text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2019 The BitRub Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <wallet/fees.h>
  
  #include <wallet/coincontrol.h>
  #include <wallet/wallet.h>
  
  
  CAmount GetRequiredFee(const CWallet& wallet, unsigned int nTxBytes)
  {
      return GetRequiredFeeRate(wallet).GetFee(nTxBytes);
  }
  
  
  CAmount GetMinimumFee(const CWallet& wallet, unsigned int nTxBytes, const CCoinControl& coin_control, FeeCalculation* feeCalc)
  {
      return GetMinimumFeeRate(wallet, coin_control, feeCalc).GetFee(nTxBytes);
  }
  
  CFeeRate GetRequiredFeeRate(const CWallet& wallet)
  {
      return std::max(wallet.m_min_fee, wallet.chain().relayMinFee());
  }
  
  CFeeRate GetMinimumFeeRate(const CWallet& wallet, const CCoinControl& coin_control, FeeCalculation* feeCalc)
  {
      /* User control of how to calculate fee uses the following parameter precedence:
         1. coin_control.m_feerate
         2. coin_control.m_confirm_target
         3. m_pay_tx_fee (user-set member variable of wallet)
         4. m_confirm_target (user-set member variable of wallet)
         The first parameter that is set is used.
      */
      CFeeRate feerate_needed;
      if (coin_control.m_feerate) { // 1.
          feerate_needed = *(coin_control.m_feerate);
          if (feeCalc) feeCalc->reason = FeeReason::PAYTXFEE;
          // Allow to override automatic min/max check over coin control instance
          if (coin_control.fOverrideFeeRate) return feerate_needed;
      }
      else if (!coin_control.m_confirm_target && wallet.m_pay_tx_fee != CFeeRate(0)) { // 3. TODO: remove magic value of 0 for wallet member m_pay_tx_fee
          feerate_needed = wallet.m_pay_tx_fee;
          if (feeCalc) feeCalc->reason = FeeReason::PAYTXFEE;
      }
      else { // 2. or 4.
          // We will use smart fee estimation
          unsigned int target = coin_control.m_confirm_target ? *coin_control.m_confirm_target : wallet.m_confirm_target;
          // By default estimates are economical iff we are signaling opt-in-RBF
          bool conservative_estimate = !coin_control.m_signal_bip125_rbf.get_value_or(wallet.m_signal_rbf);
          // Allow to override the default fee estimate mode over the CoinControl instance
          if (coin_control.m_fee_mode == FeeEstimateMode::CONSERVATIVE) conservative_estimate = true;
          else if (coin_control.m_fee_mode == FeeEstimateMode::ECONOMICAL) conservative_estimate = false;
  
          feerate_needed = wallet.chain().estimateSmartFee(target, conservative_estimate, feeCalc);
          if (feerate_needed == CFeeRate(0)) {
              // if we don't have enough data for estimateSmartFee, then use fallback fee
              feerate_needed = wallet.m_fallback_fee;
              if (feeCalc) feeCalc->reason = FeeReason::FALLBACK;
  
              // directly return if fallback fee is disabled (feerate 0 == disabled)
              if (wallet.m_fallback_fee == CFeeRate(0)) return feerate_needed;
          }
          // Obey mempool min fee when using smart fee estimation
          CFeeRate min_mempool_feerate = wallet.chain().mempoolMinFee();
          if (feerate_needed < min_mempool_feerate) {
              feerate_needed = min_mempool_feerate;
              if (feeCalc) feeCalc->reason = FeeReason::MEMPOOL_MIN;
          }
      }
  
      // prevent user from paying a fee below the required fee rate
      CFeeRate required_feerate = GetRequiredFeeRate(wallet);
      if (required_feerate > feerate_needed) {
          feerate_needed = required_feerate;
          if (feeCalc) feeCalc->reason = FeeReason::REQUIRED;
      }
      return feerate_needed;
  }
  
  CFeeRate GetDiscardRate(const CWallet& wallet)
  {
      unsigned int highest_target = wallet.chain().estimateMaxBlocks();
      CFeeRate discard_rate = wallet.chain().estimateSmartFee(highest_target, false /* conservative */);
      // Don't let discard_rate be greater than longest possible fee estimate if we get a valid fee estimate
      discard_rate = (discard_rate == CFeeRate(0)) ? wallet.m_discard_rate : std::min(discard_rate, wallet.m_discard_rate);
      // Discard rate must be at least dustRelayFee
      discard_rate = std::max(discard_rate, wallet.chain().relayDustFee());
      return discard_rate;
  }
  