ObsidianDragon/src/rpc/rpc_worker.cpp

// DragonX Wallet - ImGui Edition
// Copyright 2024-2026 The Hush Developers
// Released under the GPLv3
//
// rpc_worker.cpp — Background work queue. Executes WorkFn on its own thread,
// returns MainCb callbacks drained each frame on the main thread.

#include "rpc_worker.h"
#include <cstdio>
#include "../util/logger.h"

namespace dragonx {
namespace rpc {

RPCWorker::RPCWorker() = default;

RPCWorker::~RPCWorker()
{
    stop();
}

void RPCWorker::start()
{
    if (running_.load(std::memory_order_relaxed)) return;

    running_.store(true, std::memory_order_release);
    thread_ = std::thread(&RPCWorker::run, this);
}

void RPCWorker::stop()
{
    if (!running_.load(std::memory_order_relaxed) && !thread_.joinable()) return;

    // Signal stop if not already signaled
    requestStop();

    if (thread_.joinable()) {
        thread_.join();
    }

    // Discard pending tasks
    {
        std::lock_guard<std::mutex> lk(taskMtx_);
        tasks_.clear();
    }
}

void RPCWorker::requestStop()
{
    if (!running_.load(std::memory_order_relaxed)) return;

    {
        std::lock_guard<std::mutex> lk(taskMtx_);
        running_.store(false, std::memory_order_release);
    }
    taskCv_.notify_one();
}

void RPCWorker::post(WorkFn work)
{
    {
        std::lock_guard<std::mutex> lk(taskMtx_);
        tasks_.push_back(std::move(work));
    }
    taskCv_.notify_one();
}

int RPCWorker::drainResults()
{
    // Swap the result queue under the lock, then execute outside the lock
    // to minimise contention with the worker thread.
    std::deque<MainCb> batch;
    {
        std::lock_guard<std::mutex> lk(resultMtx_);
        batch.swap(results_);
    }

    int count = 0;
    for (auto& cb : batch) {
        if (cb) {
            try {
                cb();
            } catch (const std::exception& e) {
                DEBUG_LOGF("[RPCWorker] Main-thread callback threw: %s\n", e.what());
            } catch (...) {
                DEBUG_LOGF("[RPCWorker] Main-thread callback threw unknown exception\n");
            }
            ++count;
        }
    }
    return count;
}

bool RPCWorker::hasPendingResults() const
{
    std::lock_guard<std::mutex> lk(resultMtx_);
    return !results_.empty();
}

std::size_t RPCWorker::pendingTaskCount() const
{
    std::lock_guard<std::mutex> lk(taskMtx_);
    return tasks_.size();
}

std::size_t RPCWorker::pendingResultCount() const
{
    std::lock_guard<std::mutex> lk(resultMtx_);
    return results_.size();
}

void RPCWorker::run()
{
    while (true) {
        WorkFn task;

        // Wait for a task or stop signal
        {
            std::unique_lock<std::mutex> lk(taskMtx_);
            taskCv_.wait(lk, [this] {
                return !tasks_.empty() || !running_.load(std::memory_order_acquire);
            });

            if (!running_.load(std::memory_order_acquire) && tasks_.empty()) {
                break;
            }

            if (!tasks_.empty()) {
                task = std::move(tasks_.front());
                tasks_.pop_front();
            }
        }

        if (!task) continue;

        // Execute the work function (blocking I/O happens here)
        try {
            MainCb result = task();
            if (result) {
                std::lock_guard<std::mutex> lk(resultMtx_);
                results_.push_back(std::move(result));
            }
        } catch (const std::exception& e) {
            DEBUG_LOGF("[RPCWorker] Task threw: %s\n", e.what());
        } catch (...) {
            // A raw post() job that throws still loses its MainCb (no worse than the
            // std::exception path); this only keeps the worker thread alive.
            DEBUG_LOGF("[RPCWorker] Task threw unknown exception\n");
        }
    }
}

} // namespace rpc
} // namespace dragonx