// Copyright (c) 2009-2019 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "checkpoints.h"

#include "chainparams.h"
#include "main.h"
#include "uint256.h"

#include <stdint.h>

#include <boost/foreach.hpp>

namespace Checkpoints {

    /**
     * How many times we expect transactions after the last checkpoint to
     * be slower. This number is a compromise, as it can't be accurate for
     * every system. When reindexing from a fast disk with a slow CPU, it
     * can be up to 20, while when downloading from a slow network with a
     * fast multicore CPU, it won't be much higher than 1.
     */
    static const double SIGCHECK_VERIFICATION_FACTOR = 5.0;

    bool fEnabled = true;

    bool CheckBlock(int nHeight, const uint256& hash)
    {
        if (!fEnabled)
            return true;

        const MapCheckpoints& checkpoints = *Params().Checkpoints().mapCheckpoints;

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

    //! Guess how far we are in the verification process at the given block index
    double GuessVerificationProgress(CBlockIndex *pindex, bool fSigchecks) {
        if (pindex==NULL)
            return 0.0;

        int64_t nNow = time(NULL);

        double fSigcheckVerificationFactor = fSigchecks ? SIGCHECK_VERIFICATION_FACTOR : 1.0;
        double fWorkBefore = 0.0; // Amount of work done before pindex
        double fWorkAfter = 0.0;  // Amount of work left after pindex (estimated)
        // Work is defined as: 1.0 per transaction before the last checkpoint, and
        // fSigcheckVerificationFactor per transaction after.

        const CCheckpointData &data = Params().Checkpoints();

        if (pindex->nChainTx <= data.nTransactionsLastCheckpoint) {
            double nCheapBefore = pindex->nChainTx;
            double nCheapAfter = data.nTransactionsLastCheckpoint - pindex->nChainTx;
            double nExpensiveAfter = (nNow - data.nTimeLastCheckpoint)/86400.0*data.fTransactionsPerDay;
            fWorkBefore = nCheapBefore;
            fWorkAfter = nCheapAfter + nExpensiveAfter*fSigcheckVerificationFactor;
        } else {
            double nCheapBefore = data.nTransactionsLastCheckpoint;
            double nExpensiveBefore = pindex->nChainTx - data.nTransactionsLastCheckpoint;
            double nExpensiveAfter = (nNow - pindex->GetBlockTime())/86400.0*data.fTransactionsPerDay;
            fWorkBefore = nCheapBefore + nExpensiveBefore*fSigcheckVerificationFactor;
            fWorkAfter = nExpensiveAfter*fSigcheckVerificationFactor;
        }

        return fWorkBefore / (fWorkBefore + fWorkAfter);
    }

    int GetTotalBlocksEstimate()
    {
        if (!fEnabled)
            return 0;

        const MapCheckpoints& checkpoints = *Params().Checkpoints().mapCheckpoints;

        return checkpoints.rbegin()->first;
    }

    CBlockIndex* GetLastCheckpoint()
    {
        if (!fEnabled)
            return NULL;

        const MapCheckpoints& checkpoints = *Params().Checkpoints().mapCheckpoints;

        BOOST_REVERSE_FOREACH(const MapCheckpoints::value_type& i, checkpoints)
        {
            const uint256& hash = i.second;
            BlockMap::const_iterator t = mapBlockIndex.find(hash);
            if (t != mapBlockIndex.end())
                return t->second;
        }
        return NULL;
    }

} // namespace Checkpoints
