#pragma once

#include <xrpl/beast/utility/Journal.h>

#include <atomic>
#include <memory>
#include <mutex>
#include <thread>

namespace xrpl {

class Application;

/** Manages load sources.

    This object creates an associated thread to maintain a clock.

    When the server is overloaded by a particular peer it issues a warning
    first. This allows friendly peers to reduce their consumption of resources,
    or disconnect from the server.

    The warning system is used instead of merely dropping, because hostile
    peers can just reconnect anyway.
*/
class LoadManager
{
    LoadManager(Application& app, beast::Journal journal);

public:
    LoadManager() = delete;
    LoadManager(LoadManager const&) = delete;
    LoadManager&
    operator=(LoadManager const&) = delete;

    /** Destroy the manager.

        The destructor returns only after the thread has stopped.
    */
    ~LoadManager();

    /** Turn on stall detection.

        The stall detector begins in a disabled state. After this function
        is called, it will report stalls using a separate thread whenever
        the reset function is not called at least once per 10 seconds.

        @see resetStallDetector
    */
    // VFALCO NOTE it seems that the stall detector has an "armed" state
    //             to prevent it from going off during program startup if
    //             there's a lengthy initialization operation taking place?
    //
    void
    activateStallDetector();

    /** Reset the stall detection timer.

        A dedicated thread monitors the stall timer, and if too much
        time passes it will produce log warnings.
    */
    void
    heartbeat();

    //--------------------------------------------------------------------------

    void
    start();

    void
    stop();

private:
    void
    run();

private:
    Application& app_;
    beast::Journal const journal_;

    std::thread thread_;
    std::mutex mutex_;  // Guards lastHeartbeat_, armed_, cv_
    std::condition_variable cv_;
    bool stop_ = false;

    // Detect server stalls
    std::chrono::steady_clock::time_point lastHeartbeat_;
    bool armed_;

    friend std::unique_ptr<LoadManager>
    make_LoadManager(Application& app, beast::Journal journal);
};

std::unique_ptr<LoadManager>
make_LoadManager(Application& app, beast::Journal journal);

}  // namespace xrpl
