// 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_VALIDATION_H

#define BITCOIN_VALIDATION_H

#include <arith_uint256.h>

#include <attributes.h>

#include <chain.h>

#include <checkqueue.h>

#include <consensus/amount.h>

#include <cuckoocache.h>

#include <deploymentstatus.h>

#include <kernel/chain.h>

#include <kernel/chainparams.h>

#include <kernel/chainstatemanager_opts.h>

#include <kernel/cs_main.h> // IWYU pragma: export

#include <node/blockstorage.h>

#include <policy/feerate.h>

#include <policy/packages.h>

#include <policy/policy.h>

#include <script/script_error.h>

#include <script/sigcache.h>

#include <sync.h>

#include <txdb.h>

#include <txmempool.h> // For CTxMemPool::cs

#include <uint256.h>

#include <util/check.h>

#include <util/fs.h>

#include <util/hasher.h>

#include <util/result.h>

#include <util/translation.h>

#include <versionbits.h>

#include <atomic>

#include <map>

#include <memory>

#include <optional>

#include <set>

#include <span>

#include <stdint.h>

#include <string>

#include <type_traits>

#include <utility>

#include <vector>

class Chainstate;

class CTxMemPool;

class ChainstateManager;

struct ChainTxData;

class DisconnectedBlockTransactions;

struct PrecomputedTransactionData;

struct LockPoints;

struct AssumeutxoData;

namespace node {

class SnapshotMetadata;

} // namespace node

namespace Consensus {

struct Params;

} // namespace Consensus

namespace util {

class SignalInterrupt;

} // namespace util

/** Block files containing a block-height within MIN_BLOCKS_TO_KEEP of ActiveChain().Tip() will not be pruned. */

static const unsigned int MIN_BLOCKS_TO_KEEP = 288;

static const signed int DEFAULT_CHECKBLOCKS = 6;

static constexpr int DEFAULT_CHECKLEVEL{3};

// Require that user allocate at least 550 MiB for block & undo files (blk???.dat and rev???.dat)

// At 1MB per block, 288 blocks = 288MB.

// Add 15% for Undo data = 331MB

// Add 20% for Orphan block rate = 397MB

// We want the low water mark after pruning to be at least 397 MB and since we prune in

// full block file chunks, we need the high water mark which triggers the prune to be

// one 128MB block file + added 15% undo data = 147MB greater for a total of 545MB

// Setting the target to >= 550 MiB will make it likely we can respect the target.

static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024;

/** Maximum number of dedicated script-checking threads allowed */

static constexpr int MAX_SCRIPTCHECK_THREADS{15};

/** Current sync state passed to tip changed callbacks. */

enum class SynchronizationState {

    INIT_REINDEX,

    INIT_DOWNLOAD,

    POST_INIT

};

/** Documentation for argument 'checklevel'. */

extern const std::vector<std::string> CHECKLEVEL_DOC;

CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams);

bool FatalError(kernel::Notifications& notifications, BlockValidationState& state, const bilingual_str& message);

/** Prune block files up to a given height */

void PruneBlockFilesManual(Chainstate& active_chainstate, int nManualPruneHeight);

/**

* Validation result for a transaction evaluated by MemPoolAccept (single or package).

* Here are the expected fields and properties of a result depending on its ResultType, applicable to

* results returned from package evaluation:

*+---------------------------+----------------+-------------------+------------------+----------------+-------------------+

*| Field or property         |    VALID       |                 INVALID              |  MEMPOOL_ENTRY | DIFFERENT_WITNESS |

*|                           |                |--------------------------------------|                |                   |

*|                           |                | TX_RECONSIDERABLE |     Other        |                |                   |

*+---------------------------+----------------+-------------------+------------------+----------------+-------------------+

*| txid in mempool?          | yes            | no                | no*              | yes            | yes               |

*| wtxid in mempool?         | yes            | no                | no*              | yes            | no                |

*| m_state                   | yes, IsValid() | yes, IsInvalid()  | yes, IsInvalid() | yes, IsValid() | yes, IsValid()    |

*| m_vsize                   | yes            | no                | no               | yes            | no                |

*| m_base_fees               | yes            | no                | no               | yes            | no                |

*| m_effective_feerate       | yes            | yes               | no               | no             | no                |

*| m_wtxids_fee_calculations | yes            | yes               | no               | no             | no                |

*| m_other_wtxid             | no             | no                | no               | no             | yes               |

*+---------------------------+----------------+-------------------+------------------+----------------+-------------------+

* (*) Individual transaction acceptance doesn't return MEMPOOL_ENTRY and DIFFERENT_WITNESS. It returns

* INVALID, with the errors txn-already-in-mempool and txn-same-nonwitness-data-in-mempool

* respectively. In those cases, the txid or wtxid may be in the mempool for a TX_CONFLICT.

*/

struct MempoolAcceptResult {

    /** Used to indicate the results of mempool validation. */

    enum class ResultType {

        VALID, //!> Fully validated, valid.

        INVALID, //!> Invalid.

        MEMPOOL_ENTRY, //!> Valid, transaction was already in the mempool.

        DIFFERENT_WITNESS, //!> Not validated. A same-txid-different-witness tx (see m_other_wtxid) already exists in the mempool and was not replaced.

    };

    /** Result type. Present in all MempoolAcceptResults. */

    const ResultType m_result_type;

    /** Contains information about why the transaction failed. */

    const TxValidationState m_state;

    /** Mempool transactions replaced by the tx. */

    const std::list<CTransactionRef> m_replaced_transactions;

    /** Virtual size as used by the mempool, calculated using serialized size and sigops. */

    const std::optional<int64_t> m_vsize;

    /** Raw base fees in satoshis. */

    const std::optional<CAmount> m_base_fees;

    /** The feerate at which this transaction was considered. This includes any fee delta added

     * using prioritisetransaction (i.e. modified fees). If this transaction was submitted as a

     * package, this is the package feerate, which may also include its descendants and/or

     * ancestors (see m_wtxids_fee_calculations below).

     */

    const std::optional<CFeeRate> m_effective_feerate;

    /** Contains the wtxids of the transactions used for fee-related checks. Includes this

     * transaction's wtxid and may include others if this transaction was validated as part of a

     * package. This is not necessarily equivalent to the list of transactions passed to

     * ProcessNewPackage().

     * Only present when m_result_type = ResultType::VALID. */

    const std::optional<std::vector<Wtxid>> m_wtxids_fee_calculations;

    /** The wtxid of the transaction in the mempool which has the same txid but different witness. */

    const std::optional<Wtxid> m_other_wtxid;

    static MempoolAcceptResult Failure(TxValidationState state) {

        return MempoolAcceptResult(state);

    }

    static MempoolAcceptResult FeeFailure(TxValidationState state,

                                          CFeeRate effective_feerate,

                                          const std::vector<Wtxid>& wtxids_fee_calculations) {

        return MempoolAcceptResult(state, effective_feerate, wtxids_fee_calculations);

    }

    static MempoolAcceptResult Success(std::list<CTransactionRef>&& replaced_txns,

                                       int64_t vsize,

                                       CAmount fees,

                                       CFeeRate effective_feerate,

                                       const std::vector<Wtxid>& wtxids_fee_calculations) {

        return MempoolAcceptResult(std::move(replaced_txns), vsize, fees,

                                   effective_feerate, wtxids_fee_calculations);

    }

    static MempoolAcceptResult MempoolTx(int64_t vsize, CAmount fees) {

        return MempoolAcceptResult(vsize, fees);

    }

    static MempoolAcceptResult MempoolTxDifferentWitness(const Wtxid& other_wtxid) {

        return MempoolAcceptResult(other_wtxid);

    }

// Private constructors. Use static methods MempoolAcceptResult::Success, etc. to construct.

private:

    /** Constructor for failure case */

    explicit MempoolAcceptResult(TxValidationState state)

        : m_result_type(ResultType::INVALID), m_state(state) {

            Assume(!state.IsValid()); // Can be invalid or error

        }

    /** Constructor for success case */

    explicit MempoolAcceptResult(std::list<CTransactionRef>&& replaced_txns,

                                 int64_t vsize,

                                 CAmount fees,

                                 CFeeRate effective_feerate,

                                 const std::vector<Wtxid>& wtxids_fee_calculations)

        : m_result_type(ResultType::VALID),

        m_replaced_transactions(std::move(replaced_txns)),

        m_vsize{vsize},

        m_base_fees(fees),

        m_effective_feerate(effective_feerate),

        m_wtxids_fee_calculations(wtxids_fee_calculations) {}

    /** Constructor for fee-related failure case */

    explicit MempoolAcceptResult(TxValidationState state,

                                 CFeeRate effective_feerate,

                                 const std::vector<Wtxid>& wtxids_fee_calculations)

        : m_result_type(ResultType::INVALID),

        m_state(state),

        m_effective_feerate(effective_feerate),

        m_wtxids_fee_calculations(wtxids_fee_calculations) {}

    /** Constructor for already-in-mempool case. It wouldn't replace any transactions. */

    explicit MempoolAcceptResult(int64_t vsize, CAmount fees)

        : m_result_type(ResultType::MEMPOOL_ENTRY), m_vsize{vsize}, m_base_fees(fees) {}

    /** Constructor for witness-swapped case. */

    explicit MempoolAcceptResult(const Wtxid& other_wtxid)

        : m_result_type(ResultType::DIFFERENT_WITNESS), m_other_wtxid(other_wtxid) {}

};

/**

* Validation result for package mempool acceptance.

*/

struct PackageMempoolAcceptResult

{

    PackageValidationState m_state;

    /**

    * Map from wtxid to finished MempoolAcceptResults. The client is responsible

    * for keeping track of the transaction objects themselves. If a result is not

    * present, it means validation was unfinished for that transaction. If there

    * was a package-wide error (see result in m_state), m_tx_results will be empty.

    */

    std::map<Wtxid, MempoolAcceptResult> m_tx_results;

    explicit PackageMempoolAcceptResult(PackageValidationState state,

                                        std::map<Wtxid, MempoolAcceptResult>&& results)

        : m_state{state}, m_tx_results(std::move(results)) {}

    explicit PackageMempoolAcceptResult(PackageValidationState state, CFeeRate feerate,

                                        std::map<Wtxid, MempoolAcceptResult>&& results)

        : m_state{state}, m_tx_results(std::move(results)) {}

    /** Constructor to create a PackageMempoolAcceptResult from a single MempoolAcceptResult */

    explicit PackageMempoolAcceptResult(const Wtxid& wtxid, const MempoolAcceptResult& result)

        : m_tx_results{ {wtxid, result} } {}

};

/**

 * Try to add a transaction to the mempool. This is an internal function and is exposed only for testing.

 * Client code should use ChainstateManager::ProcessTransaction()

 *

 * @param[in]  active_chainstate  Reference to the active chainstate.

 * @param[in]  tx                 The transaction to submit for mempool acceptance.

 * @param[in]  accept_time        The timestamp for adding the transaction to the mempool.

 *                                It is also used to determine when the entry expires.

 * @param[in]  bypass_limits      When true, don't enforce mempool fee and capacity limits,

 *                                and set entry_sequence to zero.

 * @param[in]  test_accept        When true, run validation checks but don't submit to mempool.

 *

 * @returns a MempoolAcceptResult indicating whether the transaction was accepted/rejected with reason.

 */

MempoolAcceptResult AcceptToMemoryPool(Chainstate& active_chainstate, const CTransactionRef& tx,

                                       int64_t accept_time, bool bypass_limits, bool test_accept)

    EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/**

* Validate (and maybe submit) a package to the mempool. See doc/policy/packages.md for full details

* on package validation rules.

* @param[in]    test_accept         When true, run validation checks but don't submit to mempool.

* @param[in]    client_maxfeerate    If exceeded by an individual transaction, rest of (sub)package evaluation is aborted.

*                                   Only for sanity checks against local submission of transactions.

* @returns a PackageMempoolAcceptResult which includes a MempoolAcceptResult for each transaction.

* If a transaction fails, validation will exit early and some results may be missing. It is also

* possible for the package to be partially submitted.

*/

PackageMempoolAcceptResult ProcessNewPackage(Chainstate& active_chainstate, CTxMemPool& pool,

                                                   const Package& txns, bool test_accept, const std::optional<CFeeRate>& client_maxfeerate)

                                                   EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/* Mempool validation helper functions */

/**

 * Check if transaction will be final in the next block to be created.

 */

bool CheckFinalTxAtTip(const CBlockIndex& active_chain_tip, const CTransaction& tx) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

/**

 * Calculate LockPoints required to check if transaction will be BIP68 final in the next block

 * to be created on top of tip.

 *

 * @param[in]   tip             Chain tip for which tx sequence locks are calculated. For

 *                              example, the tip of the current active chain.

 * @param[in]   coins_view      Any CCoinsView that provides access to the relevant coins for

 *                              checking sequence locks. For example, it can be a CCoinsViewCache

 *                              that isn't connected to anything but contains all the relevant

 *                              coins, or a CCoinsViewMemPool that is connected to the

 *                              mempool and chainstate UTXO set. In the latter case, the caller

 *                              is responsible for holding the appropriate locks to ensure that

 *                              calls to GetCoin() return correct coins.

 * @param[in]   tx              The transaction being evaluated.

 *

 * @returns The resulting height and time calculated and the hash of the block needed for

 *          calculation, or std::nullopt if there is an error.

 */

std::optional<LockPoints> CalculateLockPointsAtTip(

    CBlockIndex* tip,

    const CCoinsView& coins_view,

    const CTransaction& tx);

/**

 * Check if transaction will be BIP68 final in the next block to be created on top of tip.

 * @param[in]   tip             Chain tip to check tx sequence locks against. For example,

 *                              the tip of the current active chain.

 * @param[in]   lock_points     LockPoints containing the height and time at which this

 *                              transaction is final.

 * Simulates calling SequenceLocks() with data from the tip passed in.

 * The LockPoints should not be considered valid if CheckSequenceLocksAtTip returns false.

 */

bool CheckSequenceLocksAtTip(CBlockIndex* tip,

                             const LockPoints& lock_points);

/**

 * Closure representing one script verification

 * Note that this stores references to the spending transaction

 */

class CScriptCheck

{

private:

    CTxOut m_tx_out;

    const CTransaction *ptxTo;

    unsigned int nIn;

    unsigned int nFlags;

    bool cacheStore;

    PrecomputedTransactionData *txdata;

    SignatureCache* m_signature_cache;

public:

    CScriptCheck(const CTxOut& outIn, const CTransaction& txToIn, SignatureCache& signature_cache, unsigned int nInIn, unsigned int nFlagsIn, bool cacheIn, PrecomputedTransactionData* txdataIn) :

        m_tx_out(outIn), ptxTo(&txToIn), nIn(nInIn), nFlags(nFlagsIn), cacheStore(cacheIn), txdata(txdataIn), m_signature_cache(&signature_cache) { }

    CScriptCheck(const CScriptCheck&) = delete;

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

    CScriptCheck(CScriptCheck&&) = default;

    CScriptCheck& operator=(CScriptCheck&&) = default;

    std::optional<std::pair<ScriptError, std::string>> operator()();

};

// CScriptCheck is used a lot in std::vector, make sure that's efficient

static_assert(std::is_nothrow_move_assignable_v<CScriptCheck>);

static_assert(std::is_nothrow_move_constructible_v<CScriptCheck>);

static_assert(std::is_nothrow_destructible_v<CScriptCheck>);

/**

 * Convenience class for initializing and passing the script execution cache

 * and signature cache.

 */

class ValidationCache

{

private:

    //! Pre-initialized hasher to avoid having to recreate it for every hash calculation.

    CSHA256 m_script_execution_cache_hasher;

public:

    CuckooCache::cache<uint256, SignatureCacheHasher> m_script_execution_cache;

    SignatureCache m_signature_cache;

    ValidationCache(size_t script_execution_cache_bytes, size_t signature_cache_bytes);

    ValidationCache(const ValidationCache&) = delete;

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

    //! Return a copy of the pre-initialized hasher.

    CSHA256 ScriptExecutionCacheHasher() const { return m_script_execution_cache_hasher; }

};

/** Functions for validating blocks and updating the block tree */

/** Context-independent validity checks */

bool CheckBlock(const CBlock& block, BlockValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW = true, bool fCheckMerkleRoot = true);

/** Check a block is completely valid from start to finish (only works on top of our current best block) */

bool TestBlockValidity(BlockValidationState& state,

                       const CChainParams& chainparams,

                       Chainstate& chainstate,

                       const CBlock& block,

                       CBlockIndex* pindexPrev,

                       bool fCheckPOW = true,

                       bool fCheckMerkleRoot = true) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/** Check with the proof of work on each blockheader matches the value in nBits */

bool HasValidProofOfWork(const std::vector<CBlockHeader>& headers, const Consensus::Params& consensusParams);

/** Check if a block has been mutated (with respect to its merkle root and witness commitments). */

bool IsBlockMutated(const CBlock& block, bool check_witness_root);

/** Return the sum of the claimed work on a given set of headers. No verification of PoW is done. */

arith_uint256 CalculateClaimedHeadersWork(std::span<const CBlockHeader> headers);

enum class VerifyDBResult {

    SUCCESS,

    CORRUPTED_BLOCK_DB,

    INTERRUPTED,

    SKIPPED_L3_CHECKS,

    SKIPPED_MISSING_BLOCKS,

};

/** RAII wrapper for VerifyDB: Verify consistency of the block and coin databases */

class CVerifyDB

{

private:

    kernel::Notifications& m_notifications;

public:

    explicit CVerifyDB(kernel::Notifications& notifications);

    ~CVerifyDB();

    [[nodiscard]] VerifyDBResult VerifyDB(

        Chainstate& chainstate,

        const Consensus::Params& consensus_params,

        CCoinsView& coinsview,

        int nCheckLevel,

        int nCheckDepth) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

};

enum DisconnectResult

{

    DISCONNECT_OK,      // All good.

    DISCONNECT_UNCLEAN, // Rolled back, but UTXO set was inconsistent with block.

    DISCONNECT_FAILED   // Something else went wrong.

};

class ConnectTrace;

/** @see Chainstate::FlushStateToDisk */

enum class FlushStateMode {

    NONE,

    IF_NEEDED,

    PERIODIC,

    ALWAYS

};

/**

 * A convenience class for constructing the CCoinsView* hierarchy used

 * to facilitate access to the UTXO set.

 *

 * This class consists of an arrangement of layered CCoinsView objects,

 * preferring to store and retrieve coins in memory via `m_cacheview` but

 * ultimately falling back on cache misses to the canonical store of UTXOs on

 * disk, `m_dbview`.

 */

class CoinsViews {

public:

    //! The lowest level of the CoinsViews cache hierarchy sits in a leveldb database on disk.

    //! All unspent coins reside in this store.

    CCoinsViewDB m_dbview GUARDED_BY(cs_main);

    //! This view wraps access to the leveldb instance and handles read errors gracefully.

    CCoinsViewErrorCatcher m_catcherview GUARDED_BY(cs_main);

    //! This is the top layer of the cache hierarchy - it keeps as many coins in memory as

    //! can fit per the dbcache setting.

    std::unique_ptr<CCoinsViewCache> m_cacheview GUARDED_BY(cs_main);

    //! This constructor initializes CCoinsViewDB and CCoinsViewErrorCatcher instances, but it

    //! *does not* create a CCoinsViewCache instance by default. This is done separately because the

    //! presence of the cache has implications on whether or not we're allowed to flush the cache's

    //! state to disk, which should not be done until the health of the database is verified.

    //!

    //! All arguments forwarded onto CCoinsViewDB.

    CoinsViews(DBParams db_params, CoinsViewOptions options);

    //! Initialize the CCoinsViewCache member.

    void InitCache() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

};

enum class CoinsCacheSizeState

{

    //! The coins cache is in immediate need of a flush.

    CRITICAL = 2,

    //! The cache is at >= 90% capacity.

    LARGE = 1,

    OK = 0

};

/**

 * Chainstate stores and provides an API to update our local knowledge of the

 * current best chain.

 *

 * Eventually, the API here is targeted at being exposed externally as a

 * consumable library, so any functions added must only call

 * other class member functions, pure functions in other parts of the consensus

 * library, callbacks via the validation interface, or read/write-to-disk

 * functions (eventually this will also be via callbacks).

 *

 * Anything that is contingent on the current tip of the chain is stored here,

 * whereas block information and metadata independent of the current tip is

 * kept in `BlockManager`.

 */

class Chainstate

{

protected:

    /**

     * The ChainState Mutex

     * A lock that must be held when modifying this ChainState - held in ActivateBestChain() and

     * InvalidateBlock()

     */

    Mutex m_chainstate_mutex;

    //! Optional mempool that is kept in sync with the chain.

    //! Only the active chainstate has a mempool.

    CTxMemPool* m_mempool;

    //! Manages the UTXO set, which is a reflection of the contents of `m_chain`.

    std::unique_ptr<CoinsViews> m_coins_views;

    //! This toggle exists for use when doing background validation for UTXO

    //! snapshots.

    //!

    //! In the expected case, it is set once the background validation chain reaches the

    //! same height as the base of the snapshot and its UTXO set is found to hash to

    //! the expected assumeutxo value. It signals that we should no longer connect

    //! blocks to the background chainstate. When set on the background validation

    //! chainstate, it signifies that we have fully validated the snapshot chainstate.

    //!

    //! In the unlikely case that the snapshot chainstate is found to be invalid, this

    //! is set to true on the snapshot chainstate.

    bool m_disabled GUARDED_BY(::cs_main) {false};

    //! Cached result of LookupBlockIndex(*m_from_snapshot_blockhash)

    const CBlockIndex* m_cached_snapshot_base GUARDED_BY(::cs_main) {nullptr};

public:

    //! Reference to a BlockManager instance which itself is shared across all

    //! Chainstate instances.

    node::BlockManager& m_blockman;

    //! The chainstate manager that owns this chainstate. The reference is

    //! necessary so that this instance can check whether it is the active

    //! chainstate within deeply nested method calls.

    ChainstateManager& m_chainman;

    explicit Chainstate(

        CTxMemPool* mempool,

        node::BlockManager& blockman,

        ChainstateManager& chainman,

        std::optional<uint256> from_snapshot_blockhash = std::nullopt);

    //! Return the current role of the chainstate. See `ChainstateManager`

    //! documentation for a description of the different types of chainstates.

    //!

    //! @sa ChainstateRole

    ChainstateRole GetRole() const EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    /**

     * Initialize the CoinsViews UTXO set database management data structures. The in-memory

     * cache is initialized separately.

     *

     * All parameters forwarded to CoinsViews.

     */

    void InitCoinsDB(

        size_t cache_size_bytes,

        bool in_memory,

        bool should_wipe,

        fs::path leveldb_name = "chainstate");

    //! Initialize the in-memory coins cache (to be done after the health of the on-disk database

    //! is verified).

    void InitCoinsCache(size_t cache_size_bytes) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    //! @returns whether or not the CoinsViews object has been fully initialized and we can

    //!          safely flush this object to disk.

    bool CanFlushToDisk() const EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        return m_coins_views && m_coins_views->m_cacheview;

    }

    //! The current chain of blockheaders we consult and build on.

    //! @see CChain, CBlockIndex.

    CChain m_chain;

    /**

     * The blockhash which is the base of the snapshot this chainstate was created from.

     *

     * std::nullopt if this chainstate was not created from a snapshot.

     */

    const std::optional<uint256> m_from_snapshot_blockhash;

    /**

     * The base of the snapshot this chainstate was created from.

     *

     * nullptr if this chainstate was not created from a snapshot.

     */

    const CBlockIndex* SnapshotBase() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    /**

     * The set of all CBlockIndex entries that have as much work as our current

     * tip or more, and transaction data needed to be validated (with

     * BLOCK_VALID_TRANSACTIONS for each block and its parents back to the

     * genesis block or an assumeutxo snapshot block). Entries may be failed,

     * though, and pruning nodes may be missing the data for the block.

     */

    std::set<CBlockIndex*, node::CBlockIndexWorkComparator> setBlockIndexCandidates;

    //! @returns A reference to the in-memory cache of the UTXO set.

    CCoinsViewCache& CoinsTip() EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        Assert(m_coins_views);

        return *Assert(m_coins_views->m_cacheview);

    }

    //! @returns A reference to the on-disk UTXO set database.

    CCoinsViewDB& CoinsDB() EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        return Assert(m_coins_views)->m_dbview;

    }

    //! @returns A pointer to the mempool.

    CTxMemPool* GetMempool()

    {

        return m_mempool;

    }

    //! @returns A reference to a wrapped view of the in-memory UTXO set that

    //!     handles disk read errors gracefully.

    CCoinsViewErrorCatcher& CoinsErrorCatcher() EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        return Assert(m_coins_views)->m_catcherview;

    }

    //! Destructs all objects related to accessing the UTXO set.

    void ResetCoinsViews() { m_coins_views.reset(); }

    //! Does this chainstate have a UTXO set attached?

    bool HasCoinsViews() const { return (bool)m_coins_views; }

    //! The cache size of the on-disk coins view.

    size_t m_coinsdb_cache_size_bytes{0};

    //! The cache size of the in-memory coins view.

    size_t m_coinstip_cache_size_bytes{0};

    //! Resize the CoinsViews caches dynamically and flush state to disk.

    //! @returns true unless an error occurred during the flush.

    bool ResizeCoinsCaches(size_t coinstip_size, size_t coinsdb_size)

        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    /**

     * Update the on-disk chain state.

     * The caches and indexes are flushed depending on the mode we're called with

     * if they're too large, if it's been a while since the last write,

     * or always and in all cases if we're in prune mode and are deleting files.

     *

     * If FlushStateMode::NONE is used, then FlushStateToDisk(...) won't do anything

     * besides checking if we need to prune.

     *

     * @returns true unless a system error occurred

     */

    bool FlushStateToDisk(

        BlockValidationState& state,

        FlushStateMode mode,

        int nManualPruneHeight = 0);

    //! Unconditionally flush all changes to disk.

    void ForceFlushStateToDisk();

    //! Prune blockfiles from the disk if necessary and then flush chainstate changes

    //! if we pruned.

    void PruneAndFlush();

    /**

     * Find the best known block, and make it the tip of the block chain. The

     * result is either failure or an activated best chain. pblock is either

     * nullptr or a pointer to a block that is already loaded (to avoid loading

     * it again from disk).

     *

     * ActivateBestChain is split into steps (see ActivateBestChainStep) so that

     * we avoid holding cs_main for an extended period of time; the length of this

     * call may be quite long during reindexing or a substantial reorg.

     *

     * May not be called with cs_main held. May not be called in a

     * validationinterface callback.

     *

     * Note that if this is called while a snapshot chainstate is active, and if

     * it is called on a background chainstate whose tip has reached the base block

     * of the snapshot, its execution will take *MINUTES* while it hashes the

     * background UTXO set to verify the assumeutxo value the snapshot was activated

     * with. `cs_main` will be held during this time.

     *

     * @returns true unless a system error occurred

     */

    bool ActivateBestChain(

        BlockValidationState& state,

        std::shared_ptr<const CBlock> pblock = nullptr)

        EXCLUSIVE_LOCKS_REQUIRED(!m_chainstate_mutex)

        LOCKS_EXCLUDED(::cs_main);

    // Block (dis)connection on a given view:

    DisconnectResult DisconnectBlock(const CBlock& block, const CBlockIndex* pindex, CCoinsViewCache& view)

        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    bool ConnectBlock(const CBlock& block, BlockValidationState& state, CBlockIndex* pindex,

                      CCoinsViewCache& view, bool fJustCheck = false) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    // Apply the effects of a block disconnection on the UTXO set.

    bool DisconnectTip(BlockValidationState& state, DisconnectedBlockTransactions* disconnectpool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_mempool->cs);

    // Manual block validity manipulation:

    /** Mark a block as precious and reorganize.

     *

     * May not be called in a validationinterface callback.

     */

    bool PreciousBlock(BlockValidationState& state, CBlockIndex* pindex)

        EXCLUSIVE_LOCKS_REQUIRED(!m_chainstate_mutex)

        LOCKS_EXCLUDED(::cs_main);

    /** Mark a block as invalid. */

    bool InvalidateBlock(BlockValidationState& state, CBlockIndex* pindex)

        EXCLUSIVE_LOCKS_REQUIRED(!m_chainstate_mutex)

        LOCKS_EXCLUDED(::cs_main);

    /** Set invalidity status to all descendants of a block */

    void SetBlockFailureFlags(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    /** Remove invalidity status from a block and its descendants. */

    void ResetBlockFailureFlags(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    /** Replay blocks that aren't fully applied to the database. */

    bool ReplayBlocks();

    /** Whether the chain state needs to be redownloaded due to lack of witness data */

    [[nodiscard]] bool NeedsRedownload() const EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    /** Ensures we have a genesis block in the block tree, possibly writing one to disk. */

    bool LoadGenesisBlock();

    void TryAddBlockIndexCandidate(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    void PruneBlockIndexCandidates();

    void ClearBlockIndexCandidates() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    /** Find the last common block of this chain and a locator. */

    const CBlockIndex* FindForkInGlobalIndex(const CBlockLocator& locator) const EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    /** Update the chain tip based on database information, i.e. CoinsTip()'s best block. */

    bool LoadChainTip() EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    //! Dictates whether we need to flush the cache to disk or not.

    //!

    //! @return the state of the size of the coins cache.

    CoinsCacheSizeState GetCoinsCacheSizeState() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    CoinsCacheSizeState GetCoinsCacheSizeState(

        size_t max_coins_cache_size_bytes,

        size_t max_mempool_size_bytes) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    std::string ToString() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    //! Indirection necessary to make lock annotations work with an optional mempool.

    RecursiveMutex* MempoolMutex() const LOCK_RETURNED(m_mempool->cs)

    {

        return m_mempool ? &m_mempool->cs : nullptr;

    }

private:

    bool ActivateBestChainStep(BlockValidationState& state, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_mempool->cs);

    bool ConnectTip(BlockValidationState& state, CBlockIndex* pindexNew, const std::shared_ptr<const CBlock>& pblock, ConnectTrace& connectTrace, DisconnectedBlockTransactions& disconnectpool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_mempool->cs);

    void InvalidBlockFound(CBlockIndex* pindex, const BlockValidationState& state) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    CBlockIndex* FindMostWorkChain() EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    bool RollforwardBlock(const CBlockIndex* pindex, CCoinsViewCache& inputs) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    void CheckForkWarningConditions() EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    void InvalidChainFound(CBlockIndex* pindexNew) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    /**

     * Make mempool consistent after a reorg, by re-adding or recursively erasing

     * disconnected block transactions from the mempool, and also removing any

     * other transactions from the mempool that are no longer valid given the new

     * tip/height.

     *

     * Note: we assume that disconnectpool only contains transactions that are NOT

     * confirmed in the current chain nor already in the mempool (otherwise,

     * in-mempool descendants of such transactions would be removed).

     *

     * Passing fAddToMempool=false will skip trying to add the transactions back,

     * and instead just erase from the mempool as needed.

     */

    void MaybeUpdateMempoolForReorg(

        DisconnectedBlockTransactions& disconnectpool,

        bool fAddToMempool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_mempool->cs);

    /** Check warning conditions and do some notifications on new chain tip set. */

    void UpdateTip(const CBlockIndex* pindexNew)

        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    SteadyClock::time_point m_last_write{};

    SteadyClock::time_point m_last_flush{};

    /**

     * In case of an invalid snapshot, rename the coins leveldb directory so

     * that it can be examined for issue diagnosis.

     */

    [[nodiscard]] util::Result<void> InvalidateCoinsDBOnDisk() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    friend ChainstateManager;

};

enum class SnapshotCompletionResult {

    SUCCESS,

    SKIPPED,

    // Expected assumeutxo configuration data is not found for the height of the

    // base block.

    MISSING_CHAINPARAMS,

    // Failed to generate UTXO statistics (to check UTXO set hash) for the background

    // chainstate.

    STATS_FAILED,

    // The UTXO set hash of the background validation chainstate does not match

    // the one expected by assumeutxo chainparams.

    HASH_MISMATCH,

    // The blockhash of the current tip of the background validation chainstate does

    // not match the one expected by the snapshot chainstate.

    BASE_BLOCKHASH_MISMATCH,

};

/**

 * Provides an interface for creating and interacting with one or two

 * chainstates: an IBD chainstate generated by downloading blocks, and

 * an optional snapshot chainstate loaded from a UTXO snapshot. Managed

 * chainstates can be maintained at different heights simultaneously.

 *

 * This class provides abstractions that allow the retrieval of the current

 * most-work chainstate ("Active") as well as chainstates which may be in

 * background use to validate UTXO snapshots.

 *

 * Definitions:

 *

 * *IBD chainstate*: a chainstate whose current state has been "fully"

 *   validated by the initial block download process.

 *

 * *Snapshot chainstate*: a chainstate populated by loading in an

 *    assumeutxo UTXO snapshot.

 *

 * *Active chainstate*: the chainstate containing the current most-work

 *    chain. Consulted by most parts of the system (net_processing,

 *    wallet) as a reflection of the current chain and UTXO set.

 *    This may either be an IBD chainstate or a snapshot chainstate.

 *

 * *Background IBD chainstate*: an IBD chainstate for which the

 *    IBD process is happening in the background while use of the

 *    active (snapshot) chainstate allows the rest of the system to function.

 */

class ChainstateManager

{

private:

    //! The chainstate used under normal operation (i.e. "regular" IBD) or, if

    //! a snapshot is in use, for background validation.

    //!

    //! Its contents (including on-disk data) will be deleted *upon shutdown*

    //! after background validation of the snapshot has completed. We do not

    //! free the chainstate contents immediately after it finishes validation

    //! to cautiously avoid a case where some other part of the system is still

    //! using this pointer (e.g. net_processing).

    //!

    //! Once this pointer is set to a corresponding chainstate, it will not

    //! be reset until init.cpp:Shutdown().

    //!

    //! It is important for the pointer to not be deleted until shutdown,

    //! because cs_main is not always held when the pointer is accessed, for

    //! example when calling ActivateBestChain, so there's no way you could

    //! prevent code from using the pointer while deleting it.

    std::unique_ptr<Chainstate> m_ibd_chainstate GUARDED_BY(::cs_main);

    //! A chainstate initialized on the basis of a UTXO snapshot. If this is

    //! non-null, it is always our active chainstate.

    //!

    //! Once this pointer is set to a corresponding chainstate, it will not

    //! be reset until init.cpp:Shutdown().

    //!

    //! It is important for the pointer to not be deleted until shutdown,

    //! because cs_main is not always held when the pointer is accessed, for

    //! example when calling ActivateBestChain, so there's no way you could

    //! prevent code from using the pointer while deleting it.

    std::unique_ptr<Chainstate> m_snapshot_chainstate GUARDED_BY(::cs_main);

    //! Points to either the ibd or snapshot chainstate; indicates our

    //! most-work chain.

    Chainstate* m_active_chainstate GUARDED_BY(::cs_main) {nullptr};

    CBlockIndex* m_best_invalid GUARDED_BY(::cs_main){nullptr};

    /** The last header for which a headerTip notification was issued. */

    CBlockIndex* m_last_notified_header GUARDED_BY(GetMutex()){nullptr};

    bool NotifyHeaderTip() LOCKS_EXCLUDED(GetMutex());

    //! Internal helper for ActivateSnapshot().

    //!

    //! De-serialization of a snapshot that is created with

    //! the dumptxoutset RPC.

    //! To reduce space the serialization format of the snapshot avoids

    //! duplication of tx hashes. The code takes advantage of the guarantee by

    //! leveldb that keys are lexicographically sorted.

    [[nodiscard]] util::Result<void> PopulateAndValidateSnapshot(

        Chainstate& snapshot_chainstate,

        AutoFile& coins_file,

        const node::SnapshotMetadata& metadata);

    /**

     * If a block header hasn't already been seen, call CheckBlockHeader on it, ensure

     * that it doesn't descend from an invalid block, and then add it to m_block_index.

     * Caller must set min_pow_checked=true in order to add a new header to the

     * block index (permanent memory storage), indicating that the header is

     * known to be part of a sufficiently high-work chain (anti-dos check).

     */

    bool AcceptBlockHeader(

        const CBlockHeader& block,

        BlockValidationState& state,

        CBlockIndex** ppindex,

        bool min_pow_checked) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    friend Chainstate;

    /** Most recent headers presync progress update, for rate-limiting. */

    MockableSteadyClock::time_point m_last_presync_update GUARDED_BY(GetMutex()){};

    std::array<ThresholdConditionCache, VERSIONBITS_NUM_BITS> m_warningcache GUARDED_BY(::cs_main);

    //! Return true if a chainstate is considered usable.

    //!

    //! This is false when a background validation chainstate has completed its

    //! validation of an assumed-valid chainstate, or when a snapshot

    //! chainstate has been found to be invalid.

    bool IsUsable(const Chainstate* const cs) const EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {

        return cs && !cs->m_disabled;

    }

    //! A queue for script verifications that have to be performed by worker threads.

    CCheckQueue<CScriptCheck> m_script_check_queue;

    //! Timers and counters used for benchmarking validation in both background

    //! and active chainstates.

    SteadyClock::duration GUARDED_BY(::cs_main) time_check{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_forks{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_connect{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_verify{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_undo{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_index{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_total{};

    int64_t GUARDED_BY(::cs_main) num_blocks_total{0};

    SteadyClock::duration GUARDED_BY(::cs_main) time_connect_total{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_flush{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_chainstate{};

    SteadyClock::duration GUARDED_BY(::cs_main) time_post_connect{};

public:

    using Options = kernel::ChainstateManagerOpts;

    explicit ChainstateManager(const util::SignalInterrupt& interrupt, Options options, node::BlockManager::Options blockman_options);

    //! Function to restart active indexes; set dynamically to avoid a circular

    //! dependency on `base/index.cpp`.

    std::function<void()> snapshot_download_completed = std::function<void()>();

    const CChainParams& GetParams() const { return m_options.chainparams; }

    const Consensus::Params& GetConsensus() const { return m_options.chainparams.GetConsensus(); }

    bool ShouldCheckBlockIndex() const;

    const arith_uint256& MinimumChainWork() const { return *Assert(m_options.minimum_chain_work); }

    const uint256& AssumedValidBlock() const { return *Assert(m_options.assumed_valid_block); }

    kernel::Notifications& GetNotifications() const { return m_options.notifications; };

    /**

     * Make various assertions about the state of the block index.

     *

     * By default this only executes fully when using the Regtest chain; see: m_options.check_block_index.

     */

    void CheckBlockIndex();

    /**

     * Alias for ::cs_main.

     * Should be used in new code to make it easier to make ::cs_main a member

     * of this class.

     * Generally, methods of this class should be annotated to require this

     * mutex. This will make calling code more verbose, but also help to:

     * - Clarify that the method will acquire a mutex that heavily affects

     *   overall performance.

     * - Force call sites to think how long they need to acquire the mutex to

     *   get consistent results.

     */

    RecursiveMutex& GetMutex() const LOCK_RETURNED(::cs_main) { return ::cs_main; }

    const util::SignalInterrupt& m_interrupt;

    const Options m_options;

    //! A single BlockManager instance is shared across each constructed

    //! chainstate to avoid duplicating block metadata.

    node::BlockManager m_blockman;

    ValidationCache m_validation_cache;

    /**

     * Whether initial block download has ended and IsInitialBlockDownload

     * should return false from now on.

     *

     * Mutable because we need to be able to mark IsInitialBlockDownload()

     * const, which latches this for caching purposes.

     */

    mutable std::atomic<bool> m_cached_finished_ibd{false};

    /**

     * Every received block is assigned a unique and increasing identifier, so we

     * know which one to give priority in case of a fork.

     */

    /** Blocks loaded from disk are assigned id 0, so start the counter at 1. */

    int32_t nBlockSequenceId GUARDED_BY(::cs_main) = 1;

    /** Decreasing counter (used by subsequent preciousblock calls). */

    int32_t nBlockReverseSequenceId = -1;

    /** chainwork for the last block that preciousblock has been applied to. */

    arith_uint256 nLastPreciousChainwork = 0;

    // Reset the memory-only sequence counters we use to track block arrival

    // (used by tests to reset state)

    void ResetBlockSequenceCounters() EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        nBlockSequenceId = 1;

        nBlockReverseSequenceId = -1;

    }

    /**

     * In order to efficiently track invalidity of headers, we keep the set of

     * blocks which we tried to connect and found to be invalid here (ie which

     * were set to BLOCK_FAILED_VALID since the last restart). We can then

     * walk this set and check if a new header is a descendant of something in

     * this set, preventing us from having to walk m_block_index when we try

     * to connect a bad block and fail.

     *

     * While this is more complicated than marking everything which descends

     * from an invalid block as invalid at the time we discover it to be

     * invalid, doing so would require walking all of m_block_index to find all

     * descendants. Since this case should be very rare, keeping track of all

     * BLOCK_FAILED_VALID blocks in a set should be just fine and work just as

     * well.

     *

     * Because we already walk m_block_index in height-order at startup, we go

     * ahead and mark descendants of invalid blocks as FAILED_CHILD at that time,

     * instead of putting things in this set.

     */

    std::set<CBlockIndex*> m_failed_blocks;

    /** Best header we've seen so far (used for getheaders queries' starting points). */

    CBlockIndex* m_best_header GUARDED_BY(::cs_main){nullptr};

    //! The total number of bytes available for us to use across all in-memory

    //! coins caches. This will be split somehow across chainstates.

    size_t m_total_coinstip_cache{0};

    //

    //! The total number of bytes available for us to use across all leveldb

    //! coins databases. This will be split somehow across chainstates.

    size_t m_total_coinsdb_cache{0};

    //! Instantiate a new chainstate.

    //!

    //! @param[in] mempool              The mempool to pass to the chainstate

    //                                  constructor

    Chainstate& InitializeChainstate(CTxMemPool* mempool) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    //! Get all chainstates currently being used.

    std::vector<Chainstate*> GetAll();

    //! Construct and activate a Chainstate on the basis of UTXO snapshot data.

    //!

    //! Steps:

    //!

    //! - Initialize an unused Chainstate.

    //! - Load its `CoinsViews` contents from `coins_file`.

    //! - Verify that the hash of the resulting coinsdb matches the expected hash

    //!   per assumeutxo chain parameters.

    //! - Wait for our headers chain to include the base block of the snapshot.

    //! - "Fast forward" the tip of the new chainstate to the base of the snapshot.

    //! - Move the new chainstate to `m_snapshot_chainstate` and make it our

    //!   ChainstateActive().

    [[nodiscard]] util::Result<CBlockIndex*> ActivateSnapshot(

        AutoFile& coins_file, const node::SnapshotMetadata& metadata, bool in_memory);

    //! Once the background validation chainstate has reached the height which

    //! is the base of the UTXO snapshot in use, compare its coins to ensure

    //! they match those expected by the snapshot.

    //!

    //! If the coins match (expected), then mark the validation chainstate for

    //! deletion and continue using the snapshot chainstate as active.

    //! Otherwise, revert to using the ibd chainstate and shutdown.

    SnapshotCompletionResult MaybeCompleteSnapshotValidation() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    //! Returns nullptr if no snapshot has been loaded.

    const CBlockIndex* GetSnapshotBaseBlock() const EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    //! The most-work chain.

    Chainstate& ActiveChainstate() const;