GPSSourceHealth.h

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#pragma once
 
#include <chrono>
#include <optional>
 
#include <QtCore/QObject>
 
#include "GPSObservation.h"
#include "ScheduledTask.h"
 
class GPSSourceHealth : public QObject
{
    Q_OBJECT
    friend class GPSSourceHealthTest;
    friend class PositionManagerTest;
 
public:
    enum class State
    {
        NoData = 0,
        Usable = 1,
        Invalid = 2,
        Stale = 3,
    };
    Q_ENUM(State)
 
    explicit GPSSourceHealth(QObject* parent = nullptr, RuntimeScheduler* scheduler = nullptr);
    ~GPSSourceHealth() override;
 
    static constexpr std::chrono::milliseconds FRESHNESS_TIMEOUT{5000};
 
    void setFreshnessTimeout(std::chrono::milliseconds timeout);
 
    State state() const { return _position.state; }
 
    quint64 observationRevision() const { return _observationRevision; }
 
    std::optional<GPSObservation> acceptedObservation(
        GPSObservation::PositionUse use = GPSObservation::PositionUse::GroundStation,
        std::optional<std::chrono::milliseconds> maximumAge = std::nullopt) const;
 
    void updateObservation(const GPSObservation& observation);
    void invalidatePosition();
    void reset();
 
signals:
    void positionChanged();
 
private:
    GPSObservation _observation() const { return _position.observation; }
 
    void _logStateChange(State previous) const;
    void _setState(State state);
    State _updatedPositionState() const;
    void _schedulePositionExpiry();
    std::optional<std::chrono::milliseconds> _age(quint64 timestampUs) const;
    std::chrono::microseconds _remaining(quint64 timestampUs,
                                         std::optional<std::chrono::milliseconds> maximumAge = std::nullopt) const;
 
    struct PositionState
    {
        GPSObservation observation;
        State state = State::NoData;
        bool invalidated = true;
    };
 
    std::chrono::milliseconds _freshnessTimeout = FRESHNESS_TIMEOUT;
    PositionState _position;
    RuntimeScheduler* const _scheduler;
    ScheduledTask _positionTask;
    quint64 _observationRevision = 0;
};