GPSCorrectionSelector.h

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#pragma once
 
#include <array>
#include <chrono>
#include <optional>
 
#include <QtCore/QString>
#include <QtQmlIntegration/QtQmlIntegration>
 
#include "GPSCorrectionSettings.h"
 
// HighestPriority, the automatic routing setting, names no specific source; it never carries corrections.
inline constexpr int GPS_CORRECTION_SOURCE_COUNT = static_cast<int>(GPSCorrectionSettings::Udp) + 1;
 
struct GPSCorrectionStream
{
    Q_GADGET
    QML_VALUE_TYPE(gpsCorrectionStream)
    QML_STRUCTURED_VALUE
    Q_PROPERTY(int source MEMBER source FINAL)
    Q_PROPERTY(QString instanceId MEMBER instanceId FINAL)
 
public:
    int source = 0;
    QString instanceId;
 
    bool operator==(const GPSCorrectionStream&) const = default;
};
 
class GPSCorrectionSelector
{
public:
    void configure(GPSCorrectionSettings::CorrectionSource source, qint64 now);
 
    void beginSource(GPSCorrectionSettings::CorrectionSource source, qint64 now);
    void endSource(GPSCorrectionSettings::CorrectionSource source, qint64 now);
    bool submit(GPSCorrectionSettings::CorrectionSource source, const QString& instance, qint64 receivedAtMs,
                qint64 now);
    void shutdown();
 
    bool hasSources() const;
 
    std::optional<GPSCorrectionStream> selectedStream(qint64 now) const;
 
    static constexpr std::chrono::milliseconds FRESHNESS_TIMEOUT{5000};
    static constexpr std::chrono::milliseconds SWITCH_HOLD_DOWN{2000};
 
private:
    struct Category
    {
        bool begun = false;
        QString instance{};
        qint64 lastRoutableMs = 0;
    };
 
    static int _index(GPSCorrectionSettings::CorrectionSource source);
    bool _fresh(const Category& category, qint64 now) const;
    bool _eligible(int index, qint64 now) const;
    void _select(qint64 now);
 
    GPSCorrectionSettings::CorrectionSource _configuredSource = GPSCorrectionSettings::HighestPriority;
    std::array<Category, GPS_CORRECTION_SOURCE_COUNT> _categories{};
    int _active = -1;
    int _candidate = -1;
    qint64 _candidateSinceMs = 0;
    bool _shutdown = false;
};