// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core developers
// Copyright (c) 2017-present The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <validationinterface.h>

#include <scheduler.h>
#include <txmempool.h>
#include <util/system.h>
#include <util/threadnames.h>
#include <validation.h>

#include <future>
#include <tuple>
#include <utility>

#include <boost/signals2/signal.hpp>

struct ValidationInterfaceConnections {
    boost::signals2::scoped_connection UpdatedBlockTip;
    boost::signals2::scoped_connection TransactionAddedToMempool;
    boost::signals2::scoped_connection TransactionDoubleSpent;
    boost::signals2::scoped_connection BadDSProofsDetectedFromNodeIds;
    boost::signals2::scoped_connection BlockConnected;
    boost::signals2::scoped_connection BlockDisconnected;
    boost::signals2::scoped_connection TransactionRemovedFromMempool;
    boost::signals2::scoped_connection ChainStateFlushed;
    boost::signals2::scoped_connection Broadcast;
    boost::signals2::scoped_connection BlockChecked;
    boost::signals2::scoped_connection NewPoWValidBlock;
};

struct MainSignalsInstance {
    boost::signals2::signal<void(const CBlockIndex *, const CBlockIndex *,
                                 bool fInitialDownload)>
        UpdatedBlockTip;
    boost::signals2::signal<void(const CTransactionRef &)>
        TransactionAddedToMempool;
    boost::signals2::signal<void(const CTransactionRef &, const DspId &)>
        TransactionDoubleSpent;
    boost::signals2::signal<void(const std::vector<NodeId> &)>
        BadDSProofsDetectedFromNodeIds;
    boost::signals2::signal<void(const std::shared_ptr<const CBlock> &,
                                 const CBlockIndex *pindex,
                                 const std::vector<CTransactionRef> &)>
        BlockConnected;
    boost::signals2::signal<void(const std::shared_ptr<const CBlock> &)>
        BlockDisconnected;
    boost::signals2::signal<void(const CTransactionRef &)>
        TransactionRemovedFromMempool;
    boost::signals2::signal<void(const CBlockLocator &)> ChainStateFlushed;
    boost::signals2::signal<void(int64_t nBestBlockTime, CConnman *connman)>
        Broadcast;
    boost::signals2::signal<void(const CBlock &, const CValidationState &)>
        BlockChecked;
    boost::signals2::signal<void(const CBlockIndex *,
                                 const std::shared_ptr<const CBlock> &)>
        NewPoWValidBlock;

    // We are not allowed to assume the scheduler only runs in one thread,
    // but must ensure all callbacks happen in-order, so we end up creating
    // our own queue here :(
    SingleThreadedSchedulerClient m_schedulerClient;
    std::unordered_map<CValidationInterface *, ValidationInterfaceConnections>
        m_connMainSignals;

    explicit MainSignalsInstance(CScheduler *pscheduler)
        : m_schedulerClient(pscheduler) {}
};

static CMainSignals g_signals;

// This map has to be a separate global instead of a member of
// MainSignalsInstance, because RegisterWithMempoolSignals is currently called
// before RegisterBackgroundSignalScheduler, so MainSignalsInstance hasn't been
// created yet.
static std::unordered_map<CTxMemPool *, boost::signals2::scoped_connection>
    g_connNotifyEntryRemoved;

void CMainSignals::RegisterBackgroundSignalScheduler(CScheduler &scheduler) {
    assert(!m_internals);
    m_internals.reset(new MainSignalsInstance(&scheduler));
}

void CMainSignals::UnregisterBackgroundSignalScheduler() {
    m_internals.reset(nullptr);
}

void CMainSignals::FlushBackgroundCallbacks() {
    if (m_internals) {
        m_internals->m_schedulerClient.EmptyQueue();
    }
}

size_t CMainSignals::CallbacksPending() {
    if (!m_internals) {
        return 0;
    }
    return m_internals->m_schedulerClient.CallbacksPending();
}

void CMainSignals::RegisterWithMempoolSignals(CTxMemPool &pool) {
    g_connNotifyEntryRemoved.emplace(
        std::piecewise_construct, std::forward_as_tuple(&pool),
        std::forward_as_tuple(pool.NotifyEntryRemoved.connect(
            std::bind(&CMainSignals::MempoolEntryRemoved, this,
                      std::placeholders::_1, std::placeholders::_2))));
}

void CMainSignals::UnregisterWithMempoolSignals(CTxMemPool &pool) {
    g_connNotifyEntryRemoved.erase(&pool);
}

CMainSignals &GetMainSignals() {
    return g_signals;
}

static bool IsImmediateModificationOfTheMainSignalsMapUnsafe(const SingleThreadedSchedulerClient &schedulerClient) {
    return schedulerClient.IsAcceptingJobs()
           && schedulerClient.GetServiceThread().get_id() != std::this_thread::get_id();
}

void RegisterValidationInterface(CValidationInterface *pwalletIn) {
    assert(g_signals.m_internals);
    std::promise<void> promise;
    auto func = [pwalletIn, &promise] {
        ValidationInterfaceConnections &conns = g_signals.m_internals->m_connMainSignals[pwalletIn];
        conns.UpdatedBlockTip = g_signals.m_internals->UpdatedBlockTip.connect(
            std::bind(&CValidationInterface::UpdatedBlockTip, pwalletIn, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3)
        );
        conns.TransactionAddedToMempool = g_signals.m_internals->TransactionAddedToMempool.connect(
            std::bind(&CValidationInterface::TransactionAddedToMempool, pwalletIn, std::placeholders::_1)
        );
        conns.BlockConnected = g_signals.m_internals->BlockConnected.connect(
            std::bind(&CValidationInterface::BlockConnected, pwalletIn, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3)
        );
        conns.BlockDisconnected = g_signals.m_internals->BlockDisconnected.connect(
            std::bind(&CValidationInterface::BlockDisconnected, pwalletIn, std::placeholders::_1)
        );
        conns.TransactionRemovedFromMempool = g_signals.m_internals->TransactionRemovedFromMempool.connect(
            std::bind(&CValidationInterface::TransactionRemovedFromMempool, pwalletIn, std::placeholders::_1)
        );
        conns.ChainStateFlushed = g_signals.m_internals->ChainStateFlushed.connect(
            std::bind(&CValidationInterface::ChainStateFlushed, pwalletIn, std::placeholders::_1)
        );
        conns.Broadcast = g_signals.m_internals->Broadcast.connect(
            std::bind(&CValidationInterface::ResendWalletTransactions, pwalletIn, std::placeholders::_1, std::placeholders::_2)
        );
        conns.BlockChecked = g_signals.m_internals->BlockChecked.connect(
            std::bind(&CValidationInterface::BlockChecked, pwalletIn, std::placeholders::_1, std::placeholders::_2)
        );
        conns.NewPoWValidBlock = g_signals.m_internals->NewPoWValidBlock.connect(
            std::bind(&CValidationInterface::NewPoWValidBlock, pwalletIn, std::placeholders::_1, std::placeholders::_2)
        );
        conns.TransactionDoubleSpent = g_signals.m_internals->TransactionDoubleSpent.connect(
            std::bind(&CValidationInterface::TransactionDoubleSpent, pwalletIn, std::placeholders::_1,
                      std::placeholders::_2)
        );
        conns.BadDSProofsDetectedFromNodeIds = g_signals.m_internals->BadDSProofsDetectedFromNodeIds.connect(
            std::bind(&CValidationInterface::BadDSProofsDetectedFromNodeIds, pwalletIn, std::placeholders::_1)
        );
        promise.set_value();
    };
    if (IsImmediateModificationOfTheMainSignalsMapUnsafe(g_signals.m_internals->m_schedulerClient)) {
        // This is necessary to ensure we don't touch m_connMainSignals from anything but the scheduler thread
        CallFunctionInValidationInterfaceQueue(std::move(func));
    } else {
        // Either we are *in* the scheduler thread *or* it's not running -- m_connMainSignals can be directly modified
        func();
    }
    promise.get_future().wait(); // so that we don't return until the above is completed.
}

void UnregisterValidationInterface(CValidationInterface *pwalletIn) {
    if (g_signals.m_internals) {
        std::promise<void> promise;
        auto func = [pwalletIn, &promise] {
            g_signals.m_internals->m_connMainSignals.erase(pwalletIn);
            promise.set_value();
        };
        if (IsImmediateModificationOfTheMainSignalsMapUnsafe(g_signals.m_internals->m_schedulerClient)) {
            // This is necessary to ensure we don't touch m_connMainSignals from anything but the scheduler thread
            CallFunctionInValidationInterfaceQueue(std::move(func));
        } else {
            // Either we are *in* the scheduler thread *or* it's not running -- m_connMainSignals can be directly modified
            func();
        }
        promise.get_future().wait(); // so that we don't return until the above is completed.
    }
}

void UnregisterAllValidationInterfaces() {
    if (!g_signals.m_internals) {
        return;
    }
    g_signals.m_internals->m_connMainSignals.clear();
}

void CallFunctionInValidationInterfaceQueue(std::function<void()> func) {
    g_signals.m_internals->m_schedulerClient.AddToProcessQueue(std::move(func));
}

void SyncWithValidationInterfaceQueue() {
    AssertLockNotHeld(cs_main);
    // Block until the validation queue drains
    std::promise<void> promise;
    CallFunctionInValidationInterfaceQueue([&promise] { promise.set_value(); });
    promise.get_future().wait();
}

void CMainSignals::MempoolEntryRemoved(CTransactionRef ptx,
                                       MemPoolRemovalReason reason) {
    if (reason != MemPoolRemovalReason::BLOCK &&
        reason != MemPoolRemovalReason::CONFLICT) {
        m_internals->m_schedulerClient.AddToProcessQueue(
            [ptx, this] { m_internals->TransactionRemovedFromMempool(ptx); });
    }
}

void CMainSignals::UpdatedBlockTip(const CBlockIndex *pindexNew,
                                   const CBlockIndex *pindexFork,
                                   bool fInitialDownload) {
    // Dependencies exist that require UpdatedBlockTip events to be delivered in
    // the order in which the chain actually updates. One way to ensure this is
    // for the caller to invoke this signal in the same critical section where
    // the chain is updated

    m_internals->m_schedulerClient.AddToProcessQueue([pindexNew, pindexFork,
                                                      fInitialDownload, this] {
        m_internals->UpdatedBlockTip(pindexNew, pindexFork, fInitialDownload);
    });
}

void CMainSignals::TransactionAddedToMempool(const CTransactionRef &ptx) {
    m_internals->m_schedulerClient.AddToProcessQueue(
        [ptx, this] { m_internals->TransactionAddedToMempool(ptx); });
}

void CMainSignals::TransactionDoubleSpent(const CTransactionRef &ptx, const DspId &dspId) {
    m_internals->m_schedulerClient.AddToProcessQueue(
        [ptx, dspId, this] { m_internals->TransactionDoubleSpent(ptx, dspId); });
}

void CMainSignals::BadDSProofsDetectedFromNodeIds(const std::vector<NodeId> &nodeIds) {
    m_internals->m_schedulerClient.AddToProcessQueue(
        [nodeIds, this] { m_internals->BadDSProofsDetectedFromNodeIds(nodeIds); });
}

void CMainSignals::BlockConnected(
    const std::shared_ptr<const CBlock> &pblock, const CBlockIndex *pindex,
    const std::shared_ptr<const std::vector<CTransactionRef>> &pvtxConflicted) {
    m_internals->m_schedulerClient.AddToProcessQueue(
        [pblock, pindex, pvtxConflicted, this] {
            m_internals->BlockConnected(pblock, pindex, *pvtxConflicted);
        });
}

void CMainSignals::BlockDisconnected(
    const std::shared_ptr<const CBlock> &pblock) {
    m_internals->m_schedulerClient.AddToProcessQueue(
        [pblock, this] { m_internals->BlockDisconnected(pblock); });
}

void CMainSignals::ChainStateFlushed(const CBlockLocator &locator) {
    m_internals->m_schedulerClient.AddToProcessQueue(
        [locator, this] { m_internals->ChainStateFlushed(locator); });
}

void CMainSignals::Broadcast(int64_t nBestBlockTime, CConnman *connman) {
    m_internals->Broadcast(nBestBlockTime, connman);
}

void CMainSignals::BlockChecked(const CBlock &block,
                                const CValidationState &state) {
    m_internals->BlockChecked(block, state);
}

void CMainSignals::NewPoWValidBlock(
    const CBlockIndex *pindex, const std::shared_ptr<const CBlock> &block) {
    m_internals->NewPoWValidBlock(pindex, block);
}
