#include "streamfsm.h"

StreamFsm::StreamFsm(RestartPolicy policy, QObject *parent)
    : QObject(parent)
    , m_policy(policy)
{
}

StreamFsm::~StreamFsm()
{
    stop();
}

void StreamFsm::start(const QString &program, const QStringList &args)
{
    m_program = program;
    m_args = args;
    if (m_state == Idle)
        startProcess();
}

void StreamFsm::stop()
{
    if (m_state == Idle)
        return;

    if (m_proc) {
        // Disconnect before killing so onFinished doesn't fire during teardown.
        m_proc->disconnect();
        m_proc->kill();
        m_proc->waitForFinished(1000);
        m_proc->deleteLater();
        m_proc = nullptr;
    }
    transitTo(Idle);
}

void StreamFsm::setGuard(std::function<bool()> guard)
{
    m_guard = std::move(guard);
}

void StreamFsm::startProcess()
{
    if (m_state != Idle)
        return;

    m_proc = new QProcess(this);
    connect(m_proc, &QProcess::readyReadStandardOutput,
            this, &StreamFsm::onReadyRead);
    connect(m_proc,
            QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
            this, &StreamFsm::onFinished);
    m_proc->start(m_program, m_args);
    transitTo(Running);
}

void StreamFsm::onReadyRead()
{
    QByteArray data = m_proc->readAllStandardOutput();
    if (!data.isEmpty())
        emit readyRead(data);
}

void StreamFsm::onFinished(int, QProcess::ExitStatus)
{
    // Clean up the finished process.
    m_proc->deleteLater();
    m_proc = nullptr;
    transitTo(Idle);

    // Decide what to do next based on policy.
    switch (m_policy) {
    case Oneshot:
        emit died();
        break;
    case Looping:
        startProcess();
        break;
    case Guarded:
        if (m_guard && m_guard())
            startProcess();
        else
            emit died();
        break;
    }
}

void StreamFsm::transitTo(State s)
{
    m_state = s;
}