ObsidianDragon/src/rpc/long_call_lane.h

// DragonX Wallet - ImGui Edition
// Copyright 2024-2026 The Hush Developers
// Released under the GPLv3

#pragma once

// Long wallet RPCs (C61). A rescan or a key import holds the daemon's cs_main for as long as the wallet scan
// takes: minutes to hours on a big wallet. On the shared clients they used to hit the 30 s curl timeout, report
// a failure that wasn't one and flip the app into "node busy" (a reply timeout is recorded by the busy gate).
// They now run one at a time on a dedicated, ungated client with no client timeout, abortable from any thread.

#include "connection.h"   // ConnectionConfig
#include "rpc_client.h"

#include <atomic>
#include <mutex>
#include <string>

namespace dragonx {
namespace rpc {

// The wallet RPCs that scan the chain inside the call: they run on the long-call lane, never on the shared
// clients (rpc_ / the console's fast lane), whose 30 s timeout they outlast.
inline bool isLongWalletMethod(const std::string& method)
{
    return method == "rescan" || method == "importprivkey" || method == "importaddress" ||
           method == "importwallet" || method == "z_importkey" || method == "z_importviewingkey" ||
           method == "z_importwallet";
}

// How a long wallet call that threw an RpcTransportError ended, which picks the wording shown to the user.
enum class LongCallCutOff {
    None,          // the request never reached the node: its error is the whole story
    Cancelled,     // our own abort cut the transfer; the node may still be scanning
    Interrupted,   // the request was sent but no answer came back (a dropped connection, or a proxy's 502/504
                   // while the node still runs it): the key may already be in the wallet
    Refused,       // the node's HTTP layer turned it away before the method ran (401, 503, queue full,
                   // unhandled), so nothing was imported
};

inline LongCallCutOff classifyLongCallCutOff(RpcFailureKind kind, bool requestSent)
{
    switch (kind) {
    case RpcFailureKind::Aborted:
        return LongCallCutOff::Cancelled;
    case RpcFailureKind::Auth:
    case RpcFailureKind::ShuttingDown:
    case RpcFailureKind::QueueFull:
    case RpcFailureKind::Unhandled:
        return LongCallCutOff::Refused;
    default:
        // Any other HTTP status (a proxy's 502/504) or a lost reply proves nothing about the node's side.
        return requestSent ? LongCallCutOff::Interrupted : LongCallCutOff::None;
    }
}

// One long wallet RPC at a time on its own ungated client, with no client timeout, abortable from any thread.
class LongCallLane {
public:
    // Main thread: claim the lane. false when a long call is already running. A new call starts un-aborted.
    bool tryBegin()
    {
        bool idle = false;
        if (!active_.compare_exchange_strong(idle, true)) return false;
        abort_ = false;
        return true;
    }
    // The call and its continuation are done: the lane is free again.
    void end() { active_ = false; }
    bool active() const { return active_.load(); }
    bool aborted() const { return abort_.load(); }

    // Any thread. Sticky until the next tryBegin(): a call that has not opened its client yet is aborted as soon
    // as it does, and an in-flight transfer is cut through the client's progress callback (about a second).
    void abort()
    {
        std::lock_guard<std::mutex> lk(mx_);
        abort_ = true;
        if (client_) client_->requestAbort();
    }

    // Lane thread. open() FIRST (it clears the client's abort flag), THEN publish the client, THEN re-check the
    // sticky flag under the same mutex, so an abort that landed before or during open() is never erased.
    // An open() failure is not handled here: the body's first call then throws "Not connected".
    template <class Body>
    void run(RPCClient& c, const ConnectionConfig& cfg, Body&& body)
    {
        c.open(cfg.host, cfg.port, cfg.rpcuser, cfg.rpcpassword, cfg.use_tls);
        {
            std::lock_guard<std::mutex> lk(mx_);
            client_ = &c;
            if (abort_) c.requestAbort();
        }
        struct Unpublish {
            LongCallLane& lane;
            ~Unpublish()
            {
                std::lock_guard<std::mutex> lk(lane.mx_);
                lane.client_ = nullptr;
            }
        } unpublish{*this};
        body(c);
    }

private:
    std::mutex mx_;
    RPCClient* client_ = nullptr;   // guarded by mx_; set only while run() executes the body
    std::atomic<bool> abort_{false};
    std::atomic<bool> active_{false};
};

} // namespace rpc
} // namespace dragonx