// Copyright (c) 2012-2018 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 <coins.h>

#include <consensus/consensus.h>
#include <random.h>

bool CCoinsView::GetAnchorAt(const uint256 &rt, ZCIncrementalMerkleTree &tree) const { return false; }
bool CCoinsView::GetNullifier(const uint256 &nullifier) const { return false; }
bool CCoinsView::GetCoin(const COutPoint &outpoint, Coin &coin) const { return false; }
uint256 CCoinsView::GetBestBlock() const { return uint256(); }
uint256 CCoinsView::GetBestAnchor() const { return uint256(); };
std::vector<uint256> CCoinsView::GetHeadBlocks() const { return std::vector<uint256>(); }
bool CCoinsView::BatchWrite(CCoinsMap &mapCoins,
                            const uint256 &hashBlock,
                            const uint256 &hashAnchor,
                            CAnchorsMap &mapAnchors,
                            CNullifiersMap &mapNullifiers) { return false; }
CCoinsViewCursor *CCoinsView::Cursor() const { return nullptr; }

bool CCoinsView::HaveCoin(const COutPoint &outpoint) const
{
    Coin coin;
    return GetCoin(outpoint, coin);
}

CCoinsViewBacked::CCoinsViewBacked(CCoinsView *viewIn) : base(viewIn) { }
bool CCoinsViewBacked::GetAnchorAt(const uint256 &rt, ZCIncrementalMerkleTree &tree) const { return base->GetAnchorAt(rt, tree); }
bool CCoinsViewBacked::GetNullifier(const uint256 &nullifier) const { return base->GetNullifier(nullifier); }
bool CCoinsViewBacked::GetCoin(const COutPoint &outpoint, Coin &coin) const { return base->GetCoin(outpoint, coin); }
bool CCoinsViewBacked::HaveCoin(const COutPoint &outpoint) const { return base->HaveCoin(outpoint); }
uint256 CCoinsViewBacked::GetBestBlock() const { return base->GetBestBlock(); }
uint256 CCoinsViewBacked::GetBestAnchor() const { return base->GetBestAnchor(); }
std::vector<uint256> CCoinsViewBacked::GetHeadBlocks() const { return base->GetHeadBlocks(); }
void CCoinsViewBacked::SetBackend(CCoinsView &viewIn) { base = &viewIn; }
bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins,
                                  const uint256 &hashBlock,
                                  const uint256 &hashAnchor,
                                  CAnchorsMap &mapAnchors,
                                  CNullifiersMap &mapNullifiers) { return base->BatchWrite(mapCoins, hashBlock, hashAnchor, mapAnchors, mapNullifiers); }
CCoinsViewCursor *CCoinsViewBacked::Cursor() const { return base->Cursor(); }
size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }

SaltedOutpointHasher::SaltedOutpointHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}

SaltedUint256Hasher::SaltedUint256Hasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}


CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), cachedCoinsUsage(0) {}

size_t CCoinsViewCache::DynamicMemoryUsage() const {
    return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
}

CCoinsMap::iterator CCoinsViewCache::FetchCoin(const COutPoint &outpoint) const {
    CCoinsMap::iterator it = cacheCoins.find(outpoint);
    if (it != cacheCoins.end())
        return it;
    Coin tmp;
    if (!base->GetCoin(outpoint, tmp))
        return cacheCoins.end();
    CCoinsMap::iterator ret = cacheCoins.emplace(std::piecewise_construct, std::forward_as_tuple(outpoint), std::forward_as_tuple(std::move(tmp))).first;
    if (ret->second.coin.IsSpent()) {
        // The parent only has an empty entry for this outpoint; we can consider our
        // version as fresh.
        ret->second.flags = CCoinsCacheEntry::FRESH;
    }
    cachedCoinsUsage += ret->second.coin.DynamicMemoryUsage();
    return ret;
}

bool CCoinsViewCache::GetAnchorAt(const uint256 &rt, ZCIncrementalMerkleTree &tree) const {
    CAnchorsMap::const_iterator it = cacheAnchors.find(rt);
    if (it != cacheAnchors.end()) {
        if (it->second.entered) {
            tree = it->second.tree;
            return true;
        } else {
            return false;
        }
    }

    if (!base->GetAnchorAt(rt, tree)) {
        return false;
    }

    CAnchorsMap::iterator ret = cacheAnchors.insert(std::make_pair(rt, CAnchorsCacheEntry())).first;
    ret->second.entered = true;
    ret->second.tree = tree;
    cachedCoinsUsage += ret->second.tree.DynamicMemoryUsage();

    return true;
}

bool CCoinsViewCache::GetNullifier(const uint256 &nullifier) const {
    CNullifiersMap::iterator it = cacheNullifiers.find(nullifier);
    if (it != cacheNullifiers.end())
        return it->second.entered;

    CNullifiersCacheEntry entry;
    bool tmp = base->GetNullifier(nullifier);
    entry.entered = tmp;

    cacheNullifiers.insert(std::make_pair(nullifier, entry));

    return tmp;
}

void CCoinsViewCache::PushAnchor(const ZCIncrementalMerkleTree &tree) {
    uint256 newrt = tree.root();

    auto currentRoot = GetBestAnchor();

    // We don't want to overwrite an anchor we already have.
    // This occurs when a block doesn't modify mapAnchors at all,
    // because there are no joinsplits. We could get around this a
    // different way (make all blocks modify mapAnchors somehow)
    // but this is simpler to reason about.
    if (currentRoot != newrt) {
        auto insertRet = cacheAnchors.insert(std::make_pair(newrt, CAnchorsCacheEntry()));
        CAnchorsMap::iterator ret = insertRet.first;

        ret->second.entered = true;
        ret->second.tree = tree;
        ret->second.flags = CAnchorsCacheEntry::DIRTY;

        if (insertRet.second) {
            // An insert took place
            cachedCoinsUsage += ret->second.tree.DynamicMemoryUsage();
        }

        hashAnchor = newrt;
    }
}

void CCoinsViewCache::PopAnchor(const uint256 &newrt) {
    auto currentRoot = GetBestAnchor();

    // Blocks might not change the commitment tree, in which
    // case restoring the "old" anchor during a reorg must
    // have no effect.
    if (currentRoot != newrt) {
        // Bring the current best anchor into our local cache
        // so that its tree exists in memory.
        {
            ZCIncrementalMerkleTree tree;
            assert(GetAnchorAt(currentRoot, tree));
        }

        // Mark the anchor as unentered, removing it from view
        cacheAnchors[currentRoot].entered = false;

        // Mark the cache entry as dirty so it's propagated
        cacheAnchors[currentRoot].flags = CAnchorsCacheEntry::DIRTY;

        // Mark the new root as the best anchor
        hashAnchor = newrt;
    }
}

void CCoinsViewCache::SetNullifier(const uint256 &nullifier, bool spent) {
    std::pair<CNullifiersMap::iterator, bool> ret = cacheNullifiers.insert(std::make_pair(nullifier, CNullifiersCacheEntry()));
    ret.first->second.entered = spent;
    ret.first->second.flags |= CNullifiersCacheEntry::DIRTY;
}

bool CCoinsViewCache::GetCoin(const COutPoint &outpoint, Coin &coin) const {
    CCoinsMap::const_iterator it = FetchCoin(outpoint);
    if (it != cacheCoins.end()) {
        coin = it->second.coin;
        return !coin.IsSpent();
    }
    return false;
}

void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possible_overwrite) {
    assert(!coin.IsSpent());
    if (coin.out.scriptPubKey.IsUnspendable()) return;
    CCoinsMap::iterator it;
    bool inserted;
    std::tie(it, inserted) = cacheCoins.emplace(std::piecewise_construct, std::forward_as_tuple(outpoint), std::tuple<>());
    bool fresh = false;
    if (!inserted) {
        cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
    }
    if (!possible_overwrite) {
        if (!it->second.coin.IsSpent()) {
            throw std::logic_error("Adding new coin that replaces non-pruned entry");
        }
        fresh = !(it->second.flags & CCoinsCacheEntry::DIRTY);
    }
    it->second.coin = std::move(coin);
    it->second.flags |= CCoinsCacheEntry::DIRTY | (fresh ? CCoinsCacheEntry::FRESH : 0);
    cachedCoinsUsage += it->second.coin.DynamicMemoryUsage();
}

void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight, bool check) {
    bool fCoinbase = tx.IsCoinBase();
    const uint256& txid = tx.GetHash();
    for (size_t i = 0; i < tx.vout.size(); ++i) {
        bool overwrite = check ? cache.HaveCoin(COutPoint(txid, i)) : fCoinbase;
        // Always set the possible_overwrite flag to AddCoin for coinbase txn, in order to correctly
        // deal with the pre-BIP30 occurrences of duplicate coinbase transactions.
        cache.AddCoin(COutPoint(txid, i), Coin(tx.vout[i], nHeight, fCoinbase), overwrite);
    }
}

bool CCoinsViewCache::SpendCoin(const COutPoint &outpoint, Coin* moveout) {
    CCoinsMap::iterator it = FetchCoin(outpoint);
    if (it == cacheCoins.end()) return false;
    cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
    if (moveout) {
        *moveout = std::move(it->second.coin);
    }
    if (it->second.flags & CCoinsCacheEntry::FRESH) {
        cacheCoins.erase(it);
    } else {
        it->second.flags |= CCoinsCacheEntry::DIRTY;
        it->second.coin.Clear();
    }
    return true;
}

static const Coin coinEmpty;

const Coin& CCoinsViewCache::AccessCoin(const COutPoint &outpoint) const {
    CCoinsMap::const_iterator it = FetchCoin(outpoint);
    if (it == cacheCoins.end()) {
        return coinEmpty;
    } else {
        return it->second.coin;
    }
}

bool CCoinsViewCache::HaveCoin(const COutPoint &outpoint) const {
    CCoinsMap::const_iterator it = FetchCoin(outpoint);
    return (it != cacheCoins.end() && !it->second.coin.IsSpent());
}

bool CCoinsViewCache::HaveCoinInCache(const COutPoint &outpoint) const {
    CCoinsMap::const_iterator it = cacheCoins.find(outpoint);
    return (it != cacheCoins.end() && !it->second.coin.IsSpent());
}

uint256 CCoinsViewCache::GetBestBlock() const {
    if (hashBlock.IsNull())
        hashBlock = base->GetBestBlock();
    return hashBlock;
}

uint256 CCoinsViewCache::GetBestAnchor() const {
    if (hashAnchor.IsNull())
        hashAnchor = base->GetBestAnchor();
    return hashAnchor;
}

void CCoinsViewCache::SetBestBlock(const uint256 &hashBlockIn) {
    hashBlock = hashBlockIn;
}

bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins,
                                 const uint256 &hashBlockIn,
                                 const uint256 &hashAnchorIn,
                                 CAnchorsMap &mapAnchors,
                                 CNullifiersMap &mapNullifiers)
{
    for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end(); it = mapCoins.erase(it)) {
        // Ignore non-dirty entries (optimization).
        if (!(it->second.flags & CCoinsCacheEntry::DIRTY)) {
            continue;
        }
        CCoinsMap::iterator itUs = cacheCoins.find(it->first);
        if (itUs == cacheCoins.end()) {
            // The parent cache does not have an entry, while the child does
            // We can ignore it if it's both FRESH and pruned in the child
            if (!(it->second.flags & CCoinsCacheEntry::FRESH && it->second.coin.IsSpent())) {
                // Otherwise we will need to create it in the parent
                // and move the data up and mark it as dirty
                CCoinsCacheEntry& entry = cacheCoins[it->first];
                entry.coin = std::move(it->second.coin);
                cachedCoinsUsage += entry.coin.DynamicMemoryUsage();
                entry.flags = CCoinsCacheEntry::DIRTY;
                // We can mark it FRESH in the parent if it was FRESH in the child
                // Otherwise it might have just been flushed from the parent's cache
                // and already exist in the grandparent
                if (it->second.flags & CCoinsCacheEntry::FRESH) {
                    entry.flags |= CCoinsCacheEntry::FRESH;
                }
            }
        } else {
            // Assert that the child cache entry was not marked FRESH if the
            // parent cache entry has unspent outputs. If this ever happens,
            // it means the FRESH flag was misapplied and there is a logic
            // error in the calling code.
            if ((it->second.flags & CCoinsCacheEntry::FRESH) && !itUs->second.coin.IsSpent()) {
                throw std::logic_error("FRESH flag misapplied to cache entry for base transaction with spendable outputs");
            }

            // Found the entry in the parent cache
            if ((itUs->second.flags & CCoinsCacheEntry::FRESH) && it->second.coin.IsSpent()) {
                // The grandparent does not have an entry, and the child is
                // modified and being pruned. This means we can just delete
                // it from the parent.
                cachedCoinsUsage -= itUs->second.coin.DynamicMemoryUsage();
                cacheCoins.erase(itUs);
            } else {
                // A normal modification.
                cachedCoinsUsage -= itUs->second.coin.DynamicMemoryUsage();
                itUs->second.coin = std::move(it->second.coin);
                cachedCoinsUsage += itUs->second.coin.DynamicMemoryUsage();
                itUs->second.flags |= CCoinsCacheEntry::DIRTY;
                // NOTE: It is possible the child has a FRESH flag here in
                // the event the entry we found in the parent is pruned. But
                // we must not copy that FRESH flag to the parent as that
                // pruned state likely still needs to be communicated to the
                // grandparent.
            }
        }
    }

    for (CAnchorsMap::iterator child_it = mapAnchors.begin(); child_it != mapAnchors.end();)
    {
        if (child_it->second.flags & CAnchorsCacheEntry::DIRTY) {
            CAnchorsMap::iterator parent_it = cacheAnchors.find(child_it->first);

            if (parent_it == cacheAnchors.end()) {
                CAnchorsCacheEntry& entry = cacheAnchors[child_it->first];
                entry.entered = child_it->second.entered;
                entry.tree = child_it->second.tree;
                entry.flags = CAnchorsCacheEntry::DIRTY;

                cachedCoinsUsage += entry.tree.DynamicMemoryUsage();
            } else {
                if (parent_it->second.entered != child_it->second.entered) {
                    // The parent may have removed the entry.
                    parent_it->second.entered = child_it->second.entered;
                    parent_it->second.flags |= CAnchorsCacheEntry::DIRTY;
                }
            }
        }

        CAnchorsMap::iterator itOld = child_it++;
        mapAnchors.erase(itOld);
    }

    for (CNullifiersMap::iterator child_it = mapNullifiers.begin(); child_it != mapNullifiers.end();)
    {
        if (child_it->second.flags & CNullifiersCacheEntry::DIRTY) { // Ignore non-dirty entries (optimization).
            CNullifiersMap::iterator parent_it = cacheNullifiers.find(child_it->first);

            if (parent_it == cacheNullifiers.end()) {
                CNullifiersCacheEntry& entry = cacheNullifiers[child_it->first];
                entry.entered = child_it->second.entered;
                entry.flags = CNullifiersCacheEntry::DIRTY;
            } else {
                if (parent_it->second.entered != child_it->second.entered) {
                    parent_it->second.entered = child_it->second.entered;
                    parent_it->second.flags |= CNullifiersCacheEntry::DIRTY;
                }
            }
        }
        CNullifiersMap::iterator itOld = child_it++;
        mapNullifiers.erase(itOld);
    }

    hashAnchor = hashAnchorIn;
    hashBlock = hashBlockIn;
    return true;
}

bool CCoinsViewCache::Flush() {
    bool fOk = base->BatchWrite(cacheCoins, hashBlock, hashAnchor, cacheAnchors, cacheNullifiers);
    cacheCoins.clear();
    cacheAnchors.clear();
    cacheNullifiers.clear();
    cachedCoinsUsage = 0;
    return fOk;
}

void CCoinsViewCache::Uncache(const COutPoint& hash)
{
    CCoinsMap::iterator it = cacheCoins.find(hash);
    if (it != cacheCoins.end() && it->second.flags == 0) {
        cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
        cacheCoins.erase(it);
    }
}

unsigned int CCoinsViewCache::GetCacheSize() const {
    return cacheCoins.size();
}

CAmount CCoinsViewCache::GetValueIn(const CTransaction& tx) const
{
    if (tx.IsCoinBase())
        return 0;

    CAmount nResult = 0;
    for (unsigned int i = 0; i < tx.vin.size(); i++)
        nResult += AccessCoin(tx.vin[i].prevout).out.nValue;

    return nResult;
}

bool CCoinsViewCache::HaveJoinSplitRequirements(const CTransaction& tx) const
{
    std::unordered_map<uint256, ZCIncrementalMerkleTree, SaltedUint256Hasher> intermediates;

    for(const JSDescription &joinsplit : tx.vjoinsplit)
    {
        for(const uint256& nullifier : joinsplit.nullifiers)
        {
            if (GetNullifier(nullifier)) {
                // If the nullifier is set, this transaction
                // double-spends!
                return false;
            }
        }

        ZCIncrementalMerkleTree tree;
        auto it = intermediates.find(joinsplit.anchor);
        if (it != intermediates.end()) {
            tree = it->second;
        } else if (!GetAnchorAt(joinsplit.anchor, tree)) {
            return false;
        }

        for(const uint256& commitment : joinsplit.commitments)
        {
            tree.append(commitment);
        }

        intermediates.insert(std::make_pair(tree.root(), tree));
    }

    return true;
}

bool CCoinsViewCache::HaveInputs(const CTransaction& tx) const
{
    if (!tx.IsCoinBase()) {
        for (unsigned int i = 0; i < tx.vin.size(); i++) {
            if (!HaveCoin(tx.vin[i].prevout)) {
                return false;
            }
        }
    }
    return true;
}

static const size_t MIN_TRANSACTION_OUTPUT_WEIGHT = WITNESS_SCALE_FACTOR * ::GetSerializeSize(CTxOut(), PROTOCOL_VERSION);
static const size_t MAX_OUTPUTS_PER_BLOCK = MAX_BLOCK_WEIGHT / MIN_TRANSACTION_OUTPUT_WEIGHT;

const Coin& AccessByTxid(const CCoinsViewCache& view, const uint256& txid)
{
    COutPoint iter(txid, 0);
    while (iter.n < MAX_OUTPUTS_PER_BLOCK) {
        const Coin& alternate = view.AccessCoin(iter);
        if (!alternate.IsSpent()) return alternate;
        ++iter.n;
    }
    return coinEmpty;
}