAmount = Amount(
      rawValue: BigInt.zero,
      fractionDigits: cryptoCurrency.fractionDigits,
    );

    // Validate individual outputs.
    for (final recipient in txData.recipients!) {
      // Output amount must be greater than zero.
      if (recipient.amount.raw == BigInt.zero) {
        throw Exception("Output amount cannot be zero.");
        // Could refactor this for loop to use an index and remove this output.
      }

      // Output amount must be greater than dust limit.
      if (recipient.amount < cryptoCurrency.dustLimit) {
        throw Exception("Output below dust limit.");
      }

      // Do not add outputs that would exceed the spend limit.
      totalAmount += recipient.amount;
      if (totalAmount.raw > BigInt.from(1000000000000)) {
        throw Exception(
          "Spend limit exceeded (10,000 FIRO per tx).",
        );
      }
    }

    // Create a transaction builder and set locktime and version.
    final txb = btc.TransactionBuilder(
      network: btc.NetworkType(
        messagePrefix: cryptoCurrency.networkParams.messagePrefix,
        bech32: cryptoCurrency.networkParams.bech32Hrp,
        bip32: btc.Bip32Type(
          public: cryptoCurrency.networkParams.pubHDPrefix,
          private: cryptoCurrency.networkParams.privHDPrefix,
        ),
        pubKeyHash: cryptoCurrency.networkParams.p2pkhPrefix,
        scriptHash: cryptoCurrency.networkParams.p2shPrefix,
        wif: cryptoCurrency.networkParams.wifPrefix,
      ),
    );
    txb.setLockTime(await chainHeight);
    txb.setVersion(1);

    final signingData = await fetchBuildTxData(txData.utxos!.toList());

    // Create the serial context.
    //
    // "...serial_context is a byte array, which should be unique for each
    // transaction, and for that we serialize and put all inputs into
    // serial_context vector."
    final serialContext = LibSpark.serializeMintContext(
      inputs: signingData
          .map((e) => (
                e.utxo.txid,
                e.utxo.vout,
              ))
          .toList(),
    );

    // Add inputs.
    for (final sd in signingData) {
      txb.addInput(
        sd.utxo.txid,
        sd.utxo.vout,
        0xffffffff -
            1, // minus 1 is important. 0xffffffff on its own will burn funds
        sd.output,
      );
    }

    // Create mint recipients.
    final mintRecipients = LibSpark.createSparkMintRecipients(
      outputs: txData.recipients!
          .map((e) => (
                sparkAddress: e.address,
                value: e.amount.raw.toInt(),
                memo: "",
              ))
          .toList(),
      serialContext: Uint8List.fromList(serialContext),
      generate: true,
    );

    // Add mint output(s).
    for (final mint in mintRecipients) {
      txb.addOutput(
        mint.scriptPubKey,
        mint.amount,
      );
    }

    try {
      // Sign the transaction accordingly
      for (var i = 0; i < signingData.length; i++) {
        txb.sign(
          vin: i,
          keyPair: signingData[i].keyPair!,
          witnessValue: signingData[i].utxo.value,
          redeemScript: signingData[i].redeemScript,
        );
      }
    } catch (e, s) {
      Logging.instance.log(
        "Caught exception while signing spark mint transaction: $e\n$s",
        level: LogLevel.Error,
      );
      rethrow;
    }

    final builtTx = txb.build();

    // TODO any changes to this txData object required?
    return txData.copyWith(
      // recipients: [
      //   (
      //   amount: Amount(
      //     rawValue: BigInt.from(incomplete.outs[0].value!),
      //     fractionDigits: cryptoCurrency.fractionDigits,
      //   ),
      //   address: "no address for lelantus mints",
      //   )
      // ],
      vSize: builtTx.virtualSize(),
      txid: builtTx.getId(),
      raw: builtTx.toHex(),
    );
  }

  /// Broadcast a tx and TODO update Spark balance.
  Future<TxData> confirmSparkMintTransaction({required TxData txData}) async {
    // Broadcast tx.
    final txid = await electrumXClient.broadcastTransaction(
      rawTx: txData.raw!,
    );

    // Check txid.
    if (txid == txData.txid!) {
      print("SPARK TXIDS MATCH!!");
    } else {
      print("SUBMITTED SPARK TXID DOES NOT MATCH WHAT WE GENERATED");
    }

    // TODO update spark balance.

    return txData.copyWith(
      txid: txid,
    );
  }

  @override
  Future<void> updateBalance() async {
    // call to super to update transparent balance (and lelantus balance if
    // what ever class this mixin is used on uses LelantusInterface as well)
    final normalBalanceFuture = super.updateBalance();

    // todo: spark balance aka update info.tertiaryBalance

    // wait for normalBalanceFuture to complete before returning
    await normalBalanceFuture;
  }

  // ====================== Private ============================================

  final _kSparkAnonSetCachedBlockHashKey = "SparkAnonSetCachedBlockHashKey";

  Future<String?> _getCachedSparkBlockHash() async {
    return info.otherData[_kSparkAnonSetCachedBlockHashKey] as String?;
  }

  Future<void> _setCachedSparkBlockHash(String blockHash) async {
    await info.updateOtherData(
      newEntries: {_kSparkAnonSetCachedBlockHashKey: blockHash},
      isar: mainDB.isar,
    );
  }

  Future<void> _addOrUpdateSparkCoins(List<SparkCoin> coins) async {
    if (coins.isNotEmpty) {
      await mainDB.isar.writeTxn(() async {
        await mainDB.isar.sparkCoins.putAll(coins);
      });
    }

    // update wallet spark coin height
    final coinsToCheck = await mainDB.isar.sparkCoins
        .where()
        .walletIdEqualToAnyLTagHash(walletId)
        .filter()
        .heightIsNull()
        .findAll();
    final List<SparkCoin> updatedCoins = [];
    for (final coin in coinsToCheck) {
      final tx = await electrumXCachedClient.getTransaction(
        txHash: coin.txHash,
        coin: info.coin,
      );
      if (tx["height"] is int) {
        updatedCoins.add(coin.copyWith(height: tx["height"] as int));
      }
    }
    if (updatedCoins.isNotEmpty) {
      await mainDB.isar.writeTxn(() async {
        await mainDB.isar.sparkCoins.putAll(updatedCoins);
      });
    }
  }
}

String base64ToReverseHex(String source) =>
    base64Decode(LineSplitter.split(source).join())
        .reversed
        .map((e) => e.toRadixString(16).padLeft(2, '0'))
        .join();

/// Top level function which should be called wrapped in [compute]
Future<List<SparkCoin>> _identifyCoins(
    ({
      List<dynamic> anonymitySetCoins,
      Set<String> spentCoinTags,
      Set<String> privateKeyHexSet,
      String walletId,
      bool isTestNet,
    }) args) async {
  final List<SparkCoin> myCoins = [];

  for (final privateKeyHex in args.privateKeyHexSet) {
    for (final dynData in args.anonymitySetCoins) {
      final data = List<String>.from(dynData as List);

      if (data.length != 3) {
        throw Exception("Unexpected serialized coin info found");
      }

      final serializedCoinB64 = data[0];
      final txHash = base64ToReverseHex(data[1]);
      final contextB64 = data[2];

      final coin = LibSpark.identifyAndRecoverCoin(
        serializedCoinB64,
        privateKeyHex: privateKeyHex,
        index: kDefaultSparkIndex,
        context: base64Decode(contextB64),
        isTestNet: args.isTestNet,
      );

      // its ours
      if (coin != null) {
        final SparkCoinType coinType;
        switch (coin.type.value) {
          case 0:
            coinType = SparkCoinType.mint;
          case 1:
            coinType = SparkCoinType.spend;
          default:
            throw Exception("Unknown spark coin type detected");
        }
        myCoins.add(
          SparkCoin(
            walletId: args.walletId,
            type: coinType,
            isUsed: args.spentCoinTags.contains(coin.lTagHash!),
            nonce: coin.nonceHex?.toUint8ListFromHex,
            address: coin.address!,
            txHash: txHash,
            valueIntString: coin.value!.toString(),
            memo: coin.memo,
            serialContext: coin.serialContext,
            diversifierIntString: coin.diversifier!.toString(),
            encryptedDiversifier: coin.encryptedDiversifier,
            serial: coin.serial,
            tag: coin.tag,
            lTagHash: coin.lTagHash!,
            height: coin.height,
            serializedCoinB64: serializedCoinB64,
            contextB64: contextB64,
          ),
        );
      }
    }
  }

  return myCoins;
}