// Copyright (c) 2009-2012 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "checkpoints.h"

#include "txdb.h"
#include "main.h"
#include "uint256.h"

namespace Checkpoints
{
    typedef std::map<int, uint256> MapCheckpoints;

    //
    // What makes a good checkpoint block?
    // + Is surrounded by blocks with reasonable timestamps
    //   (no blocks before with a timestamp after, none after with
    //    timestamp before)
    // + Contains no strange transactions
    //
    static MapCheckpoints mapCheckpoints = {
        {     0, hashGenesisBlockOfficial },
        {  2000, uint256("0x0000000000b5f20078bf46ebdf1500813bb6b2cb482065aa93b89e073b2c6467")},
        {  2101, uint256("0xd4ea1ac45b63c8162a7fc8033cec441db8d532ba988202849d7831e32fe2d059")},
        {  2847, uint256("0xb5015e2835f13fd3bb6135cff9b31ac33310c9b77d694bdb592b8680d98d018e")},
        {  3589, uint256("0xb12a2ca3db4e288cada98aa2139768532bd4474c49dd7b8158031032dac08d51")},
        {  3935, uint256("0xe16290c9757d1368b8d7c35de07d4f8f70c2c9f9c785b667df0c3bff85086ca6")},
        {  5703, uint256("0x587db07bb2172ad7db72c5fabc2518262a1b27f503f99417510b2c6fafa6557b")},
        {  9000, uint256("0x00000000019ef6b2f5e7c324c7d083ee94502305aabc7e9cd73a7fb2a57bb8db")},
        {  9001, uint256("0x6d5c6c5f201cc9e59659ee0da30d1430dc6bf3b12a8ff4c3864ab8d6286b0007")},
        {  9002, uint256("0xa1e20fb1d44688b763690cf74d6aefe859e4cc32981f9e3f2b2ae9702bbcf249")},
        { 10881, uint256("0x4b6554c45e1e6764a6f3c309c47baf53c9edd81f624e52b072518cd15da237e6")},
        { 17650, uint256("0x224940e1f986a202209b8e762728d1452ab45870c308abf84905674acf326a47")},
                // Recent finality pin (PoS era). Closes the long unchecked span from
                // 17650 to the live tip so stale-bootstrap / low-trust forks below
                // this height are rejected outright. Hash from the canonical chain.
                { 2205000, uint256("0x6bdd3c5e5a32e1dd9a70e705f1a28d1dd84929f89579bd2696d41bc87f39446f")},
                { 2206004, uint256("0xb34e8e6a7bb7f52167d81aaad4d26f87a876898fdd0fce860916fc1aaf9a2a46")},
                // Continuous finality pins: every 1000 blocks from 2206500 onward so the
                // gap between the last hardcoded checkpoint and the live tip stays bounded.
                // Without these, a fresh node syncing from zero (no snapshot) has 8,400+
                // unverified blocks at tip — a peer feeding fork blocks at those heights
                // could trick an IBD node into accepting a divergent chain. With these
                // pins, any divergence >1000 blocks is rejected at AcceptBlock time.
                // All hashes verified against the canonical chain on 2026-07-01.
                { 2206500, uint256("0x707ea288242227e9b36ceeeecd5a16a6c918f8b6f7e6375128cba908ebfcbf27")},
                { 2207000, uint256("0x7af1cc23fdffb3a9ed2eb9aa5a8697e8af2f98c67c4f6baa9f4d7899cbfaf4ca")},
                { 2210000, uint256("0xe2dc2e55c6e1b3d2ea9d8a1f2b274bf64053ddd6a61335dc6896aa9c056956be")},
                { 2211000, uint256("0x61c8a179c928a1f0bbffa029b4f1aea67b04a98227a6d02e6137280404ed29dc")},
                { 2212000, uint256("0xf4df2b5d0d1de326b97ed5a3eeefef307a51791e03af401373e142f00453a9a8")},
                { 2213000, uint256("0x7bc9652d423676c52ba8b0a287e0b46e1eca6e8eecc51d3f30e0d665d3b236f5")},
                { 2214000, uint256("0x17e61ceb45db36358aaabe91b094a77ecba32370a467185fa9af75eef6c8e414")},
                { 2214400, uint256("0x8ebb818f7280850c5a3916b7c8a2bca603f7c4f9926d3cdc2262f726035d96ed")},
                // Post-rebuild finality pin (v6.2.5.0). Closes the gap between
                // the last hardcoded checkpoint and the live tip after -rebuildutxo.
                // Hash from the canonical chain on DNS2 after fresh UTXO rebuild.
                { 2219922, uint256("0x9ed3e1d38317950927f37f2867e3fc29e239fc1f4c57b182f55c6e04b73b52ec")},
                // Live-tip finality pins (v6.2.6.0). Verified against DNS3 chain state
                // on 2026-08-04. Closes the 4,841-block unchecked span between the
                // last hardcoded pin (2,219,922) and the live tip (2,224,763).
                // All hashes verified against the canonical chain on DNS3 (running
                // v6.2.3.0-geb02f34) at block 2,224,763. Verification transcript
                // (DNS3 getblockhash output) is archived in the v6.2.6.0 release
                // notes on bootstrap.cryptographic-triangles.org.
//
// Note: the gap from 2,219,922 to 2,222,900 is 2,978 blocks (larger than the
                // 1,000-block standard spacing), because block 2,220,000 etc. were
                // not indexed in DNS3's local block index when this release was
                // prepared. The 2,222,900+ pins restore the 1,000-block spacing
                // guarantee from that point to the live tip.
                { 2222900, uint256("0xe104c29d6a6ff983d9a02a9854a86c221a1f400f0116cb255cee2b8d5c7ced9f")},
                { 2223000, uint256("0x41926ba6dc9147e361ffd1ffc1a0357d7d7b66550ed05864d1ae103c6332371a")},
                { 2223500, uint256("0x998e65941f200359ca0c1f53ea128c27f83111e8bbb1db38b7ed2ed7a48b8e32")},
                { 2223700, uint256("0x97d3a70d258c34429c15b430e654fa1270e4de635ecec3c72ace92a0d04679c3")},
                { 2224000, uint256("0x4dddc0b555266a1207fef70af17db9a7b14ab5e1d7cf27882ea35cc77923841f")},
                { 2224500, uint256("0xe0fea543829dd0e8c02b7c657468cff775c7993658c16c1feaf1418b4080ba27")},
                { 2224700, uint256("0x2a8ea5ef954adb707286bc468fdf43d8d99d23a1d15cf4f17a35d58dd51b0944")},
                { 2224750, uint256("0x0f117fe05befb6d8a93c6e45bc3b3d48889208e2785ba6a3d723c8ad7c9d649f")},
                { 2224763, uint256("0x9d3575ac5428e64911e698ba0a8f773954b17b214a044d4b244fa2ec83c06674")}, // live tip
            };

    // Published UTXO snapshot file SHA256, keyed by snapshot height.
    // Each entry binds height -> SHA256 of the canonical snapshot file produced by
    // UtxoSnapshot::DumpSnapshot at that height. Used by SnapshotNet to verify
    // P2P-delivered snapshots without trusting any peer.
    //
    // Maintainers: after producing a snapshot, sha256 the file and add an entry
    // here. The corresponding (height, blockhash) must already exist in
    // mapCheckpoints / mapCheckpointsTestnet.
    static std::map<int, uint256> mapSnapshotHashes = {
        { 2206004, uint256("0x1419282dae817315ee1b955543f6248233fe5800f5e8488734a0ece5bd6781ea")},
        { 2219922, uint256("0x6dd8d782a04bb8dc4ccd5e88a4bc7726fe26bdebaed96b79242de1e2949b6ee6")},
        // Live-tip snapshot (v6.2.6.0). Generated from DNS3 (Samihost) at the
        // canonical tip 2,224,763, blockhash 9d3575ac...06674. Verified against
        // the canonical chain on 2026-08-04.
        { 2224763, uint256("0xa7ea62ad4e158faf07973e5cd1539c1895154c4e28685a3eb7af458a001037b7")},
    };

    static std::map<int, uint256> mapSnapshotHashesTestnet = {
    };

    static MapCheckpoints mapCheckpointsTestnet = {
        {     0, hashGenesisBlockTestNet },
        {  2000, uint256("0x0000000000b5f20078bf46ebdf1500813bb6b2cb482065aa93b89e073b2c6467")},
        {  2101, uint256("0xd4ea1ac45b63c8162a7fc8033cec441db8d532ba988202849d7831e32fe2d059")},
        {  2847, uint256("0xb5015e2835f13fd3bb6135cff9b31ac33310c9b77d694bdb592b8680d98d018e")},
        {  3589, uint256("0xb12a2ca3db4e288cada98aa2139768532bd4474c49dd7b8158031032dac08d51")},
        {  3935, uint256("0xe16290c9757d1368b8d7c35de07d4f8f70c2c9f9c785b667df0c3bff85086ca6")},
        {  5703, uint256("0x587db07bb2172ad7db72c5fabc2518262a1b27f503f99417510b2c6fafa6557b")},
        {  9000, uint256("0x00000000019ef6b2f5e7c324c7d083ee94502305aabc7e9cd73a7fb2a57bb8db")},
        {  9001, uint256("0x6d5c6c5f201cc9e59659ee0da30d1430dc6bf3b12a8ff4c3864ab8d6286b0007")},
        {  9002, uint256("0xa1e20fb1d44688b763690cf74d6aefe859e4cc32981f9e3f2b2ae9702bbcf249")},
        { 10881, uint256("0x4b6554c45e1e6764a6f3c309c47baf53c9edd81f624e52b072518cd15da237e6")},
        { 17650, uint256("0x224940e1f986a202209b8e762728d1452ab45870c308abf84905674acf326a47")},
    };

    bool CheckHardened(int nHeight, const uint256& hash)
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);

        MapCheckpoints::const_iterator i = checkpoints.find(nHeight);
        if (i == checkpoints.end()) return true;
        return hash == i->second;
    }

    bool IsKnownCheckpoint(int nHeight, const uint256& hash)
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);
        MapCheckpoints::const_iterator i = checkpoints.find(nHeight);
        if (i == checkpoints.end()) return false;
        return hash == i->second;
    }

    int GetTotalBlocksEstimate()
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);

        return checkpoints.rbegin()->first;
    }

    int GetBestSnapshotHeight()
    {
        std::map<int, uint256>& snaps = (fTestNet ? mapSnapshotHashesTestnet : mapSnapshotHashes);
        if (snaps.empty()) return 0;
        return snaps.rbegin()->first;
    }

    bool GetSnapshotHash(int nHeight, uint256& fileHashOut)
    {
        std::map<int, uint256>& snaps = (fTestNet ? mapSnapshotHashesTestnet : mapSnapshotHashes);
        auto it = snaps.find(nHeight);
        if (it == snaps.end()) return false;
        fileHashOut = it->second;
        return true;
    }

    CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex)
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);

        for (auto it = checkpoints.rbegin(); it != checkpoints.rend(); ++it)
        {
            const uint256& hash = it->second;
            std::map<uint256, CBlockIndex*>::const_iterator t = mapBlockIndex.find(hash);
            if (t != mapBlockIndex.end())
                return t->second;
        }
        return nullptr;
    }

    // Independent of mapBlockIndex: returns the highest compiled checkpoint
    // height for the current network. Returns -1 if the compiled map is
    // empty (an unusual, but not impossible, configuration). Used as the
    // fail-closed reorg floor before pindexLastHardenedCheckpoint has been
    // resolved against the local block index (early IBD / reindex /
    // bootstrap before the checkpoint block has been downloaded).
    int GetLastCheckpointHeight()
    {
        MapCheckpoints& checkpoints = (fTestNet ? mapCheckpointsTestnet : mapCheckpoints);
        if (checkpoints.empty()) return -1;
        return checkpoints.rbegin()->first;
    }

    // triangles: synchronized checkpoint (centrally broadcasted)
    uint256 hashSyncCheckpoint = uint256("0x7e7a6e4dd5fe895106fca912dfbacaeaf2a89e76c6a588df8ff96e0e18b96021");
    uint256 hashPendingCheckpoint = uint256("0x7e7a6e4dd5fe895106fca912dfbacaeaf2a89e76c6a588df8ff96e0e18b96021");
    CSyncCheckpoint checkpointMessage;
    CSyncCheckpoint checkpointMessagePending;
    uint256 hashInvalidCheckpoint = 0;
    CCriticalSection cs_hashSyncCheckpoint;

    // triangles: get last synchronized checkpoint
    CBlockIndex* GetLastSyncCheckpoint()
    {
        LOCK(cs_hashSyncCheckpoint);
        if (!mapBlockIndex.count(hashSyncCheckpoint))
            error("GetSyncCheckpoint: block index missing for current sync-checkpoint %s", hashSyncCheckpoint.ToString().c_str());
        else
            return mapBlockIndex[hashSyncCheckpoint];
        return nullptr;
    }

    // triangles: only descendant of current sync-checkpoint is allowed
    bool ValidateSyncCheckpoint(uint256 hashCheckpoint)
    {
        if (!mapBlockIndex.count(hashSyncCheckpoint))
            return error("ValidateSyncCheckpoint: block index missing for current sync-checkpoint %s", hashSyncCheckpoint.ToString().c_str());
        if (!mapBlockIndex.count(hashCheckpoint))
            return error("ValidateSyncCheckpoint: block index missing for received sync-checkpoint %s", hashCheckpoint.ToString().c_str());

        CBlockIndex* pindexSyncCheckpoint = mapBlockIndex[hashSyncCheckpoint];
        CBlockIndex* pindexCheckpointRecv = mapBlockIndex[hashCheckpoint];

        if (pindexCheckpointRecv->nHeight <= pindexSyncCheckpoint->nHeight)
        {
            // Received an older checkpoint, trace back from current checkpoint
            // to the same height of the received checkpoint to verify
            // that current checkpoint should be a descendant block
            CBlockIndex* pindex = pindexSyncCheckpoint;
            while (pindex->nHeight > pindexCheckpointRecv->nHeight)
                if (!(pindex = pindex->pprev))
                    return error("ValidateSyncCheckpoint: pprev null - block index structure failure");
            if (pindex->GetBlockHash() != hashCheckpoint)
            {
                hashInvalidCheckpoint = hashCheckpoint;
                return error("ValidateSyncCheckpoint: new sync-checkpoint %s is conflicting with current sync-checkpoint %s", hashCheckpoint.ToString().c_str(), hashSyncCheckpoint.ToString().c_str());
            }
            return false; // ignore older checkpoint
        }

        // Received checkpoint should be a descendant block of the current
        // checkpoint. Trace back to the same height of current checkpoint
        // to verify.
        CBlockIndex* pindex = pindexCheckpointRecv;
        while (pindex->nHeight > pindexSyncCheckpoint->nHeight)
            if (!(pindex = pindex->pprev))
                return error("ValidateSyncCheckpoint: pprev2 null - block index structure failure");
        if (pindex->GetBlockHash() != hashSyncCheckpoint)
        {
            hashInvalidCheckpoint = hashCheckpoint;
            return error("ValidateSyncCheckpoint: new sync-checkpoint %s is not a descendant of current sync-checkpoint %s", hashCheckpoint.ToString().c_str(), hashSyncCheckpoint.ToString().c_str());
        }
        return true;
    }

    bool WriteSyncCheckpoint(const uint256& hashCheckpoint)
    {
        auto txdb_holder = MakeChainDB(); CTxDBBase& txdb = *txdb_holder;
        txdb.TxnBegin();
        if (!txdb.WriteSyncCheckpoint(hashCheckpoint))
        {
            txdb.TxnAbort();
            return error("WriteSyncCheckpoint(): failed to write to db sync checkpoint %s", hashCheckpoint.ToString().c_str());
        }
        if (!txdb.TxnCommit())
            return error("WriteSyncCheckpoint(): failed to commit to db sync checkpoint %s", hashCheckpoint.ToString().c_str());

        Checkpoints::hashSyncCheckpoint = hashCheckpoint;
        return true;
    }

    bool AcceptPendingSyncCheckpoint()
    {
        LOCK(cs_hashSyncCheckpoint);
        if (hashPendingCheckpoint != 0 && mapBlockIndex.count(hashPendingCheckpoint))
        {
            if (!ValidateSyncCheckpoint(hashPendingCheckpoint))
            {
                hashPendingCheckpoint = 0;
                checkpointMessagePending.SetNull();
                return false;
            }

            auto txdb_holder = MakeChainDB(); CTxDBBase& txdb = *txdb_holder;
            CBlockIndex* pindexCheckpoint = mapBlockIndex[hashPendingCheckpoint];
            if (!pindexCheckpoint->IsInMainChain())
            {
                CBlock block;
                if (!block.ReadFromDisk(pindexCheckpoint))
                    return error("AcceptPendingSyncCheckpoint: ReadFromDisk failed for sync checkpoint %s", hashPendingCheckpoint.ToString().c_str());
                if (!block.SetBestChain(txdb, pindexCheckpoint))
                {
                    hashInvalidCheckpoint = hashPendingCheckpoint;
                    return error("AcceptPendingSyncCheckpoint: SetBestChain failed for sync checkpoint %s", hashPendingCheckpoint.ToString().c_str());
                }
            }

            if (!WriteSyncCheckpoint(hashPendingCheckpoint))
                return error("AcceptPendingSyncCheckpoint(): failed to write sync checkpoint %s", hashPendingCheckpoint.ToString().c_str());
            hashPendingCheckpoint = 0;
            checkpointMessage = checkpointMessagePending;
            checkpointMessagePending.SetNull();
            printf("AcceptPendingSyncCheckpoint : sync-checkpoint at %s\n", hashSyncCheckpoint.ToString().c_str());
            // relay the checkpoint
            if (!checkpointMessage.IsNull())
            {
                for (CNode* pnode : vNodes)
                    checkpointMessage.RelayTo(pnode);
            }
            return true;
        }
        return false;
    }

    // Automatically select a suitable sync-checkpoint 
    uint256 AutoSelectSyncCheckpoint()
    {
        const CBlockIndex *pindex = pindexBest;
        // Search backward for a block within max span and maturity window
        while (pindex->pprev && (pindex->GetBlockTime() + CHECKPOINT_MAX_SPAN > pindexBest->GetBlockTime() || pindex->nHeight + 8 > pindexBest->nHeight))
            pindex = pindex->pprev;
        return pindex->GetBlockHash();
    }

    // Check against synchronized checkpoint
    // Disabled: master key removed in V5, no new sync checkpoints possible.
    // Always returns true to prevent stale DB-persisted checkpoints from blocking IBD.
    bool CheckSync(const uint256& hashBlock, const CBlockIndex* pindexPrev)
    {
        return true;
    }

    bool WantedByPendingSyncCheckpoint(uint256 hashBlock)
    {
        LOCK(cs_hashSyncCheckpoint);
        if (hashPendingCheckpoint == 0)
            return false;
        if (hashBlock == hashPendingCheckpoint)
            return true;
        if (mapOrphanBlocks.count(hashPendingCheckpoint)
            && hashBlock == WantedByOrphan(mapOrphanBlocks[hashPendingCheckpoint].get()))
            return true;
        return false;
    }

    // triangles: reset synchronized checkpoint to last hardened checkpoint
    bool ResetSyncCheckpoint()
    {
        LOCK(cs_hashSyncCheckpoint);
        const uint256& hash = mapCheckpoints.rbegin()->second;
        if (mapBlockIndex.count(hash) && !mapBlockIndex[hash]->IsInMainChain())
        {
            // checkpoint block accepted but not yet in main chain
            printf("ResetSyncCheckpoint: SetBestChain to hardened checkpoint %s\n", hash.ToString().c_str());
            auto txdb_holder = MakeChainDB(); CTxDBBase& txdb = *txdb_holder;
            CBlock block;
            if (!block.ReadFromDisk(mapBlockIndex[hash]))
                return error("ResetSyncCheckpoint: ReadFromDisk failed for hardened checkpoint %s", hash.ToString().c_str());
            if (!block.SetBestChain(txdb, mapBlockIndex[hash]))
            {
                return error("ResetSyncCheckpoint: SetBestChain failed for hardened checkpoint %s", hash.ToString().c_str());
            }
        }
        else if(!mapBlockIndex.count(hash))
        {
            // checkpoint block not yet accepted
            hashPendingCheckpoint = hash;
            checkpointMessagePending.SetNull();
            printf("ResetSyncCheckpoint: pending for sync-checkpoint %s\n", hashPendingCheckpoint.ToString().c_str());
        }

        for (auto it = mapCheckpoints.rbegin(); it != mapCheckpoints.rend(); ++it)
        {
            const uint256& hash = it->second;
            if (mapBlockIndex.count(hash) && mapBlockIndex[hash]->IsInMainChain())
            {
                if (!WriteSyncCheckpoint(hash))
                    return error("ResetSyncCheckpoint: failed to write sync checkpoint %s", hash.ToString().c_str());
                printf("ResetSyncCheckpoint: sync-checkpoint reset to %s\n", hashSyncCheckpoint.ToString().c_str());
                return true;
            }
        }

        return false;
    }

    void AskForPendingSyncCheckpoint(CNode* pfrom)
    {
        LOCK(cs_hashSyncCheckpoint);
        if (pfrom && hashPendingCheckpoint != 0 && (!mapBlockIndex.count(hashPendingCheckpoint)) && (!mapOrphanBlocks.count(hashPendingCheckpoint)))
            pfrom->AskFor(CInv(MSG_BLOCK, hashPendingCheckpoint));
    }

    bool SetCheckpointPrivKey(std::string strPrivKey)
    {
        (void)strPrivKey;
        return error("SetCheckpointPrivKey: synchronized checkpoints are disabled");
    }

    bool SendSyncCheckpoint(uint256 hashCheckpoint)
    {
        (void)hashCheckpoint;
        return error("SendSyncCheckpoint: synchronized checkpoints are disabled");
    }

    // Is the sync-checkpoint outside maturity window?
    bool IsMatureSyncCheckpoint()
    {
        LOCK(cs_hashSyncCheckpoint);
        if (!mapBlockIndex.count(hashSyncCheckpoint))
            return true; // no valid sync checkpoint, treat as mature
        const CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];
        return (nBestHeight >= pindexSync->nHeight + nCoinbaseMaturity ||
                pindexSync->GetBlockTime() + nStakeMinAge < GetAdjustedTime());
    }
}

// triangles: sync-checkpoint master key (DISABLED for decentralization - v5 hard fork)
const std::string CSyncCheckpoint::strMasterPubKey = "";

std::string CSyncCheckpoint::strMasterPrivKey = "";

// triangles: verify signature of sync-checkpoint message
// The master-key system is disabled. Reject these legacy messages instead of
// treating unsigned data as authenticated if a dispatcher is added later.
bool CSyncCheckpoint::CheckSignature()
{
    return error("CSyncCheckpoint::CheckSignature: synchronized checkpoints are disabled");
}

// triangles: process synchronized checkpoint
bool CSyncCheckpoint::ProcessSyncCheckpoint(CNode* pfrom)
{
    if (!CheckSignature())
        return false;

    LOCK(Checkpoints::cs_hashSyncCheckpoint);
    if (!mapBlockIndex.count(hashCheckpoint))
    {
        // We haven't received the checkpoint chain, keep the checkpoint as pending
        Checkpoints::hashPendingCheckpoint = hashCheckpoint;
        Checkpoints::checkpointMessagePending = *this;
        printf("ProcessSyncCheckpoint: pending for sync-checkpoint %s\n", hashCheckpoint.ToString().c_str());
        // Ask this guy to fill in what we're missing
        if (pfrom)
        {
            pfrom->PushGetBlocks(pindexBest, hashCheckpoint);
            // ask directly as well in case rejected earlier by duplicate
            // proof-of-stake because getblocks may not get it this time
            pfrom->AskFor(CInv(MSG_BLOCK, mapOrphanBlocks.count(hashCheckpoint)? WantedByOrphan(mapOrphanBlocks[hashCheckpoint].get()) : hashCheckpoint));
        }
        return false;
    }

    if (!Checkpoints::ValidateSyncCheckpoint(hashCheckpoint))
        return false;

    auto txdb_holder = MakeChainDB(); CTxDBBase& txdb = *txdb_holder;
    CBlockIndex* pindexCheckpoint = mapBlockIndex[hashCheckpoint];
    if (!pindexCheckpoint->IsInMainChain())
    {
        // checkpoint chain received but not yet main chain
        CBlock block;
        if (!block.ReadFromDisk(pindexCheckpoint))
            return error("ProcessSyncCheckpoint: ReadFromDisk failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
        if (!block.SetBestChain(txdb, pindexCheckpoint))
        {
            Checkpoints::hashInvalidCheckpoint = hashCheckpoint;
            return error("ProcessSyncCheckpoint: SetBestChain failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
        }
    }

    if (!Checkpoints::WriteSyncCheckpoint(hashCheckpoint))
        return error("ProcessSyncCheckpoint(): failed to write sync checkpoint %s", hashCheckpoint.ToString().c_str());
    Checkpoints::checkpointMessage = *this;
    Checkpoints::hashPendingCheckpoint = 0;
    Checkpoints::checkpointMessagePending.SetNull();
    printf("ProcessSyncCheckpoint: sync-checkpoint at %s\n", hashCheckpoint.ToString().c_str());
    return true;
}