1// Copyright (c) 2009-2010 Satoshi Nakamoto
2// Copyright (c) 2009-present The Bitcoin Core developers
3// Distributed under the MIT software license, see the accompanying
4// file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6#ifndef BITCOIN_POLICY_FEERATE_H
7#define BITCOIN_POLICY_FEERATE_H
8
9#include <consensus/amount.h>
10#include <serialize.h>
11#include <util/feefrac.h>
12#include <util/fees.h>
13
14
15#include <cstdint>
16#include <string>
17#include <type_traits>
18
19inline const std::string CURRENCY_UNIT = "BTC"; // One formatted unit
20inline const std::string CURRENCY_ATOM = "sat"; // One indivisible minimum value unit
21
22enum class FeeRateFormat {
23    BTC_KVB, //!< Use BTC/kvB fee rate unit
24    SAT_VB,  //!< Use sat/vB fee rate unit
25};
26
27/**
28 * Fee rate in satoshis per virtualbyte: CAmount / vB
29 * the feerate is represented internally as FeeFrac
30 */
31class CFeeRate
32{
33private:
34    /** Fee rate in sats/vB (satoshis per N virtualbytes) */
35    FeePerVSize m_feerate;
36
37public:
38    /** Fee rate of 0 satoshis per 0 vB */
39    CFeeRate() = default;
40    template<std::integral I> // Disallow silent float -> int conversion
41    explicit constexpr CFeeRate(const I m_feerate_kvb) : m_feerate(FeePerVSize(m_feerate_kvb, 1000)) {}
42
43    /**
44     * Construct a fee rate from a fee in satoshis and a vsize in vB.
45     *
46     * Passing any virtual_bytes less than or equal to 0 will result in 0 fee rate per 0 size.
47     */
48    CFeeRate(const CAmount& nFeePaid, int32_t virtual_bytes);
49
50    /**
51     * Construct from a fee rate expressed as FeePerVSize.
52     *
53     * Lossless: CFeeRate is internally a FeePerVSize, so the exact
54     * fee/vsize fraction is preserved. A feerate whose size is less than
55     * or equal to 0 results in 0 fee rate per 0 size.
56     */
57    explicit CFeeRate(const FeePerVSize& feerate) : m_feerate{feerate.size > 0 ? feerate : FeePerVSize{}} {}
58
59    /**
60     * Return the fee in satoshis for the given vsize in vbytes.
61     * If the calculated fee would have fractional satoshis, then the
62     * returned fee will always be rounded up to the nearest satoshi.
63     */
64    CAmount GetFee(int32_t virtual_bytes) const;
65
66    FeePerVSize GetFeePerVSize() const { return m_feerate; }
67
68    /**
69     * Return the fee in satoshis for a vsize of 1000 vbytes
70     */
71    CAmount GetFeePerK() const { return CAmount(m_feerate.EvaluateFeeDown(1000)); }
72    friend std::strong_ordering operator<=>(const CFeeRate& a, const CFeeRate& b) noexcept
73    {
74        return ByRatio{a.m_feerate} <=> ByRatio{b.m_feerate};
75    }
76    friend bool operator==(const CFeeRate& a, const CFeeRate& b) noexcept
77    {
78        return ByRatio{a.m_feerate} == ByRatio{b.m_feerate};
79    }
80    CFeeRate& operator+=(const CFeeRate& a) {
81        m_feerate = FeePerVSize(GetFeePerK() + a.GetFeePerK(), 1000);
82        return *this;
83    }
84    std::string ToString(FeeRateFormat fee_rate_format = FeeRateFormat::BTC_KVB) const;
85    friend CFeeRate operator*(const CFeeRate& f, int a) { return CFeeRate(a * f.m_feerate.fee, f.m_feerate.size); }
86    friend CFeeRate operator*(int a, const CFeeRate& f) { return CFeeRate(a * f.m_feerate.fee, f.m_feerate.size); }
87
88    SERIALIZE_METHODS(CFeeRate, obj) { READWRITE(obj.m_feerate.fee, obj.m_feerate.size); }
89};
90
91#endif // BITCOIN_POLICY_FEERATE_H
92