#ifndef STREAMFSM_H
#define STREAMFSM_H

#include <QObject>
#include <QProcess>
#include <QString>
#include <QStringList>
#include <functional>

/// A formal 2-state FSM wrapping a QProcess streaming lifecycle.
///
/// States: Idle ──start()──→ Running ──stop()──→ Idle
///                            Running ──process exit──→ Idle ──[policy]──→ Running | emit died()
///
/// Three restart policies:
///   Oneshot  — process runs once, then emits died()
///   Looping  — process always restarts after exit
///   Guarded  — process restarts only if guard() returns true
///
/// All signal connections are managed internally. stop() is safe to call
/// from any state; it disconnects before killing to prevent spurious signals.
class StreamFsm : public QObject
{
    Q_OBJECT
public:
    enum State { Idle, Running };
    enum RestartPolicy { Oneshot, Looping, Guarded };

    explicit StreamFsm(RestartPolicy policy, QObject *parent = nullptr);
    ~StreamFsm();

    State state() const { return m_state; }
    RestartPolicy policy() const { return m_policy; }

    /// Store program/args and start the process (no-op if already Running).
    void start(const QString &program, const QStringList &args);

    /// Kill the process and transition to Idle. Does not emit died().
    void stop();

    /// Guard predicate for Guarded policy — called after exit to decide
    /// whether to restart. Not used for Oneshot or Looping.
    void setGuard(std::function<bool()> guard);

signals:
    /// Emitted with data from the process's stdout (partial reads).
    void readyRead(const QByteArray &data);

    /// Emitted when the process has exited and will NOT be restarted
    /// (Oneshot policy, or Guarded policy with a false guard).
    void died();

private slots:
    void onReadyRead();
    void onFinished(int exitCode, QProcess::ExitStatus status);

private:
    void startProcess();
    void transitTo(State s);

    State m_state = Idle;
    QProcess *m_proc = nullptr;
    RestartPolicy m_policy;
    std::function<bool()> m_guard;
    QString m_program;
    QStringList m_args;
};

#endif // STREAMFSM_H