// Copyright (c) 2009-2010 Satoshi Nakamoto
// 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 "chain.h"
#include "auxpow.h"
#include "txdb.h"

using namespace std;

/**
 * CChain implementation
 */
void CChain::SetTip(CBlockIndex *pindex) {
    if (pindex == NULL) {
        vChain.clear();
        return;
    }
    vChain.resize(pindex->nHeight + 1);
    while (pindex && vChain[pindex->nHeight] != pindex) {
        vChain[pindex->nHeight] = pindex;
        pindex = pindex->pprev;
    }
}

CBlockLocator CChain::GetLocator(const CBlockIndex *pindex) const {
    int nStep = 1;
    std::vector<uint256> vHave;
    vHave.reserve(32);

    if (!pindex)
        pindex = Tip();
    while (pindex) {
        vHave.push_back(pindex->GetBlockHash());
        // Stop when we have added the genesis block.
        if (pindex->nHeight == 0)
            break;
        // Exponentially larger steps back, plus the genesis block.
        int nHeight = std::max(pindex->nHeight - nStep, 0);
        if (Contains(pindex)) {
            // Use O(1) CChain index if possible.
            pindex = (*this)[nHeight];
        } else {
            // Otherwise, use O(log n) skiplist.
            pindex = pindex->GetAncestor(nHeight);
        }
        if (vHave.size() > 10)
            nStep *= 2;
    }

    return CBlockLocator(vHave);
}

const CBlockIndex *CChain::FindFork(const CBlockIndex *pindex) const {
    if (pindex->nHeight > Height())
        pindex = pindex->GetAncestor(Height());
    while (pindex && !Contains(pindex))
        pindex = pindex->pprev;
    return pindex;
}

std::string CDiskBlockIndex::ToString() const
{
    std::string str = "CDiskBlockIndex(";
    str += CBlockIndex::ToString();
    str += strprintf("\n                hashBlock=%s, hashPrev=%s, hashParentBlock=%s)",
        GetBlockHash().ToString(),
        hashPrev.ToString(),
        (auxpow.get() != NULL) ? auxpow->GetParentBlockHash().ToString() : "-");
    return str;
}

CBlockHeader CBlockIndex::GetBlockHeader(const std::map<uint256, boost::shared_ptr<CAuxPow> >& mapDirtyAuxPow) const
{
    CBlockHeader block;

    if (nVersion & BLOCK_VERSION_AUXPOW) {
        bool foundInDirty = false;
        {
            LOCK(cs_main);
            std::map<uint256, boost::shared_ptr<CAuxPow> >::const_iterator it = mapDirtyAuxPow.find(*phashBlock);
            if (it != mapDirtyAuxPow.end()) {
                block.auxpow = it->second;
                foundInDirty = true;
            }
        }
        if (!foundInDirty) {
            CDiskBlockIndex diskblockindex;
            // auxpow is not in memory, load CDiskBlockHeader
            // from database to get it

            pblocktree->ReadDiskBlockIndex(*phashBlock, diskblockindex);
            block.auxpow = diskblockindex.auxpow;
        }
    }

    block.nVersion       = nVersion;
    if (pprev)
        block.hashPrevBlock = pprev->GetBlockHash();
    block.hashMerkleRoot = hashMerkleRoot;
    block.nTime          = nTime;
    block.nBits          = nBits;
    block.nNonce         = nNonce;
    return block;
}
/** Turn the lowest '1' bit in the binary representation of a number into a '0'. */
int static inline InvertLowestOne(int n) { return n & (n - 1); }

/** Compute what height to jump back to with the CBlockIndex::pskip pointer. */
int static inline GetSkipHeight(int height) {
    if (height < 2)
        return 0;

    // Determine which height to jump back to. Any number strictly lower than height is acceptable,
    // but the following expression seems to perform well in simulations (max 110 steps to go back
    // up to 2**18 blocks).
    return (height & 1) ? InvertLowestOne(InvertLowestOne(height - 1)) + 1 : InvertLowestOne(height);
}

CBlockIndex* CBlockIndex::GetAncestor(int height)
{
    if (height > nHeight || height < 0)
        return NULL;

    CBlockIndex* pindexWalk = this;
    int heightWalk = nHeight;
    while (heightWalk > height) {
        int heightSkip = GetSkipHeight(heightWalk);
        int heightSkipPrev = GetSkipHeight(heightWalk - 1);
        if (heightSkip == height ||
            (heightSkip > height && !(heightSkipPrev < heightSkip - 2 &&
                                      heightSkipPrev >= height))) {
            // Only follow pskip if pprev->pskip isn't better than pskip->pprev.
            pindexWalk = pindexWalk->pskip;
            heightWalk = heightSkip;
        } else {
            pindexWalk = pindexWalk->pprev;
            heightWalk--;
        }
    }
    return pindexWalk;
}

const CBlockIndex* CBlockIndex::GetAncestor(int height) const
{
    return const_cast<CBlockIndex*>(this)->GetAncestor(height);
}

void CBlockIndex::BuildSkip()
{
    if (pprev)
        pskip = pprev->GetAncestor(GetSkipHeight(nHeight));
}
