// Copyright (c) 2009-2012 The Bitcoin developers
// Copyright (c) 2011-2012 The PPCoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <boost/assign/list_of.hpp> // for 'map_list_of()'
#include <boost/foreach.hpp>

#include "checkpoints.h"

#include "db.h"
#include "main.h"
#include "uint256.h"

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

    //
    // 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 =
        boost::assign::map_list_of
        ( 0, hashGenesisBlockOfficial )
        ; // ppcoin: no checkpoint yet; to be created in future releases

    bool CheckHardened(int nHeight, const uint256& hash)
    {
        if (fTestNet) return true; // Testnet has no checkpoints

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

    int GetTotalBlocksEstimate()
    {
        if (fTestNet) return 0;

        return mapCheckpoints.rbegin()->first;
    }

    CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex)
    {
        if (fTestNet) {
            std::map<uint256, CBlockIndex*>::const_iterator t = mapBlockIndex.find(hashGenesisBlock);
            if (t != mapBlockIndex.end())
                return t->second;
            return NULL;
        }

        BOOST_REVERSE_FOREACH(const MapCheckpoints::value_type& i, mapCheckpoints)
        {
            const uint256& hash = i.second;
            std::map<uint256, CBlockIndex*>::const_iterator t = mapBlockIndex.find(hash);
            if (t != mapBlockIndex.end())
                return t->second;
        }
        return NULL;
    }

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

    // ppcoin: 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 NULL;
    }

    // ppcoin: 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: pprev1 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)
    {
        CTxDB txdb;
        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());
        txdb.Close();

        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;
            }

            CTxDB txdb;
            CBlockIndex* pindexCheckpoint = mapBlockIndex[hashPendingCheckpoint];
            if (!pindexCheckpoint->IsInMainChain())
            {
                txdb.TxnBegin();
                if (!Reorganize(txdb, pindexCheckpoint))
                {
                    txdb.TxnAbort();
                    hashInvalidCheckpoint = hashPendingCheckpoint;
                    return error("ProcessSyncCheckpoint: Reorganize failed for sync checkpoint %s", hashPendingCheckpoint.ToString().c_str());
                }
            }
            txdb.Close();

            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())
            {
                BOOST_FOREACH(CNode* pnode, vNodes)
                    checkpointMessage.RelayTo(pnode);
            }
            return true;
        }
        return false;
    }

    uint256 AutoSelectSyncCheckpoint()
    {
        // select a block some time ago
        CBlockIndex *pindex = mapBlockIndex[hashSyncCheckpoint];
        while (pindex->pnext && pindex->pnext->GetBlockTime() + CHECKPOINT_MIN_SPAN <= GetAdjustedTime())
            pindex = pindex->pnext;
        return pindex->GetBlockHash();
    }

    // Check against synchronized checkpoint
    bool CheckSync(const uint256& hashBlock, const CBlockIndex* pindexPrev)
    {
        if (fTestNet) return true; // Testnet has no checkpoints
        int nHeight = pindexPrev->nHeight + 1;

        LOCK(cs_hashSyncCheckpoint);
        // sync-checkpoint should always be accepted block
        assert(mapBlockIndex.count(hashSyncCheckpoint));
        const CBlockIndex* pindexSync = mapBlockIndex[hashSyncCheckpoint];

        if (nHeight > pindexSync->nHeight)
        {
            // trace back to same height as sync-checkpoint
            const CBlockIndex* pindex = pindexPrev;
            while (pindex->nHeight > pindexSync->nHeight)
                if (!(pindex = pindex->pprev))
                    return error("CheckSync: pprev null - block index structure failure");
            if (pindex->nHeight < pindexSync->nHeight || pindex->GetBlockHash() != hashSyncCheckpoint)
                return false; // only descendant of sync-checkpoint can pass check
        }
        if (nHeight == pindexSync->nHeight && hashBlock != hashSyncCheckpoint)
            return false; // same height with sync-checkpoint
        if (nHeight < pindexSync->nHeight && !mapBlockIndex.count(hashBlock))
            return false; // lower height than sync-checkpoint
        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]))
            return true;
        return false;
    }

    // ppcoin: 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: Reorganize to hardened checkpoint %s\n", hash.ToString().c_str());
            CTxDB txdb;
            txdb.TxnBegin();
            if (!Reorganize(txdb, mapBlockIndex[hash]))
            {
                txdb.TxnAbort();
                return error("ResetSyncCheckpoint: Reorganize failed for hardened checkpoint %s", hash.ToString().c_str());
            }
            txdb.Close();
        }
        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());
        }

        BOOST_REVERSE_FOREACH(const MapCheckpoints::value_type& i, mapCheckpoints)
        {
            const uint256& hash = i.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));
    }
}

// ppcoin: sync-checkpoint master key
const std::string CSyncCheckpoint::strMasterPubKey = "0424f20205e5da98ba632bbd278a11a6499585f62bfb2c782377ef59f0251daab8085fc31471bcb8180bc75ed0fa41bb50c7c084511d54015a3a5241d645c7268a";

// ppcoin: verify signature of sync-checkpoint message
bool CSyncCheckpoint::CheckSignature()
{
    CKey key;
    if (!key.SetPubKey(ParseHex(CSyncCheckpoint::strMasterPubKey)))
        return error("CSyncCheckpoint::CheckSignature() : SetPubKey failed");
    if (!key.Verify(Hash(vchMsg.begin(), vchMsg.end()), vchSig))
        return error("CSyncCheckpoint::CheckSignature() : verify signature failed");

    // Now unserialize the data
    CDataStream sMsg(vchMsg, SER_NETWORK, PROTOCOL_VERSION);
    sMsg >> *(CUnsignedSyncCheckpoint*)this;
    return true;
}

// ppcoin: 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]) : hashCheckpoint));
        }
        return false;
    }

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

    CTxDB txdb;
    CBlockIndex* pindexCheckpoint = mapBlockIndex[hashCheckpoint];
    if (!pindexCheckpoint->IsInMainChain())
    {
        // checkpoint chain received but not yet main chain
        txdb.TxnBegin();
        if (!Reorganize(txdb, pindexCheckpoint))
        {
            txdb.TxnAbort();
            Checkpoints::hashInvalidCheckpoint = hashCheckpoint;
            return error("ProcessSyncCheckpoint: Reorganize failed for sync checkpoint %s", hashCheckpoint.ToString().c_str());
        }
    }
    txdb.Close();

    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;
}