#include "BlockProc.h"
#include "BTC.h"
#include "Controller.h"
#include "TXO.h"

#include "robin_hood/robin_hood.h"

#include <algorithm>
#include <cassert>
#include <iterator>
#include <list>
#include <map>

Controller::Controller(const std::shared_ptr<Options> &o)
    : Mgr(nullptr), options(o)
{
    setObjectName("Controller");
    _thread.setObjectName(objectName());
}

Controller::~Controller() { Debug("%s", __FUNCTION__); cleanup(); }

void Controller::startup()
{
    stopFlag = false;

    storage = std::make_unique<Storage>(options);
    storage->startup(); // may throw here

    bitcoindmgr = std::make_unique<BitcoinDMgr>(options->bitcoind.first, options->bitcoind.second, options->rpcuser, options->rpcpassword);
    {
        auto constexpr waitTimer = "wait4bitcoind", callProcessTimer = "callProcess";
        int constexpr msgPeriod = 10000, // 10sec
                      smallDelay = 100;

        // some setup code that waits for bitcoind to be ready before kicking off our "process" method
        auto waitForBitcoinD = [this] {
            lostConn = true;
            stopTimer(pollTimerName);
            stopTimer(callProcessTimer);
            callOnTimerSoon(msgPeriod, waitTimer, []{ Log("Waiting for bitcoind..."); return true; }, false, Qt::TimerType::VeryCoarseTimer);
        };
        waitForBitcoinD();
        conns += connect(bitcoindmgr.get(), &BitcoinDMgr::allConnectionsLost, this, waitForBitcoinD);
        conns += connect(bitcoindmgr.get(), &BitcoinDMgr::gotFirstGoodConnection, this, [this](quint64 id) {
            // connection to kick off our 'process' method once the first auth is received
            if (lostConn) {
                lostConn = false;
                stopTimer(waitTimer);
                Debug() << "Auth recvd from bicoind with id: " << id << ", proceeding with processing ...";
                callOnTimerSoonNoRepeat(smallDelay, callProcessTimer, [this]{process();}, true);
            }
        });
        conns += connect(bitcoindmgr.get(), &BitcoinDMgr::inWarmUp, this, [last = -1.0](const QString &msg) mutable {
            // just print a message to the log as to why we keep dropping conn. -- if bitcoind is still warming up
            auto now = Util::getTimeSecs();
            if (now-last >= 1.0) { // throttled to not spam log
                last = now;
                Log() << "bitcoind is still warming up: " << msg;
            }
        });
    }

    bitcoindmgr->startup(); // may throw

    // We defer listening for connections until we hit the "upToDate" state at least once, to prevent problems
    // for clients.
    auto connPtr = std::make_shared<QMetaObject::Connection>();
    *connPtr = connect(this, &Controller::upToDate, this, [this, connPtr] {
        if (connPtr) disconnect(*connPtr);
        if (!srvmgr) {
            if (!origThread) {
                Fatal() << "INTERNAL ERROR: Controller's creation thread is null; cannot start SrvMgr, exiting!";
                return;
            }
            srvmgr = std::make_unique<SrvMgr>(options->interfaces);
            // this object will live on our creation thread (normally the main thread)
            srvmgr->moveToThread(origThread);
            // now, start it up on our creation thread (normally the main thread)
            Util::VoidFuncOnObjectNoThrow(srvmgr.get(), [this]{
                // creation thread (normally the main thread)
                try {
                    srvmgr->startup(); // may throw Exception, waits for servers to bind
                } catch (const Exception & e) {
                    // exit app on bind/listen failure.
                    Fatal() << e.what();
                }
            }); // wait for srvmgr's thread (usually the main thread)
        }
    }, Qt::QueuedConnection);

    start();  // start our thread
}

void Controller::cleanup()
{
    stopFlag = true;
    stop();
    tasks.clear(); // deletes all tasks asap
    if (srvmgr) { Log("Stopping SrvMgr ... "); srvmgr->cleanup(); srvmgr.reset(); }
    if (bitcoindmgr) { Log("Stopping BitcoinDMgr ... "); bitcoindmgr->cleanup(); bitcoindmgr.reset(); }
    if (storage) { Log("Closing storage ..."); storage->cleanup(); storage.reset(); }
    sm.reset();
}

/// Encapsulates basically the data returned from bitcoind by the getblockchaininfo RPC method.
/// This has been separated out into its own struct for future use to detect blockchain changes.
/// TODO: Refactor this out to storage, etc to detect when blockchain changed.
struct ChainInfo {
    QString toString() const;

    QString chain = "";
    int blocks = 0, headers = -1;
    QByteArray bestBlockhash; ///< decoded bytes
    double difficulty = 0.0;
    int64_t mtp = 0;
    double verificationProgress = 0.0;
    bool initialBlockDownload = false;
    QByteArray chainWork; ///< decoded bytes
    size_t sizeOnDisk = 0;
    bool pruned = false;
    QString warnings;
};

struct GetChainInfoTask : public CtlTask
{
    GetChainInfoTask(Controller *ctl_) : CtlTask(ctl_, "Task.GetChainInfo") {}
    ~GetChainInfoTask() override { stop(); } // paranoia
    void process() override;

    ChainInfo info;
};

void GetChainInfoTask::process()
{
    submitRequest("getblockchaininfo", {}, [this](const RPC::Message & resp){
        const auto Err = [this, id=resp.id.toInt()](const QString &thing) {
            const auto msg = QString("Failed to parse %1").arg(thing);
            errorCode = id;
            errorMessage = msg;
            throw Exception(msg);
        };
        try {
            bool ok = false;
            const auto map = resp.result().toMap();

            if (map.isEmpty()) Err("response; expected map");

            info.blocks = map.value("blocks").toInt(&ok);
            if (!ok || info.blocks < 0) Err("blocks"); // enforce positive blocks number

            info.chain = map.value("chain").toString();
            if (info.chain.isEmpty()) Err("chain");

            info.headers = map.value("headers").toInt(); // error ignored here

            info.bestBlockhash = Util::ParseHexFast(map.value("bestblockhash").toByteArray());
            if (info.bestBlockhash.size() != HashLen) Err("bestblockhash");

            info.difficulty = map.value("difficulty").toDouble(); // error ignored here
            info.mtp = map.value("mediantime").toLongLong(); // error ok
            info.verificationProgress = map.value("verificationprogress").toDouble(); // error ok

            if (auto v = map.value("initialblockdownload"); v.canConvert<bool>())
                info.initialBlockDownload = v.toBool();
            else
                Err("initialblockdownload");

            info.chainWork = Util::ParseHexFast(map.value("chainwork").toByteArray()); // error ok
            info.sizeOnDisk = map.value("size_on_disk").toULongLong(); // error ok
            info.pruned = map.value("pruned").toBool(); // error ok
            info.warnings = map.value("warnings").toString(); // error ok

            if (Trace::isEnabled()) Trace() << info.toString();

            emit success();
        } catch (const Exception & e) {
            Error() << "INTERNAL ERROR: " << e.what();
            emit errored();
        }
    });
}

QString ChainInfo::toString() const
{
    QString ret;
    {
        QTextStream ts(&ret, QIODevice::WriteOnly|QIODevice::Truncate);
        ts << "(ChainInfo"
           << " chain: \"" << chain << "\""
           << " blocks: " << blocks
           << " headers: " << headers
           << " bestBlockHash: " << bestBlockhash.toHex()
           << " difficulty: " << QString::number(difficulty, 'f', 9)
           << " mtp: " << mtp
           << " verificationProgress: " << QString::number(verificationProgress, 'f', 6)
           << " ibd: " << initialBlockDownload
           << " chainWork: " << chainWork.toHex()
           << " sizeOnDisk: " << sizeOnDisk
           << " pruned: " << pruned
           << " warnings: \"" << warnings << "\""
           << ")";
    }
    return ret;
}

struct DownloadBlocksTask : public CtlTask
{
    DownloadBlocksTask(unsigned from, unsigned to, unsigned stride, Controller *ctl);
    ~DownloadBlocksTask() override { stop(); } // paranoia
    void process() override;


    const unsigned from = 0, to = 0, stride = 1, expectedCt = 1;
    unsigned next = 0;
    std::atomic_uint goodCt = 0;
    bool maybeDone = false;

    int q_ct = 0;
    static constexpr int max_q = /*16;*/BitcoinDMgr::N_CLIENTS+1; // todo: tune this

    static const int HEADER_SIZE;

    std::atomic<size_t> nTx = 0, nIns = 0, nOuts = 0;

    void do_get(unsigned height);

    // basically computes expectedCt. Use expectedCt member to get the actual expected ct. this is used only by c'tor as a utility function
    static size_t nToDL(unsigned from, unsigned to, unsigned stride)  { return size_t( (((to-from)+1) + stride-1) / qMax(stride, 1U) ); }
    // thread safe, this is a rough estimate and not 100% accurate
    size_t nSoFar(double prog=-1) const { if (prog<0.) prog = lastProgress; return size_t(qRound(expectedCt * prog)); }
    // given a position in the headers array, return the height
    size_t index2Height(size_t index) { return size_t( from + (index * stride) ); }
    // given a block height, return the index into our array
    size_t height2Index(size_t h) { return size_t( ((h-from) + stride-1) / stride ); }
};


/*static*/ const int DownloadBlocksTask::HEADER_SIZE = BTC::GetBlockHeaderSize();

DownloadBlocksTask::DownloadBlocksTask(unsigned from, unsigned to, unsigned stride, Controller *ctl_)
    : CtlTask(ctl_, QString("Task.DL %1 -> %2").arg(from).arg(to)), from(from), to(to), stride(stride), expectedCt(unsigned(nToDL(from, to, stride)))
{
    FatalAssert( (to >= from) && (ctl_) && (stride > 0)) << "Invalid params to DonloadBlocksTask c'tor, FIXME!";

    next = from;
}

void DownloadBlocksTask::process()
{
    if (next > to) {
        if (maybeDone) {
            if (goodCt >= expectedCt)
                emit success();
            else {
                errorCode = int(expectedCt - goodCt);
                errorMessage = QString("missing %1 blocks").arg(errorCode);
                emit errored();
            }
        }
        return;
    }

    do_get(next);
    next += stride;
}

void DownloadBlocksTask::do_get(unsigned int bnum)
{
    if (ctl->isStopping())  return; // short-circuit early return if controller is stopping
    if (unsigned msec = ctl->downloadTaskRecommendedThrottleTimeMsec(bnum); msec > 0) {
        // Controller told us to back off because it is backlogged.
        // Schedule ourselves to run again soon and return.
        Util::AsyncOnObject(this, [this, bnum]{
            do_get(bnum);
        }, msec, Qt::TimerType::PreciseTimer);
        return;
    }
    submitRequest("getblockhash", {bnum}, [this, bnum](const RPC::Message & resp){
        QVariant var = resp.result();
        const auto hash = Util::ParseHexFast(var.toByteArray());
        if (hash.length() == HashLen) {
            submitRequest("getblock", {var, false}, [this, bnum, hash](const RPC::Message & resp){
                QVariant var = resp.result();
                const auto rawblock = Util::ParseHexFast(var.toByteArray());
                const auto header = rawblock.left(HEADER_SIZE); // we need a deep copy of this anyway so might as well take it now.
                QByteArray chkHash;
                if (bool sizeOk = header.length() == HEADER_SIZE; sizeOk && (chkHash = BTC::HashRev(header)) == hash) {
                    auto ppb = PreProcessedBlock::makeShared(bnum, size_t(rawblock.size()), BTC::Deserialize<bitcoin::CBlock>(rawblock)); // this is here to test performance
                    // TESTING --
                    //if (bnum == 60000) Debug() << ppb->toDebugString();

                    if (Trace::isEnabled()) Trace() << "block " << bnum << " size: " << rawblock.size() << " nTx: " << ppb->txInfos.size();
                    // update some stats for /stats endpoint
                    nTx += ppb->txInfos.size();
                    nOuts += ppb->outputs.size();
                    nIns += ppb->inputs.size();

                    const size_t index = height2Index(bnum);
                    ++goodCt;
                    q_ct = qMax(q_ct-1, 0);
                    lastProgress = double(index) / double(expectedCt);
                    if (!(bnum % 1000) && bnum) {
                        emit progress(lastProgress);
                    }
                    if (Trace::isEnabled()) Trace() << resp.method << ": header for height: " << bnum << " len: " << header.length();
                    ctl->putBlock(this, ppb); // send the block off to the Controller thread for further processing and for save to db
                    if (goodCt >= expectedCt) {
                        // flag state to maybeDone to do checks when process() called again
                        maybeDone = true;
                        AGAIN();
                        return;
                    }
                    while (goodCt + unsigned(q_ct) < expectedCt && q_ct < max_q) {
                        // queue multiple at once
                        AGAIN();
                        ++q_ct;
                    }
                } else if (!sizeOk) {
                    Warning() << resp.method << ": at height " << bnum << " header not valid (decoded size: " << header.length() << ")";
                    errorCode = int(bnum);
                    errorMessage = QString("bad size for height %1").arg(bnum);
                    emit errored();
                } else {
                    Warning() << resp.method << ": at height " << bnum << " header not valid (expected hash: " << hash.toHex() << ", got hash: " << chkHash.toHex() << ")";
                    errorCode = int(bnum);
                    errorMessage = QString("hash mismatch for height %1").arg(bnum);
                    emit errored();
                }
            });
        } else {
            Warning() << resp.method << ": at height " << bnum << " hash not valid (decoded size: " << hash.length() << ")";
            errorCode = int(bnum);
            errorMessage = QString("invalid hash for height %1").arg(bnum);
            emit errored();
        }
    });
}

struct Controller::StateMachine
{
    enum State {
        Begin=0, GetBlocks, DownloadingBlocks, FinishedDL, End, Failure, IBD, Retry,
    };
    State state = Begin;
    int ht = -1; ///< the latest height bitcoind told us this run
    bool isMainNet = false;

    robin_hood::unordered_flat_map<unsigned, PreProcessedBlockPtr> ppBlocks; // mapping of height -> PreProcessedBlock (we use an unordered_flat_map because it's faster for frequent updates)
    unsigned startheight = 0, ///< the height we started at
             endHeight = 0; ///< the final (inclusive) block height we expect to receive to pronounce the synch done

    std::atomic<unsigned> ppBlkHtNext = 0;  ///< the next unprocessed block height we need to process in series

    // todo: tune this
    const size_t DL_CONCURRENCY = qMax(Util::getNPhysicalProcessors()-1, 1U);//size_t(qMin(qMax(int(Util::getNPhysicalProcessors())-BitcoinDMgr::N_CLIENTS, BitcoinDMgr::N_CLIENTS), 32));

    size_t nTx = 0, nIns = 0, nOuts = 0;

    const char * stateStr() const {
        static constexpr const char *stateStrings[] = { "Begin", "GetBlocks", "DownloadingBlocks", "FinishedDL", "End",
                                                        "Failure", "IBD", "Retry",
                                                        "Unknown" /* this should always be last */ };
        auto idx = qMin(size_t(state), std::size(stateStrings)-1);
        return stateStrings[idx];
    }

    static constexpr unsigned progressIntervalBlocks = 1000;
    size_t nProgBlocks = 0, nProgIOs = 0, nProgTx = 0;
    double lastProgTs = 0.;
};

unsigned Controller::downloadTaskRecommendedThrottleTimeMsec(unsigned bnum) const
{
    std::shared_lock g(smLock); // this lock guarantees that 'sm' won't be deleted from underneath us
    if (sm) {
        int maxBackLog = 1000; // <--- TODO: have this be a more dynamic value based on current average blocksize.
        if (sm->isMainNet) {
            // mainnet
            if (bnum > 150000) // beyond this height the blocks are starting to be big enough that we want to not eat memory.
                maxBackLog = 250;
            else if (bnum > 550000) // beyond this height we may start to see 32MB blocks in the future
                maxBackLog = 100;
        } else {
            // testnet
            if (bnum > 1300000) // beyond this height 32MB blocks may be common, esp. in the future
                maxBackLog = 100;
        }

        const int diff = int(bnum) - int(sm->ppBlkHtNext.load()); // note: ppBlkHtNext is not guarded by the lock but it is an atomic value, so that's fine.
        if ( diff > maxBackLog ) {
            // Make the backoff time be from 10ms to 50ms, depending on how far in the future this block height is from
            // what we are processing.  The hope is that this enforces some order on future block arrivals and also
            // prevents excessive polling for blocks that are too far ahead of us.
            return std::min(10u + 5*unsigned(diff - maxBackLog - 1), 50u); // TODO: also have this be tuneable.
        }

    }
    return 0u;
}

void Controller::rmTask(CtlTask *t)
{
    if (auto it = tasks.find(t); it != tasks.end()) {
        tasks.erase(it); // will delete object immediately
        return;
    }
    Error() << __FUNCTION__ << ": Task '" << t->objectName() << "' not found! FIXME!";
}

bool Controller::isTaskDeleted(CtlTask *t) const { return tasks.count(t) == 0; }

void Controller::add_DLHeaderTask(unsigned int from, unsigned int to, size_t nTasks)
{
    DownloadBlocksTask *t = newTask<DownloadBlocksTask>(false, unsigned(from), unsigned(to), unsigned(nTasks), this);
    connect(t, &CtlTask::success, this, [t, this]{
        if (UNLIKELY(!sm || isTaskDeleted(t))) return; // task was stopped from underneath us, this is stale.. abort.
        sm->nTx += t->nTx;
        sm->nIns += t->nIns;
        sm->nOuts += t->nOuts;
        Debug() << "Got all blocks from: " << t->objectName() << " blockCt: "  << t->goodCt
                << " nTx,nInp,nOutp: " << t->nTx << "," << t->nIns << "," << t->nOuts << " totals: "
                << sm->nTx << "," << sm->nIns << "," << sm->nOuts;
    });
    connect(t, &CtlTask::errored, this, [t, this]{
        if (UNLIKELY(!sm || isTaskDeleted(t))) return; // task was stopped from underneath us, this is stale.. abort.
        if (sm->state == StateMachine::State::Failure) return; // silently ignore if we are already in failure
        Error() << "Task errored: " << t->objectName() << ", error: " << t->errorMessage;
        genericTaskErrored();
    });
}

void Controller::genericTaskErrored()
{
    if (sm && sm->state != StateMachine::State::Failure) {
        sm->state = StateMachine::State::Failure;
        AGAIN();
    }
}

template <typename CtlTaskT, typename ...Args, typename /* enable_if... */>
CtlTaskT *Controller::newTask(bool connectErroredSignal, Args && ...args)
{
    CtlTaskT *task = new CtlTaskT(std::forward<Args>(args)...);
    tasks.emplace(task, task);
    if (connectErroredSignal)
        connect(task, &CtlTask::errored, this, &Controller::genericTaskErrored);
    QTimer::singleShot(0, this, [task, this] {
        if (!isTaskDeleted(task))
            task->start();
    });
    return task;
}

void Controller::process(bool beSilentIfUpToDate)
{
    if (stopFlag) return;
    bool enablePollTimer = false;
    auto polltimeout = polltime_ms;
    stopTimer(pollTimerName);
    //Debug() << "Process called...";
    if (!sm) {
        std::lock_guard g(smLock);
        sm = std::make_unique<StateMachine>();
    }
    using State = StateMachine::State;
    if (sm->state == State::Begin) {
        auto task = newTask<GetChainInfoTask>(true, this);
        connect(task, &CtlTask::success, this, [this, task, beSilentIfUpToDate]{
            if (UNLIKELY(!sm || isTaskDeleted(task))) return; // task was stopped from underneath us, this is stale.. abort.
            if (task->info.initialBlockDownload) {
                sm->state = State::IBD;
                AGAIN();
                return;
            }
            if (const auto dbchain = storage->getChain(); dbchain.isEmpty() && !task->info.chain.isEmpty()) {
                storage->setChain(task->info.chain);
            } else if (dbchain != task->info.chain) {
                Fatal() << "Bitcoind reports chain: \"" << task->info.chain << "\", which differs from our database: \""
                        << dbchain << "\". You may have connected to the wrong bitcoind. To fix this issue either "
                        << "connect to a different bitcoind or delete this program's datadir to resynch.";
                return;
            }
            sm->isMainNet = task->info.chain == "main";
            // TODO: detect reorgs here -- to be implemented later after we figure out data model more, etc.
            const auto [old, oldHash] = storage->latestTip();
            sm->ht = task->info.blocks;
            if (old == sm->ht) {
                if (task->info.bestBlockhash == oldHash) { // no reorg
                    if (!beSilentIfUpToDate) {
                        Log() << "Block height " << sm->ht << ", up-to-date";
                        emit upToDate();
                    }
                    sm->state = State::End;
                } else {
                    // height ok, but best block hash mismatch.. reorg
                    Warning() << "We have bestBlock " << oldHash.toHex() << ", but bitcoind reports bestBlock " << task->info.bestBlockhash.toHex() << "."
                              << " Possible reorg, will rewind back 1 block and try again ...";
                    process_DoUndoAndRetry(); // attempt to undo 1 block and try again.
                    return;
                }
            } else if (old > sm->ht) {
                Warning() << "We have height " << old << ", but bitcoind reports height " << sm->ht << "."
                          << " Possible reorg, will rewind back 1 block and try again ...";
                process_DoUndoAndRetry(); // attempt to undo 1 block and try again.
                return;
            } else {
                Log() << "Block height " << sm->ht << ", downloading new blocks ...";
                emit synchronizing();
                sm->state = State::GetBlocks;
            }
            AGAIN();
        });
    } else if (sm->state == State::GetBlocks) {
        FatalAssert(sm->ht >= 0) << "Inconsistent state -- sm->ht cannot be negative in State::GetBlocks! FIXME!"; // paranoia
        const size_t base = size_t(storage->latestTip().first+1);
        const size_t num = size_t(sm->ht+1) - base;
        FatalAssert(num > 0) << "Cannot download 0 blocks! FIXME!"; // more paranoia
        const size_t nTasks = qMin(num, sm->DL_CONCURRENCY);
        sm->lastProgTs = Util::getTimeSecs();
        sm->ppBlkHtNext = sm->startheight = unsigned(base);
        sm->endHeight = unsigned(sm->ht);
        for (size_t i = 0; i < nTasks; ++i) {
            add_DLHeaderTask(unsigned(base + i), unsigned(sm->ht), nTasks);
        }
        sm->state = State::DownloadingBlocks; // advance state now. we will be called back by download task in putBlock()
    } else if (sm->state == State::DownloadingBlocks) {
        process_DownloadingBlocks();
    } else if (sm->state == State::FinishedDL) {
        size_t N = sm->endHeight - sm->startheight + 1;
        Log() << "Processed " << N << " new " << Util::Pluralize("block", N) << " with " << sm->nTx << " " << Util::Pluralize("tx", sm->nTx)
              << " (" << sm->nIns << " " << Util::Pluralize("input", sm->nIns) << " & " << sm->nOuts << " " << Util::Pluralize("output", sm->nOuts) << ")"
              << ", verified ok.";
        {
            std::lock_guard g(smLock);
            sm.reset(); // go back to "Begin" state to check if any new headers arrived in the meantime
        }
        AGAIN();
    } else if (sm->state == State::Retry) {
        // normally the result of Rewinding due to reorg, retry right away.
        Debug() << "Retrying download again ...";
        {
            std::lock_guard g(smLock);
            sm.reset();
        }
        AGAIN();
    } else if (sm->state == State::Failure) {
        // We will try again later via the pollTimer
        Error() << "Failed to download blocks";
        {
            std::lock_guard g(smLock);
            sm.reset();
        }
        enablePollTimer = true;
        emit synchFailure();
    } else if (sm->state == State::End) {
        {
            std::lock_guard g(smLock);
            sm.reset();  // great success!
        }
        enablePollTimer = true;
    } else if (sm->state == State::IBD) {
        {
            std::lock_guard g(smLock);
            sm.reset();  // great success!
        }
        enablePollTimer = true;
        Warning() << "bitcoind is in initial block download, will try again in 1 minute";
        polltimeout = 60 * 1000; // try again every minute
        emit synchFailure();
    }

    if (enablePollTimer)
        callOnTimerSoonNoRepeat(polltimeout, pollTimerName, [this]{if (!sm) process(true);});
}

void Controller::putBlock(CtlTask *task, PreProcessedBlockPtr p)
{
    // returns right away
    Util::AsyncOnObject(this, [this, task, p] {
        if (!sm || isTaskDeleted(task) || sm->state == StateMachine::State::Failure || stopFlag) {
            Debug() << "Ignoring block " << p->height << " for now-defunct task";
            return;
        } else if (sm->state != StateMachine::State::DownloadingBlocks) {
            Debug() << "Ignoring putBlocks request for block " << p->height << " -- state is not \"DownloadingBlocks\" but rather is: \"" << sm->stateStr() << "\"";
            return;
        }
        sm->ppBlocks[p->height] = p;
        //AGAIN(); // queue up, return right away -- turns out this spams events. better to call the process function directly here.
        process_DownloadingBlocks();
    });
}

void Controller::process_PrintProgress(unsigned height, size_t nTx, size_t nIO)
{
    if (UNLIKELY(!sm)) return; // paranaoia
    sm->nProgBlocks++;
    sm->nProgTx += nTx;
    sm->nProgIOs += nIO;
    if (UNLIKELY(height && !(height % sm->progressIntervalBlocks))) {
        static const auto formatRate = [](double rate, const QString & thing, bool addComma = true) {
            QString unit = "sec";
            if (rate < 1.0 && rate > 0.0) {
                rate *= 60.0;
                unit = "min";
            }
            if (rate < 1.0 && rate > 0.0) {
                rate *= 60.0;
                unit = "hour";
            }
            static const auto format = [](double rate) { return QString::number(rate, 'f', rate < 10. ? (rate < 1.0 ? 3 : 2) : 1); };
            return rate > 0.0 ? QString("%1%2 %3/%4").arg(addComma ? ", " : "").arg(format(rate)).arg(thing).arg(unit) : QString();
        };
        const double now = Util::getTimeSecs();
        const double elapsed = std::max(now - sm->lastProgTs, 0.00001); // ensure no division by zero
        QString pctDisplay = QString::number((height*1e2) / std::max(sm->endHeight, 1U), 'f', 1) + "%";
        const double rateBlocks = sm->nProgBlocks / elapsed;
        const double rateIO = sm->nProgIOs / elapsed;
        Log() << "Processed height: " << height << ", " << pctDisplay << formatRate(rateBlocks, "blocks") << formatRate(rateIO, "ins & outs");
        // update/reset ts and counters
        sm->lastProgTs = now;
        sm->nProgBlocks = sm->nProgTx = sm->nProgIOs = 0;
    }
}

void Controller::process_DownloadingBlocks()
{
    unsigned ct = 0;

    for (auto it = sm->ppBlocks.find(sm->ppBlkHtNext); it != sm->ppBlocks.end() && !stopFlag; it = sm->ppBlocks.find(sm->ppBlkHtNext)) {
        auto ppb = it->second;
        assert(ppb->height == sm->ppBlkHtNext); // paranoia -- should never happen
        ++ct;

        ++sm->ppBlkHtNext;
        sm->ppBlocks.erase(it); // remove immediately from q

        // process & add it if it's good
        if ( ! process_VerifyAndAddBlock(ppb) )
            // error encountered.. abort!
            return;

        process_PrintProgress(ppb->height, ppb->txInfos.size(), ppb->inputs.size()+ppb->outputs.size());

        if (sm->ppBlkHtNext > sm->endHeight) {
            sm->state = StateMachine::State::FinishedDL;
            AGAIN();
            return;
        }

    }

    // testing debug
    //if (auto backlog = sm->ppBlocks.size(); backlog < 100 || ct > 100) {
    //    Debug() << "ppblk - processed: " << ct << ", backlog: " << backlog;
    //}
}

bool Controller::process_VerifyAndAddBlock(PreProcessedBlockPtr ppb)
{
    assert(sm);

    try {
        const auto nLeft = qMax(sm->endHeight - (sm->ppBlkHtNext-1), 0U);
        const bool saveUndoInfo = int(ppb->height) > (sm->ht - int(BTC::maxReorgDepth));

        storage->addBlock(ppb, saveUndoInfo, nLeft);

    } catch (const HeaderVerificationFailure & e) {
        Debug() << "addBlock exception: " << e.what();
        Log() << "Possible reorg detected at height " << ppb->height << ", rewinding 1 block and trying again ...";
        process_DoUndoAndRetry();
        return false;
    } catch (const std::exception & e) {
        Fatal() << e.what(); // TODO: see about more graceful error and not a fatal exit. (although if we do get an error here it's pretty non-recoverable!)
        sm->state = StateMachine::State::Failure;
        AGAIN(); // schedule us again to do cleanup
        return false;
    }

    return true;
}

void Controller::process_DoUndoAndRetry()
{
    assert(sm);
    try {
        storage->undoLatestBlock();
        // . <-- If we get here, rollback was successful.
        // We flag the state to retry, which retries the full download right away
        // (Note: this may trigger us to roll back again and again until we reorg to the sufficient depth).
        sm->state = StateMachine::State::Retry;
        AGAIN(); // schedule us again to do cleanup
    } catch (const std::exception & e) {
        Fatal() << "Failed to rewind: " << e.what() << "\n\nThe database is now likely in an inconsistent state."
                << " You will need to delete the datadir and do a full resynch now. Sorry!\n";
        sm->state = StateMachine::State::Failure;
        return; // return immediately from event loop -- app will shut down now. :/
    }
}

// -- CtlTask
CtlTask::CtlTask(Controller *ctl, const QString &name)
    : QObject(nullptr), ctl(ctl)
{
    setObjectName(name);
    _thread.setObjectName(name);
}

CtlTask::~CtlTask() {
    Debug("%s (%s)", __FUNCTION__, objectName().isEmpty() ? "" : objectName().toUtf8().constData());
    stop();
}

void CtlTask::on_started()
{
    ThreadObjectMixin::on_started();
    conns += connect(this, &CtlTask::success, ctl, [this]{stop();});
    conns += connect(this, &CtlTask::errored, ctl, [this]{stop();});
    conns += connect(this, &CtlTask::finished, ctl, [this]{ctl->rmTask(this);});
    process();
    emit started();
}

void CtlTask::on_finished()
{
    ThreadObjectMixin::on_finished();
    emit finished();
}

void CtlTask::on_error(const RPC::Message &resp)
{
    Warning() << resp.method << ": error response: " << resp.toJsonString();
    errorCode = resp.errorCode();
    errorMessage = resp.errorMessage();
    emit errored();
}
void CtlTask::on_failure(const RPC::Message::Id &id, const QString &msg)
{
    Warning() << id.toString() << ": FAIL: " << msg;
    errorCode = id.toInt();
    errorMessage = msg;
    emit errored();
}
quint64 CtlTask::submitRequest(const QString &method, const QVariantList &params, const BitcoinDMgr::ResultsF &resultsFunc)
{
    quint64 id = IdMixin::newId();
    ctl->bitcoindmgr->submitRequest(this, id, method, params,
                                    resultsFunc,
                                    [this](const RPC::Message &r){on_error(r);},
                                    [this](const RPC::Message::Id &id, const QString &msg){on_failure(id, msg);});
    return id;
}



// --- Controller stats
auto Controller::stats() const -> Stats
{
    // "Servers"
    auto st = QVariantMap{{ "Servers", srvmgr ? srvmgr->statsSafe() : QVariant() }};

    // "BitcoinD's"
    st["Bitcoin Daemon"] = bitcoindmgr->statsSafe();

    // "Controller" (self)
    QVariantMap m;
    const auto tipInfo = storage->latestTip();
    m["Header count"] = tipInfo.first+1;
    m["Chain"] = storage->getChain();
    m["Chain tip"] = tipInfo.second.toHex();
    m["UTXO set"] = qlonglong(storage->utxoSetSize());
    m["UTXO set bytes"] = QString::number(storage->utxoSetSizeMiB(), 'f', 3) + " MiB";
    const auto txnum = qlonglong(storage->getTxNum());
    m["TxNum"] = txnum;
    m["TxNum -> TxHash (latest)"] = txnum ? storage->hashForTxNum(TxNum(txnum-1), false, nullptr, true).value_or("").toHex() : QVariant();
    if (sm) {
        QVariantMap m2;
        m2["State"] = sm->stateStr();
        m2["Height"] = sm->ht;
        if (const auto nDL = nBlocksDownloadedSoFar(); nDL > 0)
            m2["Blocks downloaded this run"] = qlonglong(nDL);
        if (const auto [ntx, nin, nout] = nTxInOutSoFar(); ntx > 0) {
            m2["Txs seen this run"] = QVariantMap({
                { "nTx" , qlonglong(ntx) },
                { "nIns", qlonglong(nin) },
                { "nOut", qlonglong(nout) }
            });
        }
        const size_t backlogBlocks = sm->ppBlocks.size();
        if (backlogBlocks) {
            QVariantMap m3;
            m3["numBlocks"] = qulonglong(backlogBlocks);
            size_t backlogBytes = 0, backlogTxs = 0, backlogInMemoryBytes = 0;
            for (const auto & [height, ppb] : sm->ppBlocks) {
                backlogBytes += ppb->sizeBytes;
                backlogTxs += ppb->txInfos.size();
                backlogInMemoryBytes += ppb->estimatedThisSizeBytes;
            }
            m3["in-memory (est.)"] = QString("%1 MiB").arg(QString::number(double(backlogInMemoryBytes) / 1e6, 'f', 3));
            m3["block bytes"] = QString("%1 MiB").arg(QString::number(double(backlogBytes) / 1e6, 'f', 3));
            m3["numTxs"] = qulonglong(backlogTxs);
            m2["BackLog"] = m3;
        } else {
            m2["BackLog"] = QVariant(); // null
        }
        m["StateMachine"] = m2;
    } else
        m["StateMachine"] = QVariant(); // null
    QVariantMap timerMap;
    for (const auto & timer: _timerMap) {
        timerMap.insert(timer->objectName(), timer->interval());
    }
    m["activeTimers"] = timerMap;
    QVariantList l;
    { // task list
        const auto now = Util::getTime();
        for (const auto & [task, ign] : tasks) {
            Q_UNUSED(ign)
            l.push_back(QVariantMap{{ task->objectName(), QVariantMap{
                {"age", QString("%1 sec").arg(double((now-task->ts)/1e3))} ,
                {"progress" , QString("%1%").arg(QString::number(task->lastProgress*100.0, 'f', 1)) }}
            }});
        }
        Util::updateMap(m, QVariantMap{{"tasks" , l}});
    }
    st["Controller"] = m;
    st["Storage"] = storage->statsSafe();
    return st;
}

auto Controller::debug(const StatsParams &p) const -> Stats // from StatsMixin
{
    QVariantMap ret;
    bool ok;
    const auto t0 = Util::getTimeNS();
    if (const auto txnum = p.value("txnum").toULong(&ok); ok) {
        QVariantMap m;
        auto hash = storage->hashForTxNum(txnum).value_or(QByteArray());
        auto opt = storage->heightForTxNum(txnum);
        m["tx_hash"] = Util::ToHexFast(hash);
        m["height"] = opt.has_value() ? int(opt.value()) : -1;
        ret["txnum_debug"] = m;
    }
    if (const auto sh = QByteArray::fromHex(p.value("sh").toLatin1()); sh.length() == HashLen) {
        QVariantList l;

        auto items = storage->getHistory(sh);
        for (const auto & item : items) {
            QVariantMap m;
            m["tx_hash"] = Util::ToHexFast(item.hash);
            m["height"] = item.height;
            l.push_back(m);
        }
        ret["sh_debug"] = l;
    }
    if (const auto hashx = QByteArray::fromHex(p.value("unspent").toLatin1()); hashx.length() == HashLen) {
        QVariantList l;

        auto items = storage->listUnspent(hashx);
        for (const auto & item : items) {
            QVariantMap m;
            m["tx_hash"] = Util::ToHexFast(item.hash);
            m["height"] = item.height;
            m["tx_pos"] = item.tx_pos;
            m["value"] = item.value / item.value.satoshi();
            l.push_back(m);
        }
        ret["unspent_debug"] = l;
    }
    const auto elapsed = Util::getTimeNS() - t0;
    ret["elapsed"] = QString::number(elapsed/1e6, 'f', 6) + " msec";
    return ret;
}

size_t Controller::nBlocksDownloadedSoFar() const
{
    size_t ret = 0;
    for (const auto & [task, ign] : tasks) {
        Q_UNUSED(ign)
        auto t = dynamic_cast<DownloadBlocksTask *>(task);
        if (t)
            ret += t->nSoFar();
    }
    return ret;
}

std::tuple<size_t, size_t, size_t> Controller::nTxInOutSoFar() const
{
    size_t nTx = 0, nIn = 0, nOut = 0;
    for (const auto & [task, ign] : tasks) {
        Q_UNUSED(ign)
        auto t = dynamic_cast<DownloadBlocksTask *>(task);
        if (t) {
            nTx += t->nTx;
            nIn += t->nIns;
            nOut += t->nOuts;
        }
    }
    return {nTx, nIn, nOut};
}