// Copyright (c) 2009-2010 Satoshi Nakamoto

// Copyright (c) 2009-present 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_POLICY_FEERATE_H

#define BITCOIN_POLICY_FEERATE_H

#include <consensus/amount.h>

#include <serialize.h>

#include <util/feefrac.h>

#include <util/fees.h>

#include <cstdint>

#include <string>

#include <type_traits>

const std::string CURRENCY_UNIT = "BTC"; // One formatted unit

const std::string CURRENCY_ATOM = "sat"; // One indivisible minimum value unit

enum class FeeRateFormat {

    BTC_KVB, //!< Use BTC/kvB fee rate unit

    SAT_VB,  //!< Use sat/vB fee rate unit

};

/**

 * Fee rate in satoshis per virtualbyte: CAmount / vB

 * the feerate is represented internally as FeeFrac

 */

class CFeeRate

{

private:

    /** Fee rate in sats/vB (satoshis per N virtualbytes) */

    FeePerVSize m_feerate;

public:

    /** Fee rate of 0 satoshis per 0 vB */

    CFeeRate() = default;

    template<std::integral I> // Disallow silent float -> int conversion

    explicit CFeeRate(const I m_feerate_kvb) : m_feerate(FeePerVSize(m_feerate_kvb, 1000)) {}

CFeeRate::CFeeRate<int>(int)

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    explicit CFeeRate(const I m_feerate_kvb) : m_feerate(FeePerVSize(m_feerate_kvb, 1000)) {}

CFeeRate::CFeeRate<long>(long)

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    explicit CFeeRate(const I m_feerate_kvb) : m_feerate(FeePerVSize(m_feerate_kvb, 1000)) {}

CFeeRate::CFeeRate<unsigned int>(unsigned int)

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    explicit CFeeRate(const I m_feerate_kvb) : m_feerate(FeePerVSize(m_feerate_kvb, 1000)) {}

CFeeRate::CFeeRate<long long>(long long)

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    explicit CFeeRate(const I m_feerate_kvb) : m_feerate(FeePerVSize(m_feerate_kvb, 1000)) {}

    /**

     * Construct a fee rate from a fee in satoshis and a vsize in vB.

     *

     * Passing any virtual_bytes less than or equal to 0 will result in 0 fee rate per 0 size.

     */

    CFeeRate(const CAmount& nFeePaid, int32_t virtual_bytes);

    /**

     * Return the fee in satoshis for the given vsize in vbytes.

     * If the calculated fee would have fractional satoshis, then the

     * returned fee will always be rounded up to the nearest satoshi.

     */

    CAmount GetFee(int32_t virtual_bytes) const;

    FeePerVSize GetFeePerVSize() const { return m_feerate; }

    /**

     * Return the fee in satoshis for a vsize of 1000 vbytes

     */

    CAmount GetFeePerK() const { return CAmount(m_feerate.EvaluateFeeDown(1000)); }

    friend std::weak_ordering operator<=>(const CFeeRate& a, const CFeeRate& b) noexcept

    {

        return FeeRateCompare(a.m_feerate, b.m_feerate);

    }

    friend bool operator==(const CFeeRate& a, const CFeeRate& b) noexcept

    {

        return FeeRateCompare(a.m_feerate, b.m_feerate) == std::weak_ordering::equivalent;

    }

    CFeeRate& operator+=(const CFeeRate& a) {

        m_feerate = FeePerVSize(GetFeePerK() + a.GetFeePerK(), 1000);

        return *this;

    }

    std::string ToString(FeeRateFormat fee_rate_format = FeeRateFormat::BTC_KVB) const;

    friend CFeeRate operator*(const CFeeRate& f, int a) { return CFeeRate(a * f.m_feerate.fee, f.m_feerate.size); }

    friend CFeeRate operator*(int a, const CFeeRate& f) { return CFeeRate(a * f.m_feerate.fee, f.m_feerate.size); }

    SERIALIZE_METHODS(CFeeRate, obj) { READWRITE(obj.m_feerate.fee, obj.m_feerate.size); }

};

#endif // BITCOIN_POLICY_FEERATE_H