text: // Copyright (c) 2017 The Bitcoin Core developers
  // Copyright (c) 2019 The Swyft Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <consensus/validation.h>
  #include <wallet/coincontrol.h>
  #include <wallet/feebumper.h>
  #include <wallet/fees.h>
  #include <wallet/wallet.h>
  #include <policy/fees.h>
  #include <policy/policy.h>
  #include <policy/rbf.h>
  #include <validation.h> //for mempool access
  #include <txmempool.h>
  #include <utilmoneystr.h>
  #include <util.h>
  #include <net.h>
  
  //! Check whether transaction has descendant in wallet or mempool, or has been
  //! mined, or conflicts with a mined transaction. Return a feebumper::Result.
  static feebumper::Result PreconditionChecks(const CWallet* wallet, const CWalletTx& wtx, std::vector<std::string>& errors) EXCLUSIVE_LOCKS_REQUIRED(wallet->cs_wallet)
  {
      if (wallet->HasWalletSpend(wtx.GetHash())) {
          errors.push_back("Transaction has descendants in the wallet");
          return feebumper::Result::INVALID_PARAMETER;
      }
  
      {
          LOCK(mempool.cs);
          auto it_mp = mempool.mapTx.find(wtx.GetHash());
          if (it_mp != mempool.mapTx.end() && it_mp->GetCountWithDescendants() > 1) {
              errors.push_back("Transaction has descendants in the mempool");
              return feebumper::Result::INVALID_PARAMETER;
          }
      }
  
      if (wtx.GetDepthInMainChain() != 0) {
          errors.push_back("Transaction has been mined, or is conflicted with a mined transaction");
          return feebumper::Result::WALLET_ERROR;
      }
  
      if (!SignalsOptInRBF(*wtx.tx)) {
          errors.push_back("Transaction is not BIP 125 replaceable");
          return feebumper::Result::WALLET_ERROR;
      }
  
      if (wtx.mapValue.count("replaced_by_txid")) {
          errors.push_back(strprintf("Cannot bump transaction %s which was already bumped by transaction %s", wtx.GetHash().ToString(), wtx.mapValue.at("replaced_by_txid")));
          return feebumper::Result::WALLET_ERROR;
      }
  
      // check that original tx consists entirely of our inputs
      // if not, we can't bump the fee, because the wallet has no way of knowing the value of the other inputs (thus the fee)
      if (!wallet->IsAllFromMe(*wtx.tx, ISMINE_SPENDABLE)) {
          errors.push_back("Transaction contains inputs that don't belong to this wallet");
          return feebumper::Result::WALLET_ERROR;
      }
  
  
      return feebumper::Result::OK;
  }
  
  namespace feebumper {
  
  bool TransactionCanBeBumped(const CWallet* wallet, const uint256& txid)
  {
      LOCK2(cs_main, wallet->cs_wallet);
      const CWalletTx* wtx = wallet->GetWalletTx(txid);
      if (wtx == nullptr) return false;
  
      std::vector<std::string> errors_dummy;
      feebumper::Result res = PreconditionChecks(wallet, *wtx, errors_dummy);
      return res == feebumper::Result::OK;
  }
  
  Result CreateTransaction(const CWallet* wallet, const uint256& txid, const CCoinControl& coin_control, CAmount total_fee, std::vector<std::string>& errors,
                           CAmount& old_fee, CAmount& new_fee, CMutableTransaction& mtx)
  {
      LOCK2(cs_main, wallet->cs_wallet);
      errors.clear();
      auto it = wallet->mapWallet.find(txid);
      if (it == wallet->mapWallet.end()) {
          errors.push_back("Invalid or non-wallet transaction id");
          return Result::INVALID_ADDRESS_OR_KEY;
      }
      const CWalletTx& wtx = it->second;
  
      Result result = PreconditionChecks(wallet, wtx, errors);
      if (result != Result::OK) {
          return result;
      }
  
      // figure out which output was change
      // if there was no change output or multiple change outputs, fail
      int nOutput = -1;
      for (size_t i = 0; i < wtx.tx->vout.size(); ++i) {
          if (wallet->IsChange(wtx.tx->vout[i])) {
              if (nOutput != -1) {
                  errors.push_back("Transaction has multiple change outputs");
                  return Result::WALLET_ERROR;
              }
              nOutput = i;
          }
      }
      if (nOutput == -1) {
          errors.push_back("Transaction does not have a change output");
          return Result::WALLET_ERROR;
      }
  
      // Calculate the expected size of the new transaction.
      int64_t txSize = GetVirtualTransactionSize(*(wtx.tx));
      const int64_t maxNewTxSize = CalculateMaximumSignedTxSize(*wtx.tx, wallet);
      if (maxNewTxSize < 0) {
          errors.push_back("Transaction contains inputs that cannot be signed");
          return Result::INVALID_ADDRESS_OR_KEY;
      }
  
      // calculate the old fee and fee-rate
      old_fee = wtx.GetDebit(ISMINE_SPENDABLE) - wtx.tx->GetValueOut();
      CFeeRate nOldFeeRate(old_fee, txSize);
      CFeeRate nNewFeeRate;
      // The wallet uses a conservative WALLET_INCREMENTAL_RELAY_FEE value to
      // future proof against changes to network wide policy for incremental relay
      // fee that our node may not be aware of.
      CFeeRate walletIncrementalRelayFee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
      if (::incrementalRelayFee > walletIncrementalRelayFee) {
          walletIncrementalRelayFee = ::incrementalRelayFee;
      }
  
      if (total_fee > 0) {
          CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + ::incrementalRelayFee.GetFee(maxNewTxSize);
          if (total_fee < minTotalFee) {
              errors.push_back(strprintf("Insufficient totalFee, must be at least %s (oldFee %s + incrementalFee %s)",
                                                                  FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxNewTxSize)), FormatMoney(::incrementalRelayFee.GetFee(maxNewTxSize))));
              return Result::INVALID_PARAMETER;
          }
          CAmount requiredFee = GetRequiredFee(*wallet, maxNewTxSize);
          if (total_fee < requiredFee) {
              errors.push_back(strprintf("Insufficient totalFee (cannot be less than required fee %s)",
                                                                  FormatMoney(requiredFee)));
              return Result::INVALID_PARAMETER;
          }
          new_fee = total_fee;
          nNewFeeRate = CFeeRate(total_fee, maxNewTxSize);
      } else {
          new_fee = GetMinimumFee(*wallet, maxNewTxSize, coin_control, mempool, ::feeEstimator, nullptr /* FeeCalculation */);
          nNewFeeRate = CFeeRate(new_fee, maxNewTxSize);
  
          // New fee rate must be at least old rate + minimum incremental relay rate
          // walletIncrementalRelayFee.GetFeePerK() should be exact, because it's initialized
          // in that unit (fee per kb).
          // However, nOldFeeRate is a calculated value from the tx fee/size, so
          // add 1 satoshi to the result, because it may have been rounded down.
          if (nNewFeeRate.GetFeePerK() < nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK()) {
              nNewFeeRate = CFeeRate(nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK());
              new_fee = nNewFeeRate.GetFee(maxNewTxSize);
          }
      }
  
      // Check that in all cases the new fee doesn't violate maxTxFee
       if (new_fee > maxTxFee) {
           errors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than maxTxFee %s)",
                                 FormatMoney(new_fee), FormatMoney(maxTxFee)));
           return Result::WALLET_ERROR;
       }
  
      // check that fee rate is higher than mempool's minimum fee
      // (no point in bumping fee if we know that the new tx won't be accepted to the mempool)
      // This may occur if the user set TotalFee or paytxfee too low, if fallbackfee is too low, or, perhaps,
      // in a rare situation where the mempool minimum fee increased significantly since the fee estimation just a
      // moment earlier. In this case, we report an error to the user, who may use total_fee to make an adjustment.
      CFeeRate minMempoolFeeRate = mempool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
      if (nNewFeeRate.GetFeePerK() < minMempoolFeeRate.GetFeePerK()) {
          errors.push_back(strprintf(
              "New fee rate (%s) is lower than the minimum fee rate (%s) to get into the mempool -- "
              "the totalFee value should be at least %s or the settxfee value should be at least %s to add transaction",
              FormatMoney(nNewFeeRate.GetFeePerK()),
              FormatMoney(minMempoolFeeRate.GetFeePerK()),
              FormatMoney(minMempoolFeeRate.GetFee(maxNewTxSize)),
              FormatMoney(minMempoolFeeRate.GetFeePerK())));
          return Result::WALLET_ERROR;
      }
  
      // Now modify the output to increase the fee.
      // If the output is not large enough to pay the fee, fail.
      CAmount nDelta = new_fee - old_fee;
      assert(nDelta > 0);
      mtx =  *wtx.tx;
      CTxOut* poutput = &(mtx.vout[nOutput]);
      if (poutput->nValue < nDelta) {
          errors.push_back("Change output is too small to bump the fee");
          return Result::WALLET_ERROR;
      }
  
      // If the output would become dust, discard it (converting the dust to fee)
      poutput->nValue -= nDelta;
      if (poutput->nValue <= GetDustThreshold(*poutput, GetDiscardRate(*wallet, ::feeEstimator))) {
          LogPrint(BCLog::RPC, "Bumping fee and discarding dust output\n");
          new_fee += poutput->nValue;
          mtx.vout.erase(mtx.vout.begin() + nOutput);
      }
  
      // Mark new tx not replaceable, if requested.
      if (!coin_control.m_signal_bip125_rbf.get_value_or(wallet->m_signal_rbf)) {
          for (auto& input : mtx.vin) {
              if (input.nSequence < 0xfffffffe) input.nSequence = 0xfffffffe;
          }
      }
  
  
      return Result::OK;
  }
  
  bool SignTransaction(CWallet* wallet, CMutableTransaction& mtx) {
      LOCK2(cs_main, wallet->cs_wallet);
      return wallet->SignTransaction(mtx);
  }
  
  Result CommitTransaction(CWallet* wallet, const uint256& txid, CMutableTransaction&& mtx, std::vector<std::string>& errors, uint256& bumped_txid)
  {
      LOCK2(cs_main, wallet->cs_wallet);
      if (!errors.empty()) {
          return Result::MISC_ERROR;
      }
      auto it = txid.IsNull() ? wallet->mapWallet.end() : wallet->mapWallet.find(txid);
      if (it == wallet->mapWallet.end()) {
          errors.push_back("Invalid or non-wallet transaction id");
          return Result::MISC_ERROR;
      }
      CWalletTx& oldWtx = it->second;
  
      // make sure the transaction still has no descendants and hasn't been mined in the meantime
      Result result = PreconditionChecks(wallet, oldWtx, errors);
      if (result != Result::OK) {
          return result;
      }
  
      // commit/broadcast the tx
      CTransactionRef tx = MakeTransactionRef(std::move(mtx));
      mapValue_t mapValue = oldWtx.mapValue;
      mapValue["replaces_txid"] = oldWtx.GetHash().ToString();
  
      CReserveKey reservekey(wallet);
      CValidationState state;
      if (!wallet->CommitTransaction(tx, std::move(mapValue), oldWtx.vOrderForm, oldWtx.strFromAccount, reservekey, g_connman.get(), state)) {
          // NOTE: CommitTransaction never returns false, so this should never happen.
          errors.push_back(strprintf("The transaction was rejected: %s", FormatStateMessage(state)));
          return Result::WALLET_ERROR;
      }
  
      bumped_txid = tx->GetHash();
      if (state.IsInvalid()) {
          // This can happen if the mempool rejected the transaction.  Report
          // what happened in the "errors" response.
          errors.push_back(strprintf("Error: The transaction was rejected: %s", FormatStateMessage(state)));
      }
  
      // mark the original tx as bumped
      if (!wallet->MarkReplaced(oldWtx.GetHash(), bumped_txid)) {
          // TODO: see if JSON-RPC has a standard way of returning a response
          // along with an exception. It would be good to return information about
          // wtxBumped to the caller even if marking the original transaction
          // replaced does not succeed for some reason.
          errors.push_back("Created new bumpfee transaction but could not mark the original transaction as replaced");
      }
      return Result::OK;
  }
  
  } // namespace feebumper
  