text: // Copyright (c) 2017-2019 The Eozi 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 <interfaces/chain.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 <util/moneystr.h>
  #include <util/rbf.h>
  #include <util/system.h>
  #include <util/validation.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(interfaces::Chain::Lock& locked_chain, 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;
      }
  
      {
          if (wallet->chain().hasDescendantsInMempool(wtx.GetHash())) {
              errors.push_back("Transaction has descendants in the mempool");
              return feebumper::Result::INVALID_PARAMETER;
          }
      }
  
      if (wtx.GetDepthInMainChain(locked_chain) != 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;
  }
  
  //! Check if the user provided a valid feeRate
  static feebumper::Result CheckFeeRate(const CWallet* wallet, const CWalletTx& wtx, const CFeeRate& newFeerate, const int64_t maxTxSize, std::vector<std::string>& errors) {
      // 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 FeeRate, 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 adjust the fee.
      CFeeRate minMempoolFeeRate = wallet->chain().mempoolMinFee();
  
      if (newFeerate.GetFeePerK() < minMempoolFeeRate.GetFeePerK()) {
          errors.push_back(strprintf(
              "New fee rate (%s) is lower than the minimum fee rate (%s) to get into the mempool -- ",
              FormatMoney(newFeerate.GetFeePerK()),
              FormatMoney(minMempoolFeeRate.GetFeePerK())));
          return feebumper::Result::WALLET_ERROR;
      }
  
      CAmount new_total_fee = newFeerate.GetFee(maxTxSize);
  
      CFeeRate incrementalRelayFee = std::max(wallet->chain().relayIncrementalFee(), CFeeRate(WALLET_INCREMENTAL_RELAY_FEE));
  
      // Given old total fee and transaction size, calculate the old feeRate
      CAmount old_fee = wtx.GetDebit(ISMINE_SPENDABLE) - wtx.tx->GetValueOut();
      const int64_t txSize = GetVirtualTransactionSize(*(wtx.tx));
      CFeeRate nOldFeeRate(old_fee, txSize);
      // Min total fee is old fee + relay fee
      CAmount minTotalFee = nOldFeeRate.GetFee(maxTxSize) + incrementalRelayFee.GetFee(maxTxSize);
  
      if (new_total_fee < minTotalFee) {
          errors.push_back(strprintf("Insufficient total fee %s, must be at least %s (oldFee %s + incrementalFee %s)",
              FormatMoney(new_total_fee), FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxTxSize)), FormatMoney(incrementalRelayFee.GetFee(maxTxSize))));
          return feebumper::Result::INVALID_PARAMETER;
      }
  
      CAmount requiredFee = GetRequiredFee(*wallet, maxTxSize);
      if (new_total_fee < requiredFee) {
          errors.push_back(strprintf("Insufficient total fee (cannot be less than required fee %s)",
              FormatMoney(requiredFee)));
          return feebumper::Result::INVALID_PARAMETER;
      }
  
      // Check that in all cases the new fee doesn't violate maxTxFee
      const CAmount max_tx_fee = wallet->m_default_max_tx_fee;
      if (new_total_fee > max_tx_fee) {
          errors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than -maxtxfee %s)",
                              FormatMoney(new_total_fee), FormatMoney(max_tx_fee)));
          return feebumper::Result::WALLET_ERROR;
      }
  
      return feebumper::Result::OK;
  }
  
  static CFeeRate EstimateFeeRate(CWallet* wallet, const CWalletTx& wtx, const CAmount old_fee, CCoinControl& coin_control)
  {
      // Get the fee rate of the original transaction. This is calculated from
      // the tx fee/vsize, so it may have been rounded down. Add 1 satoshi to the
      // result.
      int64_t txSize = GetVirtualTransactionSize(*(wtx.tx));
      CFeeRate feerate(old_fee, txSize);
      feerate += CFeeRate(1);
  
      // The node has a configurable incremental relay fee. Increment the fee by
      // the minimum of that and the wallet's 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. This ensures we're over the over the required relay fee rate
      // (BIP 125 rule 4).  The replacement tx will be at least as large as the
      // original tx, so the total fee will be greater (BIP 125 rule 3)
      CFeeRate node_incremental_relay_fee = wallet->chain().relayIncrementalFee();
      CFeeRate wallet_incremental_relay_fee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
      feerate += std::max(node_incremental_relay_fee, wallet_incremental_relay_fee);
  
      // Fee rate must also be at least the wallet's GetMinimumFeeRate
      CFeeRate min_feerate(GetMinimumFeeRate(*wallet, coin_control, /* feeCalc */ nullptr));
  
      // Set the required fee rate for the replacement transaction in coin control.
      return std::max(feerate, min_feerate);
  }
  
  namespace feebumper {
  
  bool TransactionCanBeBumped(const CWallet* wallet, const uint256& txid)
  {
      auto locked_chain = wallet->chain().lock();
      LOCK(wallet->cs_wallet);
      const CWalletTx* wtx = wallet->GetWalletTx(txid);
      if (wtx == nullptr) return false;
  
      std::vector<std::string> errors_dummy;
      feebumper::Result res = PreconditionChecks(*locked_chain, wallet, *wtx, errors_dummy);
      return res == feebumper::Result::OK;
  }
  
  Result CreateTotalBumpTransaction(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)
  {
      new_fee = total_fee;
  
      auto locked_chain = wallet->chain().lock();
      LOCK(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(*locked_chain, 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);
      // 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 nodeIncrementalRelayFee = wallet->chain().relayIncrementalFee();
      CFeeRate walletIncrementalRelayFee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
      if (nodeIncrementalRelayFee > walletIncrementalRelayFee) {
          walletIncrementalRelayFee = nodeIncrementalRelayFee;
      }
  
      CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + nodeIncrementalRelayFee.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(nodeIncrementalRelayFee.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;
      }
  
      // Check that in all cases the new fee doesn't violate maxTxFee
       const CAmount max_tx_fee = wallet->m_default_max_tx_fee;
       if (new_fee > max_tx_fee) {
           errors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than -maxtxfee %s)",
                                 FormatMoney(new_fee), FormatMoney(max_tx_fee)));
           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 = wallet->chain().mempoolMinFee();
      CFeeRate nNewFeeRate = CFeeRate(total_fee, maxNewTxSize);
      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 to add transaction",
              FormatMoney(nNewFeeRate.GetFeePerK()),
              FormatMoney(minMempoolFeeRate.GetFeePerK()),
              FormatMoney(minMempoolFeeRate.GetFee(maxNewTxSize))));
          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 = CMutableTransaction{*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))) {
          wallet->WalletLogPrintf("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;
  }
  
  
  Result CreateRateBumpTransaction(CWallet* wallet, const uint256& txid, const CCoinControl& coin_control, std::vector<std::string>& errors,
                                   CAmount& old_fee, CAmount& new_fee, CMutableTransaction& mtx)
  {
      // We are going to modify coin control later, copy to re-use
      CCoinControl new_coin_control(coin_control);
  
      auto locked_chain = wallet->chain().lock();
      LOCK(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(*locked_chain, wallet, wtx, errors);
      if (result != Result::OK) {
          return result;
      }
  
      // Fill in recipients(and preserve a single change key if there is one)
      std::vector<CRecipient> recipients;
      for (const auto& output : wtx.tx->vout) {
          if (!wallet->IsChange(output)) {
              CRecipient recipient = {output.scriptPubKey, output.nValue, false};
              recipients.push_back(recipient);
          } else {
              CTxDestination change_dest;
              ExtractDestination(output.scriptPubKey, change_dest);
              new_coin_control.destChange = change_dest;
          }
      }
  
      old_fee = wtx.GetDebit(ISMINE_SPENDABLE) - wtx.tx->GetValueOut();
  
      if (coin_control.m_feerate) {
          // The user provided a feeRate argument.
          // We calculate this here to avoid compiler warning on the cs_wallet lock
          const int64_t maxTxSize = CalculateMaximumSignedTxSize(*wtx.tx, wallet);
          Result res = CheckFeeRate(wallet, wtx, *(new_coin_control.m_feerate), maxTxSize, errors);
          if (res != Result::OK) {
              return res;
          }
      } else {
          // The user did not provide a feeRate argument
          new_coin_control.m_feerate = EstimateFeeRate(wallet, wtx, old_fee, new_coin_control);
      }
  
      // Fill in required inputs we are double-spending(all of them)
      // N.B.: bip125 doesn't require all the inputs in the replaced transaction to be
      // used in the replacement transaction, but it's very important for wallets to make
      // sure that happens. If not, it would be possible to bump a transaction A twice to
      // A2 and A3 where A2 and A3 don't conflict (or alternatively bump A to A2 and A2
      // to A3 where A and A3 don't conflict). If both later get confirmed then the sender
      // has accidentally double paid.
      for (const auto& inputs : wtx.tx->vin) {
          new_coin_control.Select(COutPoint(inputs.prevout));
      }
      new_coin_control.fAllowOtherInputs = true;
  
      // We cannot source new unconfirmed inputs(bip125 rule 2)
      new_coin_control.m_min_depth = 1;
  
      CTransactionRef tx_new = MakeTransactionRef();
      CAmount fee_ret;
      int change_pos_in_out = -1; // No requested location for change
      std::string fail_reason;
      if (!wallet->CreateTransaction(*locked_chain, recipients, tx_new, fee_ret, change_pos_in_out, fail_reason, new_coin_control, false)) {
          errors.push_back("Unable to create transaction: " + fail_reason);
          return Result::WALLET_ERROR;
      }
  
      // Write back new fee if successful
      new_fee = fee_ret;
  
      // Write back transaction
      mtx = CMutableTransaction(*tx_new);
      // 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) {
      auto locked_chain = wallet->chain().lock();
      LOCK(wallet->cs_wallet);
      return wallet->SignTransaction(mtx);
  }
  
  Result CommitTransaction(CWallet* wallet, const uint256& txid, CMutableTransaction&& mtx, std::vector<std::string>& errors, uint256& bumped_txid)
  {
      auto locked_chain = wallet->chain().lock();
      LOCK(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(*locked_chain, 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();
  
      CValidationState state;
      if (!wallet->CommitTransaction(tx, std::move(mapValue), oldWtx.vOrderForm, 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
  