// Copyright (c) 2009-2010 Satoshi Nakamoto

// 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_CHAIN_H

#define BITCOIN_CHAIN_H

#include <arith_uint256.h>

#include <consensus/params.h>

#include <flatfile.h>

#include <kernel/cs_main.h>

#include <primitives/block.h>

#include <serialize.h>

#include <sync.h>

#include <uint256.h>

#include <util/time.h>

#include <algorithm>

#include <cassert>

#include <cstdint>

#include <string>

#include <vector>

/**

 * Maximum amount of time that a block timestamp is allowed to exceed the

 * current time before the block will be accepted.

 */

static constexpr int64_t MAX_FUTURE_BLOCK_TIME = 2 * 60 * 60;

/**

 * Timestamp window used as a grace period by code that compares external

 * timestamps (such as timestamps passed to RPCs, or wallet key creation times)

 * to block timestamps. This should be set at least as high as

 * MAX_FUTURE_BLOCK_TIME.

 */

static constexpr int64_t TIMESTAMP_WINDOW = MAX_FUTURE_BLOCK_TIME;

/**

 * Maximum gap between node time and block time used

 * for the "Catching up..." mode in GUI.

 *

 * Ref: https://github.com/bitcoin/bitcoin/pull/1026

 */

static constexpr int64_t MAX_BLOCK_TIME_GAP = 90 * 60;

class CBlockFileInfo

{

public:

    unsigned int nBlocks{};      //!< number of blocks stored in file

    unsigned int nSize{};        //!< number of used bytes of block file

    unsigned int nUndoSize{};    //!< number of used bytes in the undo file

    unsigned int nHeightFirst{}; //!< lowest height of block in file

    unsigned int nHeightLast{};  //!< highest height of block in file

    uint64_t nTimeFirst{};       //!< earliest time of block in file

    uint64_t nTimeLast{};        //!< latest time of block in file

    SERIALIZE_METHODS(CBlockFileInfo, obj)

    {

        READWRITE(VARINT(obj.nBlocks));

        READWRITE(VARINT(obj.nSize));

        READWRITE(VARINT(obj.nUndoSize));

        READWRITE(VARINT(obj.nHeightFirst));

        READWRITE(VARINT(obj.nHeightLast));

        READWRITE(VARINT(obj.nTimeFirst));

        READWRITE(VARINT(obj.nTimeLast));

    }

Unexecuted instantiation: void CBlockFileInfo::SerializationOps<DataStream, CBlockFileInfo, ActionUnserialize>(CBlockFileInfo&, DataStream&, ActionUnserialize)

Unexecuted instantiation: void CBlockFileInfo::SerializationOps<DataStream, CBlockFileInfo const, ActionSerialize>(CBlockFileInfo const&, DataStream&, ActionSerialize)

    CBlockFileInfo() = default;

    std::string ToString() const;

    /** update statistics (does not update nSize) */

    void AddBlock(unsigned int nHeightIn, uint64_t nTimeIn)

    {

        if (nBlocks == 0 || nHeightFirst > nHeightIn)

  Branch (76:13): [True: 0, False: 0]
  Branch (76:29): [True: 0, False: 0]

            nHeightFirst = nHeightIn;

        if (nBlocks == 0 || nTimeFirst > nTimeIn)

  Branch (78:13): [True: 0, False: 0]
  Branch (78:29): [True: 0, False: 0]

            nTimeFirst = nTimeIn;

        nBlocks++;

        if (nHeightIn > nHeightLast)

  Branch (81:13): [True: 0, False: 0]

            nHeightLast = nHeightIn;

        if (nTimeIn > nTimeLast)

  Branch (83:13): [True: 0, False: 0]

            nTimeLast = nTimeIn;

    }

};

enum BlockStatus : uint32_t {

    //! Unused.

    BLOCK_VALID_UNKNOWN      =    0,

    //! Reserved (was BLOCK_VALID_HEADER).

    BLOCK_VALID_RESERVED     =    1,

    //! All parent headers found, difficulty matches, timestamp >= median previous, checkpoint. Implies all parents

    //! are also at least TREE.

    BLOCK_VALID_TREE         =    2,

    /**

     * Only first tx is coinbase, 2 <= coinbase input script length <= 100, transactions valid, no duplicate txids,

     * sigops, size, merkle root. Implies all parents are at least TREE but not necessarily TRANSACTIONS.

     *

     * If a block's validity is at least VALID_TRANSACTIONS, CBlockIndex::nTx will be set. If a block and all previous

     * blocks back to the genesis block or an assumeutxo snapshot block are at least VALID_TRANSACTIONS,

     * CBlockIndex::m_chain_tx_count will be set.

     */

    BLOCK_VALID_TRANSACTIONS =    3,

    //! Outputs do not overspend inputs, no double spends, coinbase output ok, no immature coinbase spends, BIP30.

    //! Implies all previous blocks back to the genesis block or an assumeutxo snapshot block are at least VALID_CHAIN.

    BLOCK_VALID_CHAIN        =    4,

    //! Scripts & signatures ok. Implies all previous blocks back to the genesis block or an assumeutxo snapshot block

    //! are at least VALID_SCRIPTS.

    BLOCK_VALID_SCRIPTS      =    5,

    //! All validity bits.

    BLOCK_VALID_MASK         =   BLOCK_VALID_RESERVED | BLOCK_VALID_TREE | BLOCK_VALID_TRANSACTIONS |

                                 BLOCK_VALID_CHAIN | BLOCK_VALID_SCRIPTS,

    BLOCK_HAVE_DATA          =    8, //!< full block available in blk*.dat

    BLOCK_HAVE_UNDO          =   16, //!< undo data available in rev*.dat

    BLOCK_HAVE_MASK          =   BLOCK_HAVE_DATA | BLOCK_HAVE_UNDO,

    BLOCK_FAILED_VALID       =   32, //!< stage after last reached validness failed

    BLOCK_FAILED_CHILD       =   64, //!< descends from failed block

    BLOCK_FAILED_MASK        =   BLOCK_FAILED_VALID | BLOCK_FAILED_CHILD,

    BLOCK_OPT_WITNESS        =   128, //!< block data in blk*.dat was received with a witness-enforcing client

    BLOCK_STATUS_RESERVED    =   256, //!< Unused flag that was previously set on assumeutxo snapshot blocks and their

                                      //!< ancestors before they were validated, and unset when they were validated.

};

/** The block chain is a tree shaped structure starting with the

 * genesis block at the root, with each block potentially having multiple

 * candidates to be the next block. A blockindex may have multiple pprev pointing

 * to it, but at most one of them can be part of the currently active branch.

 */

class CBlockIndex

{

public:

    //! pointer to the hash of the block, if any. Memory is owned by this CBlockIndex

    const uint256* phashBlock{nullptr};

    //! pointer to the index of the predecessor of this block

    CBlockIndex* pprev{nullptr};

    //! pointer to the index of some further predecessor of this block

    CBlockIndex* pskip{nullptr};

    //! height of the entry in the chain. The genesis block has height 0

    int nHeight{0};

    //! Which # file this block is stored in (blk?????.dat)

    int nFile GUARDED_BY(::cs_main){0};

    //! Byte offset within blk?????.dat where this block's data is stored

    unsigned int nDataPos GUARDED_BY(::cs_main){0};

    //! Byte offset within rev?????.dat where this block's undo data is stored

    unsigned int nUndoPos GUARDED_BY(::cs_main){0};

    //! (memory only) Total amount of work (expected number of hashes) in the chain up to and including this block

    arith_uint256 nChainWork{};

    //! Number of transactions in this block. This will be nonzero if the block

    //! reached the VALID_TRANSACTIONS level, and zero otherwise.

    //! Note: in a potential headers-first mode, this number cannot be relied upon

    unsigned int nTx{0};

    //! (memory only) Number of transactions in the chain up to and including this block.

    //! This value will be non-zero if this block and all previous blocks back

    //! to the genesis block or an assumeutxo snapshot block have reached the

    //! VALID_TRANSACTIONS level.

    uint64_t m_chain_tx_count{0};

    //! Verification status of this block. See enum BlockStatus

    //!

    //! Note: this value is modified to show BLOCK_OPT_WITNESS during UTXO snapshot

    //! load to avoid the block index being spuriously rewound.

    //! @sa NeedsRedownload

    //! @sa ActivateSnapshot

    uint32_t nStatus GUARDED_BY(::cs_main){0};

    //! block header

    int32_t nVersion{0};

    uint256 hashMerkleRoot{};

    uint32_t nTime{0};

    uint32_t nBits{0};

    uint32_t nNonce{0};

    //! (memory only) Sequential id assigned to distinguish order in which blocks are received.

    int32_t nSequenceId{0};

    //! (memory only) Maximum nTime in the chain up to and including this block.

    unsigned int nTimeMax{0};

    explicit CBlockIndex(const CBlockHeader& block)

        : nVersion{block.nVersion},

          hashMerkleRoot{block.hashMerkleRoot},

          nTime{block.nTime},

          nBits{block.nBits},

          nNonce{block.nNonce}

    {

    }

    FlatFilePos GetBlockPos() const EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        FlatFilePos ret;

        if (nStatus & BLOCK_HAVE_DATA) {

  Branch (212:13): [True: 0, False: 0]

            ret.nFile = nFile;

            ret.nPos = nDataPos;

        }

        return ret;

    }

    FlatFilePos GetUndoPos() const EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        FlatFilePos ret;

        if (nStatus & BLOCK_HAVE_UNDO) {

  Branch (223:13): [True: 0, False: 0]

            ret.nFile = nFile;

            ret.nPos = nUndoPos;

        }

        return ret;

    }

    CBlockHeader GetBlockHeader() const

    {

        CBlockHeader block;

        block.nVersion = nVersion;

        if (pprev)

  Branch (234:13): [True: 0, False: 8.73k]

            block.hashPrevBlock = pprev->GetBlockHash();

        block.hashMerkleRoot = hashMerkleRoot;

        block.nTime = nTime;

        block.nBits = nBits;

        block.nNonce = nNonce;

        return block;

    }

    uint256 GetBlockHash() const

    {

        assert(phashBlock != nullptr);

        return *phashBlock;

    }

    /**

     * Check whether this block and all previous blocks back to the genesis block or an assumeutxo snapshot block have

     * reached VALID_TRANSACTIONS and had transactions downloaded (and stored to disk) at some point.

     *

     * Does not imply the transactions are consensus-valid (ConnectTip might fail)

     * Does not imply the transactions are still stored on disk. (IsBlockPruned might return true)

     *

     * Note that this will be true for the snapshot base block, if one is loaded, since its m_chain_tx_count value will have

     * been set manually based on the related AssumeutxoData entry.

     */

    bool HaveNumChainTxs() const { return m_chain_tx_count != 0; }

    NodeSeconds Time() const

    {

        return NodeSeconds{std::chrono::seconds{nTime}};

    }

    int64_t GetBlockTime() const

    {

        return (int64_t)nTime;

    }

    int64_t GetBlockTimeMax() const

    {

        return (int64_t)nTimeMax;

    }

    static constexpr int nMedianTimeSpan = 11;

    int64_t GetMedianTimePast() const

    {

        int64_t pmedian[nMedianTimeSpan];

        int64_t* pbegin = &pmedian[nMedianTimeSpan];

        int64_t* pend = &pmedian[nMedianTimeSpan];

        const CBlockIndex* pindex = this;

        for (int i = 0; i < nMedianTimeSpan && pindex; i++, pindex = pindex->pprev)

  Branch (285:25): [True: 13.5k, False: 0]
  Branch (285:48): [True: 6.76k, False: 6.76k]

            *(--pbegin) = pindex->GetBlockTime();

        std::sort(pbegin, pend);

        return pbegin[(pend - pbegin) / 2];

    }

    std::string ToString() const;

    //! Check whether this block index entry is valid up to the passed validity level.

    bool IsValid(enum BlockStatus nUpTo = BLOCK_VALID_TRANSACTIONS) const

        EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        assert(!(nUpTo & ~BLOCK_VALID_MASK)); // Only validity flags allowed.

        if (nStatus & BLOCK_FAILED_MASK)

  Branch (300:13): [True: 0, False: 74]

            return false;

        return ((nStatus & BLOCK_VALID_MASK) >= nUpTo);

    }

    //! Raise the validity level of this block index entry.

    //! Returns true if the validity was changed.

    bool RaiseValidity(enum BlockStatus nUpTo) EXCLUSIVE_LOCKS_REQUIRED(::cs_main)

    {

        AssertLockHeld(::cs_main);

        assert(!(nUpTo & ~BLOCK_VALID_MASK)); // Only validity flags allowed.

        if (nStatus & BLOCK_FAILED_MASK) return false;

  Branch (311:13): [True: 0, False: 0]

        if ((nStatus & BLOCK_VALID_MASK) < nUpTo) {

  Branch (313:13): [True: 0, False: 0]

            nStatus = (nStatus & ~BLOCK_VALID_MASK) | nUpTo;

            return true;

        }

        return false;

    }

    //! Build the skiplist pointer for this entry.

    void BuildSkip();

    //! Efficiently find an ancestor of this block.

    CBlockIndex* GetAncestor(int height);

    const CBlockIndex* GetAncestor(int height) const;

    CBlockIndex() = default;

    ~CBlockIndex() = default;

protected:

    //! CBlockIndex should not allow public copy construction because equality

    //! comparison via pointer is very common throughout the codebase, making

    //! use of copy a footgun. Also, use of copies do not have the benefit

    //! of simplifying lifetime considerations due to attributes like pprev and

    //! pskip, which are at risk of becoming dangling pointers in a copied

    //! instance.

    //!

    //! We declare these protected instead of simply deleting them so that

    //! CDiskBlockIndex can reuse copy construction.

    CBlockIndex(const CBlockIndex&) = default;

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

    CBlockIndex(CBlockIndex&&) = delete;

    CBlockIndex& operator=(CBlockIndex&&) = delete;

};

arith_uint256 GetBlockProof(const CBlockIndex& block);

/** Return the time it would take to redo the work difference between from and to, assuming the current hashrate corresponds to the difficulty at tip, in seconds. */

int64_t GetBlockProofEquivalentTime(const CBlockIndex& to, const CBlockIndex& from, const CBlockIndex& tip, const Consensus::Params&);

/** Find the forking point between two chain tips. */

const CBlockIndex* LastCommonAncestor(const CBlockIndex* pa, const CBlockIndex* pb);

/** Used to marshal pointers into hashes for db storage. */

class CDiskBlockIndex : public CBlockIndex

{

    /** Historically CBlockLocator's version field has been written to disk

     * streams as the client version, but the value has never been used.

     *

     * Hard-code to the highest client version ever written.

     * SerParams can be used if the field requires any meaning in the future.

     **/

    static constexpr int DUMMY_VERSION = 259900;

public:

    uint256 hashPrev;

    CDiskBlockIndex()

    {

        hashPrev = uint256();

    }

    explicit CDiskBlockIndex(const CBlockIndex* pindex) : CBlockIndex(*pindex)

    {

        hashPrev = (pprev ? pprev->GetBlockHash() : uint256());

  Branch (374:21): [True: 0, False: 0]

    }

    SERIALIZE_METHODS(CDiskBlockIndex, obj)

    {

        LOCK(::cs_main);

        int _nVersion = DUMMY_VERSION;

        READWRITE(VARINT_MODE(_nVersion, VarIntMode::NONNEGATIVE_SIGNED));

        READWRITE(VARINT_MODE(obj.nHeight, VarIntMode::NONNEGATIVE_SIGNED));

        READWRITE(VARINT(obj.nStatus));

        READWRITE(VARINT(obj.nTx));

        if (obj.nStatus & (BLOCK_HAVE_DATA | BLOCK_HAVE_UNDO)) READWRITE(VARINT_MODE(obj.nFile, VarIntMode::NONNEGATIVE_SIGNED));

  Branch (386:13): [True: 0, False: 0]

  Branch (386:13): [True: 0, False: 0]

        if (obj.nStatus & BLOCK_HAVE_DATA) READWRITE(VARINT(obj.nDataPos));

  Branch (387:13): [True: 0, False: 0]

  Branch (387:13): [True: 0, False: 0]

        if (obj.nStatus & BLOCK_HAVE_UNDO) READWRITE(VARINT(obj.nUndoPos));

  Branch (388:13): [True: 0, False: 0]

  Branch (388:13): [True: 0, False: 0]

        // block header

        READWRITE(obj.nVersion);

        READWRITE(obj.hashPrev);

        READWRITE(obj.hashMerkleRoot);

        READWRITE(obj.nTime);

        READWRITE(obj.nBits);

        READWRITE(obj.nNonce);

    }

Unexecuted instantiation: void CDiskBlockIndex::SerializationOps<DataStream, CDiskBlockIndex, ActionUnserialize>(CDiskBlockIndex&, DataStream&, ActionUnserialize)

Unexecuted instantiation: void CDiskBlockIndex::SerializationOps<DataStream, CDiskBlockIndex const, ActionSerialize>(CDiskBlockIndex const&, DataStream&, ActionSerialize)

    uint256 ConstructBlockHash() const

    {

        CBlockHeader block;

        block.nVersion = nVersion;

        block.hashPrevBlock = hashPrev;

        block.hashMerkleRoot = hashMerkleRoot;

        block.nTime = nTime;

        block.nBits = nBits;

        block.nNonce = nNonce;

        return block.GetHash();

    }

    uint256 GetBlockHash() = delete;

    std::string ToString() = delete;

};

/** An in-memory indexed chain of blocks. */

class CChain

{

private:

    std::vector<CBlockIndex*> vChain;

public:

    CChain() = default;

    CChain(const CChain&) = delete;

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

    /** Returns the index entry for the genesis block of this chain, or nullptr if none. */

    CBlockIndex* Genesis() const

    {

        return vChain.size() > 0 ? vChain[0] : nullptr;

  Branch (429:16): [True: 13.6k, False: 0]

    }

    /** Returns the index entry for the tip of this chain, or nullptr if none. */

    CBlockIndex* Tip() const

    {

        return vChain.size() > 0 ? vChain[vChain.size() - 1] : nullptr;

  Branch (435:16): [True: 60.6k, False: 0]

    }

    /** Returns the index entry at a particular height in this chain, or nullptr if no such height exists. */

    CBlockIndex* operator[](int nHeight) const

    {

        if (nHeight < 0 || nHeight >= (int)vChain.size())

  Branch (441:13): [True: 0, False: 27.3k]
  Branch (441:28): [True: 6.84k, False: 20.5k]

            return nullptr;

        return vChain[nHeight];

    }

    /** Efficiently check whether a block is present in this chain. */

    bool Contains(const CBlockIndex* pindex) const

    {

        return (*this)[pindex->nHeight] == pindex;

    }

    /** Find the successor of a block in this chain, or nullptr if the given index is not found or is the tip. */

    CBlockIndex* Next(const CBlockIndex* pindex) const

    {

        if (Contains(pindex))

  Branch (455:13): [True: 0, False: 0]

            return (*this)[pindex->nHeight + 1];

        else

            return nullptr;

    }

    /** Return the maximal height in the chain. Is equal to chain.Tip() ? chain.Tip()->nHeight : -1. */

    int Height() const

    {

        return int(vChain.size()) - 1;

    }

    /** Set/initialize a chain with a given tip. */

    void SetTip(CBlockIndex& block);

    /** Return a CBlockLocator that refers to the tip in of this chain. */

    CBlockLocator GetLocator() const;

    /** Find the last common block between this chain and a block index entry. */

    const CBlockIndex* FindFork(const CBlockIndex* pindex) const;

    /** Find the earliest block with timestamp equal or greater than the given time and height equal or greater than the given height. */

    CBlockIndex* FindEarliestAtLeast(int64_t nTime, int height) const;

};

/** Get a locator for a block index entry. */

CBlockLocator GetLocator(const CBlockIndex* index);

/** Construct a list of hash entries to put in a locator.  */

std::vector<uint256> LocatorEntries(const CBlockIndex* index);

#endif // BITCOIN_CHAIN_H