php-qml/framework/qml/src/BackendConnection.h

#pragma once

#include <QElapsedTimer>
#include <QObject>
#include <QString>
#include <QtQmlIntegration>

class QNetworkAccessManager;
class QNetworkReply;
class QTimer;
class QQmlEngine;
class QJSEngine;

namespace PhpQml::Bridge {

/// Owns the backend lifecycle and exposes its health to QML.
///
/// Phase 1 implements **dev mode**: reads `BRIDGE_URL` and `BRIDGE_TOKEN`
/// from env, periodically probes `<url>/healthz`, and reports the result
/// as `connectionState`. Bundled mode (spawning FrankenPHP as a child)
/// arrives in Phase 4. See PLAN.md §3 (Run modes), §7 (BackendConnection).
class BackendConnection : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    QML_SINGLETON

    Q_PROPERTY(Mode mode READ mode CONSTANT)
    Q_PROPERTY(QString url READ url CONSTANT)
    Q_PROPERTY(QString token READ token NOTIFY tokenChanged)
    Q_PROPERTY(ConnectionState connectionState READ connectionState NOTIFY connectionStateChanged)
    Q_PROPERTY(QString error READ error NOTIFY errorChanged)

public:
    enum class Mode {
        Dev,
        Bundled,  // Phase 4
    };
    Q_ENUM(Mode)

    /// Full Update Semantics enum (PLAN.md §5).
    ///   - Connecting   : initial state until first probe response
    ///   - Online       : last probe succeeded
    ///   - Reconnecting : ≥1 probe failed since last success; backing off
    ///   - Offline      : reconnect failures exceeded the threshold (default 30 s)
    enum class ConnectionState {
        Connecting,
        Online,
        Reconnecting,
        Offline,
    };
    Q_ENUM(ConnectionState)

    explicit BackendConnection(QObject* parent = nullptr);
    ~BackendConnection() override;

    static BackendConnection* create(QQmlEngine* engine, QJSEngine*);

    Mode mode() const noexcept { return m_mode; }
    QString url() const { return m_url; }
    QString token() const { return m_token; }
    ConnectionState connectionState() const noexcept { return m_state; }
    QString error() const { return m_error; }

    Q_INVOKABLE void restart();

signals:
    void tokenChanged();
    void connectionStateChanged();
    void errorChanged();
    /// Forward-compatible signal for §3 *Edge cases — Per-session secret
    /// rotation*. In Phase 1 dev mode it is never emitted; bundled mode
    /// in Phase 4 will fire it on child restart.
    void tokenRotated(const QString& newToken);

private slots:
    void probe();
    void onProbeFinished();

private:
    void setState(ConnectionState s);
    void setError(const QString& msg);

    Mode m_mode = Mode::Dev;
    QString m_url;
    QString m_token;
    ConnectionState m_state = ConnectionState::Connecting;
    QString m_error;

    QNetworkAccessManager* m_nam = nullptr;
    QNetworkReply* m_pendingReply = nullptr;
    QTimer* m_retryTimer = nullptr;
    QElapsedTimer m_firstFailureSinceOnline;  // not started while Online
    int m_offlineThresholdMs = 30000;
};

} // namespace PhpQml::Bridge