// Copyright (c) 2009-2022 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_KERNEL_MEMPOOL_ENTRY_H

#define BITCOIN_KERNEL_MEMPOOL_ENTRY_H

#include <consensus/amount.h>

#include <consensus/validation.h>

#include <core_memusage.h>

#include <policy/policy.h>

#include <policy/settings.h>

#include <primitives/transaction.h>

#include <util/epochguard.h>

#include <util/overflow.h>

#include <chrono>

#include <functional>

#include <memory>

#include <set>

#include <stddef.h>

#include <stdint.h>

class CBlockIndex;

struct LockPoints {

    // Will be set to the blockchain height and median time past

    // values that would be necessary to satisfy all relative locktime

    // constraints (BIP68) of this tx given our view of block chain history

    int height{0};

    int64_t time{0};

    // As long as the current chain descends from the highest height block

    // containing one of the inputs used in the calculation, then the cached

    // values are still valid even after a reorg.

    CBlockIndex* maxInputBlock{nullptr};

};

struct CompareIteratorByHash {

    // SFINAE for T where T is either a pointer type (e.g., a txiter) or a reference_wrapper<T>

    // (e.g. a wrapped CTxMemPoolEntry&)

    template <typename T>

    bool operator()(const std::reference_wrapper<T>& a, const std::reference_wrapper<T>& b) const

    {

        return a.get().GetTx().GetHash() < b.get().GetTx().GetHash();

    }

    template <typename T>

    bool operator()(const T& a, const T& b) const

    {

        return a->GetTx().GetHash() < b->GetTx().GetHash();

    }

};

/** \class CTxMemPoolEntry

 *

 * CTxMemPoolEntry stores data about the corresponding transaction, as well

 * as data about all in-mempool transactions that depend on the transaction

 * ("descendant" transactions).

 *

 * When a new entry is added to the mempool, we update the descendant state

 * (m_count_with_descendants, nSizeWithDescendants, and nModFeesWithDescendants) for

 * all ancestors of the newly added transaction.

 *

 */

class CTxMemPoolEntry

{

public:

    typedef std::reference_wrapper<const CTxMemPoolEntry> CTxMemPoolEntryRef;

    // two aliases, should the types ever diverge

    typedef std::set<CTxMemPoolEntryRef, CompareIteratorByHash> Parents;

    typedef std::set<CTxMemPoolEntryRef, CompareIteratorByHash> Children;

private:

    CTxMemPoolEntry(const CTxMemPoolEntry&) = default;

    struct ExplicitCopyTag {

        explicit ExplicitCopyTag() = default;

    };

    const CTransactionRef tx;

    mutable Parents m_parents;

    mutable Children m_children;

    const CAmount nFee;             //!< Cached to avoid expensive parent-transaction lookups

    const int32_t nTxWeight;         //!< ... and avoid recomputing tx weight (also used for GetTxSize())

    const size_t nUsageSize;        //!< ... and total memory usage

    const int64_t nTime;            //!< Local time when entering the mempool

    const uint64_t entry_sequence;  //!< Sequence number used to determine whether this transaction is too recent for relay

    const unsigned int entryHeight; //!< Chain height when entering the mempool

    const bool spendsCoinbase;      //!< keep track of transactions that spend a coinbase

    const int64_t sigOpCost;        //!< Total sigop cost

    CAmount m_modified_fee;         //!< Used for determining the priority of the transaction for mining in a block

    mutable LockPoints lockPoints;  //!< Track the height and time at which tx was final

    // Information about descendants of this transaction that are in the

    // mempool; if we remove this transaction we must remove all of these

    // descendants as well.

    int64_t m_count_with_descendants{1}; //!< number of descendant transactions

    // Using int64_t instead of int32_t to avoid signed integer overflow issues.

    int64_t nSizeWithDescendants;      //!< ... and size

    CAmount nModFeesWithDescendants;   //!< ... and total fees (all including us)

    // Analogous statistics for ancestor transactions

    int64_t m_count_with_ancestors{1};

    // Using int64_t instead of int32_t to avoid signed integer overflow issues.

    int64_t nSizeWithAncestors;

    CAmount nModFeesWithAncestors;

    int64_t nSigOpCostWithAncestors;

public:

    CTxMemPoolEntry(const CTransactionRef& tx, CAmount fee,

                    int64_t time, unsigned int entry_height, uint64_t entry_sequence,

                    bool spends_coinbase,

                    int64_t sigops_cost, LockPoints lp)

        : tx{tx},

          nFee{fee},

          nTxWeight{GetTransactionWeight(*tx)},

          nUsageSize{RecursiveDynamicUsage(tx)},

          nTime{time},

          entry_sequence{entry_sequence},

          entryHeight{entry_height},

          spendsCoinbase{spends_coinbase},

          sigOpCost{sigops_cost},

          m_modified_fee{nFee},

          lockPoints{lp},

          nSizeWithDescendants{GetTxSize()},

          nModFeesWithDescendants{nFee},

          nSizeWithAncestors{GetTxSize()},

          nModFeesWithAncestors{nFee},

          nSigOpCostWithAncestors{sigOpCost} {}

    CTxMemPoolEntry(ExplicitCopyTag, const CTxMemPoolEntry& entry) : CTxMemPoolEntry(entry) {}

    CTxMemPoolEntry& operator=(const CTxMemPoolEntry&) = delete;

    CTxMemPoolEntry(CTxMemPoolEntry&&) = delete;

    CTxMemPoolEntry& operator=(CTxMemPoolEntry&&) = delete;

    static constexpr ExplicitCopyTag ExplicitCopy{};

    const CTransaction& GetTx() const { return *this->tx; }

    CTransactionRef GetSharedTx() const { return this->tx; }

    const CAmount& GetFee() const { return nFee; }

    int32_t GetTxSize() const

    {

        return GetVirtualTransactionSize(nTxWeight, sigOpCost, ::nBytesPerSigOp);

    }

    int32_t GetTxWeight() const { return nTxWeight; }

    std::chrono::seconds GetTime() const { return std::chrono::seconds{nTime}; }

    unsigned int GetHeight() const { return entryHeight; }

    uint64_t GetSequence() const { return entry_sequence; }

    int64_t GetSigOpCost() const { return sigOpCost; }

    CAmount GetModifiedFee() const { return m_modified_fee; }

    size_t DynamicMemoryUsage() const { return nUsageSize; }

    const LockPoints& GetLockPoints() const { return lockPoints; }

    // Adjusts the descendant state.

    void UpdateDescendantState(int32_t modifySize, CAmount modifyFee, int64_t modifyCount);

    // Adjusts the ancestor state

    void UpdateAncestorState(int32_t modifySize, CAmount modifyFee, int64_t modifyCount, int64_t modifySigOps);

    // Updates the modified fees with descendants/ancestors.

    void UpdateModifiedFee(CAmount fee_diff)

    {

        nModFeesWithDescendants = SaturatingAdd(nModFeesWithDescendants, fee_diff);

        nModFeesWithAncestors = SaturatingAdd(nModFeesWithAncestors, fee_diff);

        m_modified_fee = SaturatingAdd(m_modified_fee, fee_diff);

    }

    // Update the LockPoints after a reorg

    void UpdateLockPoints(const LockPoints& lp) const

    {

        lockPoints = lp;

    }

    uint64_t GetCountWithDescendants() const { return m_count_with_descendants; }

    int64_t GetSizeWithDescendants() const { return nSizeWithDescendants; }

    CAmount GetModFeesWithDescendants() const { return nModFeesWithDescendants; }

    bool GetSpendsCoinbase() const { return spendsCoinbase; }

    uint64_t GetCountWithAncestors() const { return m_count_with_ancestors; }

    int64_t GetSizeWithAncestors() const { return nSizeWithAncestors; }

    CAmount GetModFeesWithAncestors() const { return nModFeesWithAncestors; }

    int64_t GetSigOpCostWithAncestors() const { return nSigOpCostWithAncestors; }

    const Parents& GetMemPoolParentsConst() const { return m_parents; }

    const Children& GetMemPoolChildrenConst() const { return m_children; }

    Parents& GetMemPoolParents() const { return m_parents; }

    Children& GetMemPoolChildren() const { return m_children; }

    mutable size_t idx_randomized; //!< Index in mempool's txns_randomized

    mutable Epoch::Marker m_epoch_marker; //!< epoch when last touched, useful for graph algorithms

};

using CTxMemPoolEntryRef = CTxMemPoolEntry::CTxMemPoolEntryRef;

struct TransactionInfo {

    const CTransactionRef m_tx;

    /* The fee the transaction paid */

    const CAmount m_fee;

    /**

     * The virtual transaction size.

     *

     * This is a policy field which considers the sigop cost of the

     * transaction as well as its weight, and reinterprets it as bytes.

     *

     * It is the primary metric by which the mining algorithm selects

     * transactions.

     */

    const int64_t m_virtual_transaction_size;

    /* The block height the transaction entered the mempool */

    const unsigned int txHeight;

    TransactionInfo(const CTransactionRef& tx, const CAmount& fee, const int64_t vsize, const unsigned int height)

        : m_tx{tx},

          m_fee{fee},

          m_virtual_transaction_size{vsize},

          txHeight{height} {}

};

struct RemovedMempoolTransactionInfo {

    TransactionInfo info;

    explicit RemovedMempoolTransactionInfo(const CTxMemPoolEntry& entry)

        : info{entry.GetSharedTx(), entry.GetFee(), entry.GetTxSize(), entry.GetHeight()} {}

};

struct NewMempoolTransactionInfo {

    TransactionInfo info;

    /*

     * This boolean indicates whether the transaction was added

     * without enforcing mempool fee limits.

     */

    const bool m_mempool_limit_bypassed;

    /* This boolean indicates whether the transaction is part of a package. */

    const bool m_submitted_in_package;

    /*

     * This boolean indicates whether the blockchain is up to date when the

     * transaction is added to the mempool.

     */

    const bool m_chainstate_is_current;

    /* Indicates whether the transaction has unconfirmed parents. */

    const bool m_has_no_mempool_parents;

    explicit NewMempoolTransactionInfo(const CTransactionRef& tx, const CAmount& fee,

                                       const int64_t vsize, const unsigned int height,

                                       const bool mempool_limit_bypassed, const bool submitted_in_package,

                                       const bool chainstate_is_current,

                                       const bool has_no_mempool_parents)

        : info{tx, fee, vsize, height},

          m_mempool_limit_bypassed{mempool_limit_bypassed},

          m_submitted_in_package{submitted_in_package},

          m_chainstate_is_current{chainstate_is_current},

          m_has_no_mempool_parents{has_no_mempool_parents} {}

};

#endif // BITCOIN_KERNEL_MEMPOOL_ENTRY_H