text: // Copyright (c) 2017 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BITCOIN_WALLET_COINSELECTION_H
  #define BITCOIN_WALLET_COINSELECTION_H
  
  #include <amount.h>
  #include <primitives/transaction.h>
  #include <random.h>
  
  //! target minimum change amount
  static constexpr Amount MIN_CHANGE{COIN / 100};
  //! final minimum change amount after paying for fees
  static constexpr Amount MIN_FINAL_CHANGE = MIN_CHANGE / 2;
  
  class CInputCoin {
  public:
      CInputCoin(const CTransactionRef &tx, unsigned int i) {
          if (!tx) {
              throw std::invalid_argument("tx should not be null");
          }
          if (i >= tx->vout.size()) {
              throw std::out_of_range("The output index is out of range");
          }
  
          outpoint = COutPoint(tx->GetId(), i);
          txout = tx->vout[i];
          effective_value = txout.nValue;
      }
  
      CInputCoin(const CTransactionRef &tx, unsigned int i, int input_bytes)
          : CInputCoin(tx, i) {
          m_input_bytes = input_bytes;
      }
  
      COutPoint outpoint;
      CTxOut txout;
      Amount effective_value;
  
      /**
       * Pre-computed estimated size of this output as a fully-signed input in a
       * transaction. Can be -1 if it could not be calculated.
       */
      int m_input_bytes{-1};
  
      bool operator<(const CInputCoin &rhs) const {
          return outpoint < rhs.outpoint;
      }
  
      bool operator!=(const CInputCoin &rhs) const {
          return outpoint != rhs.outpoint;
      }
  
      bool operator==(const CInputCoin &rhs) const {
          return outpoint == rhs.outpoint;
      }
  };
  
  struct CoinEligibilityFilter {
      const int conf_mine;
      const int conf_theirs;
      const uint64_t max_ancestors;
      const uint64_t max_descendants;
  
      CoinEligibilityFilter(int conf_mine_, int conf_theirs_,
                            uint64_t max_ancestors_)
          : conf_mine(conf_mine_), conf_theirs(conf_theirs_),
            max_ancestors(max_ancestors_), max_descendants(max_ancestors_) {}
      CoinEligibilityFilter(int conf_mine_, int conf_theirs_,
                            uint64_t max_ancestors_, uint64_t max_descendants_)
          : conf_mine(conf_mine_), conf_theirs(conf_theirs_),
            max_ancestors(max_ancestors_), max_descendants(max_descendants_) {}
  };
  
  struct OutputGroup {
      std::vector<CInputCoin> m_outputs;
      bool m_from_me{true};
      Amount m_value = Amount::zero();
      int m_depth{999};
      size_t m_ancestors{0};
      size_t m_descendants{0};
      Amount effective_value = Amount::zero();
      Amount fee = Amount::zero();
      Amount long_term_fee = Amount::zero();
  
      OutputGroup() {}
      OutputGroup(std::vector<CInputCoin> &&outputs, bool from_me, Amount value,
                  int depth, size_t ancestors, size_t descendants)
          : m_outputs(std::move(outputs)), m_from_me(from_me), m_value(value),
            m_depth(depth), m_ancestors(ancestors), m_descendants(descendants) {}
      OutputGroup(const CInputCoin &output, int depth, bool from_me,
                  size_t ancestors, size_t descendants)
          : OutputGroup() {
          Insert(output, depth, from_me, ancestors, descendants);
      }
      void Insert(const CInputCoin &output, int depth, bool from_me,
                  size_t ancestors, size_t descendants);
      std::vector<CInputCoin>::iterator Discard(const CInputCoin &output);
      bool
      EligibleForSpending(const CoinEligibilityFilter &eligibility_filter) const;
  };
  
  bool SelectCoinsBnB(std::vector<OutputGroup> &utxo_pool,
                      const Amount &target_value, const Amount &cost_of_change,
                      std::set<CInputCoin> &out_set, Amount &value_ret,
                      const Amount not_input_fees);
  
  // Original coin selection algorithm as a fallback
  bool KnapsackSolver(const Amount nTargetValue, std::vector<OutputGroup> &groups,
                      std::set<CInputCoin> &setCoinsRet, Amount &nValueRet);
  
  #endif // BITCOIN_WALLET_COINSELECTION_H
  