#include "BackendConnection.h"

#include <QCoreApplication>
#include <QDebug>
#include <QDir>
#include <QFileInfo>
#include <QLoggingCategory>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QProcessEnvironment>
#include <QQmlEngine>
#include <QRandomGenerator>
#include <QStandardPaths>
#include <QTimer>
#include <QUrl>

#include <csignal>
#include <sys/prctl.h>

namespace PhpQml::Bridge {

Q_LOGGING_CATEGORY(lcBundled, "phpqml.bridge.bundled")

namespace {
constexpr int kInitialProbeMs   = 0;
constexpr int kProbeIntervalMs  = 5000;
constexpr int kProbeTimeoutMs   = 2000;
constexpr int kMigrateTimeoutMs = 60000;
constexpr int kBootProbeMaxMs   = 10000;
} // namespace

BackendConnection::BackendConnection(QObject* parent)
    : QObject(parent)
    , m_appName(QCoreApplication::applicationName().isEmpty()
                ? QStringLiteral("php-qml-app")
                : QCoreApplication::applicationName())
    , m_nam(new QNetworkAccessManager(this))
    , m_retryTimer(new QTimer(this))
{
    m_retryTimer->setSingleShot(false);
    m_retryTimer->setInterval(kProbeIntervalMs);
    connect(m_retryTimer, &QTimer::timeout, this, &BackendConnection::probe);

    // aboutToQuit fires while the event loop is still active, before main()
    // starts unwinding the stack. Without this, teardownChild only runs from
    // ~BackendConnection — by then the QQmlEngine is already mid-destruction
    // and Qt warns "QProcess: Destroyed while process is still running".
    if (QCoreApplication::instance()) {
        connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit,
                this, &BackendConnection::teardownChild);
    }

    const QString explicitUrl = QString::fromUtf8(qgetenv("BRIDGE_URL"));
    if (!explicitUrl.isEmpty()) {
        m_mode = Mode::Dev;
        m_url  = explicitUrl;
        m_token = QString::fromUtf8(qgetenv("BRIDGE_TOKEN"));
        QTimer::singleShot(0, this, &BackendConnection::initDevMode);
    } else {
        m_mode = Mode::Bundled;
        // Bundled init runs after the QApplication event loop is up so
        // QStandardPaths and QProcess work correctly.
        QTimer::singleShot(0, this, &BackendConnection::initBundledMode);
    }
}

BackendConnection::~BackendConnection()
{
    teardownChild();
}

BackendConnection* BackendConnection::create(QQmlEngine* engine, QJSEngine*)
{
    return new BackendConnection(engine);
}

void BackendConnection::initDevMode()
{
    if (m_url.isEmpty()) {
        m_url = QStringLiteral("http://127.0.0.1:8765");
    }
    emit urlChanged();
    QTimer::singleShot(kInitialProbeMs, this, &BackendConnection::probe);
    m_retryTimer->start();
}

void BackendConnection::initBundledMode()
{
    const QString fpBin    = resolveFrankenphpBin();
    const QString symfony  = resolveSymfonyDir();
    const QString caddyCfg = resolveCaddyfilePath();

    if (!QFileInfo(fpBin).isExecutable()) {
        const QString msg = QStringLiteral("bundled: frankenphp not found at %1 (override with BRIDGE_FRANKENPHP_BIN)").arg(fpBin);
        qCWarning(lcBundled) << msg;
        setError(msg);
        setState(ConnectionState::Offline);
        return;
    }
    if (symfony.isEmpty() || !QFileInfo(symfony + "/public/index.php").exists()) {
        const QString msg = QStringLiteral("bundled: symfony app not found near %1 (override with BRIDGE_SYMFONY_DIR)").arg(QCoreApplication::applicationDirPath());
        qCWarning(lcBundled) << msg;
        setError(msg);
        setState(ConnectionState::Offline);
        return;
    }
    if (caddyCfg.isEmpty() || !QFileInfo(caddyCfg).exists()) {
        const QString msg = QStringLiteral("bundled: Caddyfile not found near %1 (override with BRIDGE_CADDYFILE)").arg(QCoreApplication::applicationDirPath());
        qCWarning(lcBundled) << msg;
        setError(msg);
        setState(ConnectionState::Offline);
        return;
    }
    qCInfo(lcBundled) << "frankenphp:" << fpBin;
    qCInfo(lcBundled) << "symfony:"    << symfony;
    qCInfo(lcBundled) << "caddyfile:"  << caddyCfg;

    m_dataDir = userDataDir();
    QDir().mkpath(m_dataDir + "/var/log");
    // Wipe Symfony cache: kernel.project_dir bakes the AppImage FUSE mount path
    // (different every launch), so cache from a previous launch is always stale.
    QDir(m_dataDir + "/var/cache").removeRecursively();
    QDir().mkpath(m_dataDir + "/var/cache");

    setToken(randomSecret(32));
    m_jwtSecret = randomSecret(48);  // ≥256 bits for lcobucci/jwt
    setUrl(QStringLiteral("http://127.0.0.1:%1").arg(m_port));

    if (!runMigrations()) {
        return;  // setError already invoked
    }

    QString spawnErr;
    if (!spawnChild(&spawnErr)) {
        setError(spawnErr);
        setState(ConnectionState::Offline);
        return;
    }

    setState(ConnectionState::Connecting);
    QTimer::singleShot(kInitialProbeMs, this, &BackendConnection::probe);
    m_retryTimer->start();
}

QString BackendConnection::resolveFrankenphpBin() const
{
    const QByteArray override = qgetenv("BRIDGE_FRANKENPHP_BIN");
    if (!override.isEmpty()) return QString::fromUtf8(override);
    // build-appimage.sh installs frankenphp as a sibling of the host binary at usr/bin/frankenphp.
    return QCoreApplication::applicationDirPath() + QStringLiteral("/frankenphp");
}

QString BackendConnection::resolveSymfonyDir() const
{
    const QByteArray override = qgetenv("BRIDGE_SYMFONY_DIR");
    if (!override.isEmpty()) return QString::fromUtf8(override);

    const QString here = QCoreApplication::applicationDirPath();
    const QStringList candidates = {
        here + QStringLiteral("/symfony"),
        here + QStringLiteral("/../symfony"),
        here + QStringLiteral("/../share/") + m_appName + QStringLiteral("/symfony"),
        here + QStringLiteral("/../usr/share/") + m_appName + QStringLiteral("/symfony"),
    };
    for (const QString& c : candidates) {
        if (QFileInfo(c + "/public/index.php").exists()) {
            return QDir(c).absolutePath();
        }
    }
    return {};
}

QString BackendConnection::resolveCaddyfilePath() const
{
    const QByteArray override = qgetenv("BRIDGE_CADDYFILE");
    if (!override.isEmpty()) return QString::fromUtf8(override);

    const QString here = QCoreApplication::applicationDirPath();
    const QStringList candidates = {
        here + QStringLiteral("/Caddyfile"),
        here + QStringLiteral("/../Caddyfile"),
        here + QStringLiteral("/../share/") + m_appName + QStringLiteral("/Caddyfile"),
        here + QStringLiteral("/../usr/share/") + m_appName + QStringLiteral("/Caddyfile"),
    };
    for (const QString& c : candidates) {
        if (QFileInfo(c).exists()) {
            return QFileInfo(c).absoluteFilePath();
        }
    }
    return {};
}

QString BackendConnection::userDataDir() const
{
    QString p = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);
    if (p.isEmpty()) {
        p = QDir::homePath() + QStringLiteral("/.local/share/") + m_appName;
    }
    return p;
}

QString BackendConnection::databaseUrl() const
{
    return QStringLiteral("sqlite:///%1/var/data.sqlite").arg(m_dataDir);
}

bool BackendConnection::runMigrations()
{
    QProcess proc;
    proc.setProgram(resolveFrankenphpBin());
    proc.setArguments({
        QStringLiteral("php-cli"),
        resolveSymfonyDir() + QStringLiteral("/bin/console"),
        QStringLiteral("doctrine:migrations:migrate"),
        QStringLiteral("-n"),
    });

    // AppImage mount is read-only; redirect Symfony's writable dirs into the
    // user data dir (Kernel::getCacheDir/getLogDir read these env vars).
    const QString cacheDir = m_dataDir + QStringLiteral("/var/cache");
    const QString logDir   = m_dataDir + QStringLiteral("/var/log");
    QDir().mkpath(cacheDir);
    QDir().mkpath(logDir);

    QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
    env.insert(QStringLiteral("APP_ENV"),       QStringLiteral("prod"));
    env.insert(QStringLiteral("APP_DEBUG"),     QStringLiteral("0"));
    env.insert(QStringLiteral("APP_SECRET"),    QStringLiteral("bundled-mode-migrations-do-not-need-this"));
    env.insert(QStringLiteral("DATABASE_URL"),  databaseUrl());
    env.insert(QStringLiteral("APP_CACHE_DIR"), cacheDir);
    env.insert(QStringLiteral("APP_LOG_DIR"),   logDir);
    proc.setProcessEnvironment(env);
    proc.setWorkingDirectory(resolveSymfonyDir());
    proc.setProcessChannelMode(QProcess::MergedChannels);

    qCInfo(lcBundled) << "running migrations against" << databaseUrl();
    proc.start();
    if (!proc.waitForFinished(kMigrateTimeoutMs)) {
        proc.kill();
        const QString msg = QStringLiteral("bundled: migrations timed out");
        qCWarning(lcBundled) << msg;
        setError(msg);
        setState(ConnectionState::Offline);
        return false;
    }
    if (proc.exitStatus() != QProcess::NormalExit || proc.exitCode() != 0) {
        const QString msg = QStringLiteral("bundled: migrations failed (exit %1)\n%2")
            .arg(proc.exitCode())
            .arg(QString::fromUtf8(proc.readAll()));
        qCWarning(lcBundled).noquote() << msg;
        setError(msg);
        setState(ConnectionState::Offline);
        return false;
    }
    qCInfo(lcBundled) << "migrations OK";
    return true;
}

bool BackendConnection::spawnChild(QString* errorOut)
{
    teardownChild();

    m_child = new QProcess(this);
    m_child->setProgram(resolveFrankenphpBin());
    m_child->setArguments({
        QStringLiteral("run"),
        QStringLiteral("--config"),
        resolveCaddyfilePath(),
    });
    m_child->setWorkingDirectory(resolveSymfonyDir());

    // AppImage mount is read-only; redirect Symfony's writable dirs into the
    // user data dir (Kernel::getCacheDir/getLogDir read these env vars).
    const QString cacheDir = m_dataDir + QStringLiteral("/var/cache");
    const QString logDir   = m_dataDir + QStringLiteral("/var/log");
    QDir().mkpath(cacheDir);
    QDir().mkpath(logDir);

    QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
    env.insert(QStringLiteral("APP_ENV"),       QStringLiteral("prod"));
    env.insert(QStringLiteral("APP_DEBUG"),     QStringLiteral("0"));
    env.insert(QStringLiteral("APP_SECRET"),    randomSecret(16));
    env.insert(QStringLiteral("BRIDGE_TOKEN"),  m_token);
    env.insert(QStringLiteral("DATABASE_URL"),  databaseUrl());
    env.insert(QStringLiteral("APP_CACHE_DIR"), cacheDir);
    env.insert(QStringLiteral("APP_LOG_DIR"),   logDir);
    env.insert(QStringLiteral("PORT"),          QString::number(m_port));
    env.insert(QStringLiteral("MERCURE_URL"),         m_url + QStringLiteral("/.well-known/mercure"));
    env.insert(QStringLiteral("MERCURE_PUBLIC_URL"),  m_url + QStringLiteral("/.well-known/mercure"));
    env.insert(QStringLiteral("MERCURE_JWT_SECRET"),         m_jwtSecret);
    env.insert(QStringLiteral("MERCURE_PUBLISHER_JWT_KEY"),  m_jwtSecret);
    env.insert(QStringLiteral("MERCURE_SUBSCRIBER_JWT_KEY"), m_jwtSecret);
    m_child->setProcessEnvironment(env);
    // Capture both streams into a single chronological buffer so the
    // DevConsole sees stderr (FrankenPHP / Symfony logs) interleaved with
    // stdout the same way a TTY would. The console keeps still emitting
    // each line via qCInfo(lcBundled) so terminal users aren't blinded.
    m_child->setProcessChannelMode(QProcess::MergedChannels);

    // Linux: kernel kills the child if the parent dies for any reason.
    m_child->setChildProcessModifier([] {
        prctl(PR_SET_PDEATHSIG, SIGTERM);
    });

    connect(m_child, &QProcess::finished,
            this, &BackendConnection::onChildFinished);
    connect(m_child, &QProcess::readyReadStandardOutput,
            this, &BackendConnection::onChildOutputReady);

    qCInfo(lcBundled) << "spawning frankenphp on port" << m_port;
    m_child->start();
    if (!m_child->waitForStarted(5000)) {
        const QString err = QStringLiteral("bundled: failed to start frankenphp: ") + m_child->errorString();
        qCWarning(lcBundled) << err;
        if (errorOut) *errorOut = err;
        teardownChild();
        return false;
    }
    return true;
}

void BackendConnection::teardownChild()
{
    if (!m_child) return;
    if (m_child->state() != QProcess::NotRunning) {
        m_child->terminate();
        if (!m_child->waitForFinished(2000)) {
            m_child->kill();
            m_child->waitForFinished(1000);
        }
    }
    disconnect(m_child, nullptr, this, nullptr);
    m_child->deleteLater();
    m_child = nullptr;
    m_childLogBuffer.clear();
}

void BackendConnection::onChildOutputReady()
{
    if (!m_child) return;
    m_childLogBuffer += QString::fromUtf8(m_child->readAllStandardOutput());

    int nl;
    while ((nl = m_childLogBuffer.indexOf(QLatin1Char('\n'))) >= 0) {
        QString line = m_childLogBuffer.left(nl);
        m_childLogBuffer.remove(0, nl + 1);
        if (line.endsWith(QLatin1Char('\r'))) {
            line.chop(1);
        }
        qCInfo(lcBundled).noquote() << line;
        m_childLog.enqueue(line);
        while (m_childLog.size() > kChildLogMax) {
            m_childLog.dequeue();
        }
        emit childLogLine(line);
    }
}

QStringList BackendConnection::childLogTail() const
{
    QStringList out;
    out.reserve(m_childLog.size());
    for (const QString& l : m_childLog) {
        out.append(l);
    }
    return out;
}

void BackendConnection::onChildFinished(int exitCode, QProcess::ExitStatus status)
{
    Q_UNUSED(status);
    if (m_mode != Mode::Bundled) return;

    setError(QStringLiteral("bundled: frankenphp exited (code=%1); supervisor restart").arg(exitCode));

    if (m_supervisorRetries >= kMaxSupervisorRetries) {
        setState(ConnectionState::Offline);
        return;
    }
    ++m_supervisorRetries;

    // New session secret on every restart.
    setToken(randomSecret(32));
    emit tokenRotated(m_token);

    QString err;
    if (!spawnChild(&err)) {
        setError(err);
        setState(ConnectionState::Offline);
        return;
    }
    setState(ConnectionState::Reconnecting);
}

void BackendConnection::restart()
{
    if (m_mode == Mode::Bundled) {
        m_supervisorRetries = 0;
        QString err;
        if (!spawnChild(&err)) {
            setError(err);
            setState(ConnectionState::Offline);
            return;
        }
        setState(ConnectionState::Connecting);
    }
    probe();
}

void BackendConnection::probe()
{
    if (m_pendingReply) return;

    QNetworkRequest req;
    req.setUrl(QUrl(m_url + QStringLiteral("/healthz")));
    req.setTransferTimeout(kProbeTimeoutMs);
    if (!m_token.isEmpty()) {
        req.setRawHeader("Authorization", "Bearer " + m_token.toUtf8());
    }

    m_pendingReply = m_nam->get(req);
    connect(m_pendingReply, &QNetworkReply::finished,
            this, &BackendConnection::onProbeFinished);
}

void BackendConnection::onProbeFinished()
{
    QNetworkReply* reply = m_pendingReply;
    m_pendingReply = nullptr;
    if (!reply) return;
    reply->deleteLater();

    bool ok = false;
    if (reply->error() == QNetworkReply::NoError) {
        const int status = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
        if (status == 200) {
            ok = true;
        } else {
            setError(QStringLiteral("/healthz returned HTTP %1").arg(status));
        }
    } else {
        setError(reply->errorString());
    }

    if (ok) {
        setError(QString());
        m_firstFailureSinceOnline.invalidate();
        m_supervisorRetries = 0;
        setState(ConnectionState::Online);
        return;
    }

    if (!m_firstFailureSinceOnline.isValid()) {
        m_firstFailureSinceOnline.start();
    }

    // In bundled mode, ride the supervisor: hint Reconnecting until the
    // child re-spawns or we exhaust retries (which sets Offline directly).
    const int boot = (m_mode == Mode::Bundled) ? kBootProbeMaxMs : 0;
    if (m_firstFailureSinceOnline.hasExpired(m_offlineThresholdMs + boot)) {
        setState(ConnectionState::Offline);
    } else {
        setState(ConnectionState::Reconnecting);
    }
}

void BackendConnection::setState(ConnectionState s)
{
    if (m_state == s) return;
    m_state = s;
    emit connectionStateChanged();
}

void BackendConnection::setError(const QString& msg)
{
    if (m_error == msg) return;
    m_error = msg;
    emit errorChanged();
}

void BackendConnection::setUrl(const QString& url)
{
    if (m_url == url) return;
    m_url = url;
    emit urlChanged();
}

void BackendConnection::setToken(const QString& token)
{
    if (m_token == token) return;
    m_token = token;
    emit tokenChanged();
}

QString BackendConnection::randomSecret(int bytes)
{
    QByteArray buf(bytes, Qt::Uninitialized);
    auto* gen = QRandomGenerator::system();
    gen->generate(buf.begin(), buf.end());
    return QString::fromLatin1(buf.toBase64(QByteArray::Base64UrlEncoding | QByteArray::OmitTrailingEquals));
}

QString BackendConnection::resolveSidecarUpdater() const
{
    const QByteArray override = qgetenv("BRIDGE_APPIMAGEUPDATE_BIN");
    if (!override.isEmpty()) return QString::fromUtf8(override);
    return QCoreApplication::applicationDirPath() + QStringLiteral("/AppImageUpdate.AppImage");
}

QString BackendConnection::currentAppImagePath() const
{
    // The AppImage runtime exports APPIMAGE pointing at the on-disk
    // AppImage that's currently running. Outside an AppImage this is
    // empty — bundled-mode-via-loose-files can't auto-update yet.
    return QString::fromUtf8(qgetenv("APPIMAGE"));
}

void BackendConnection::checkForUpdates()
{
    if (m_mode != Mode::Bundled) {
        emit updateCheckFailed(QStringLiteral("update checks are bundled-mode only"));
        return;
    }
    if (m_updateCheck && m_updateCheck->state() != QProcess::NotRunning) {
        return;  // already in flight
    }
    const QString sidecar = resolveSidecarUpdater();
    if (!QFileInfo(sidecar).isExecutable()) {
        emit updateCheckFailed(QStringLiteral("AppImageUpdate sidecar not found at %1").arg(sidecar));
        return;
    }
    const QString appImage = currentAppImagePath();
    if (appImage.isEmpty()) {
        emit updateCheckFailed(QStringLiteral("APPIMAGE env not set; not running from a packaged AppImage"));
        return;
    }

    if (m_updateCheck) m_updateCheck->deleteLater();
    m_updateCheck = new QProcess(this);
    m_updateCheck->setProgram(sidecar);
    // appimageupdatetool exit codes: 0 = no update, 1 = update available,
    // anything else = error. The sidecar AppImage forwards to that tool.
    m_updateCheck->setArguments({QStringLiteral("--check-for-update"), appImage});
    m_updateCheck->setProcessChannelMode(QProcess::MergedChannels);
    connect(m_updateCheck, &QProcess::finished,
            this, &BackendConnection::onUpdateCheckFinished);
    m_updateCheck->start();
}

void BackendConnection::onUpdateCheckFinished(int exitCode, QProcess::ExitStatus status)
{
    Q_UNUSED(status);
    if (!m_updateCheck) return;
    const QByteArray out = m_updateCheck->readAll();
    m_updateCheck->deleteLater();
    m_updateCheck = nullptr;

    if (exitCode == 0) {
        emit noUpdatesAvailable();
    } else if (exitCode == 1) {
        emit updatesAvailable();
    } else {
        emit updateCheckFailed(QStringLiteral("AppImageUpdate exited %1: %2")
                               .arg(exitCode)
                               .arg(QString::fromUtf8(out).trimmed()));
    }
}

void BackendConnection::applyUpdate()
{
    if (m_mode != Mode::Bundled) {
        emit updateApplyFailed(QStringLiteral("update apply is bundled-mode only"));
        return;
    }
    if (m_updateApply && m_updateApply->state() != QProcess::NotRunning) {
        return;
    }
    const QString sidecar = resolveSidecarUpdater();
    if (!QFileInfo(sidecar).isExecutable()) {
        emit updateApplyFailed(QStringLiteral("AppImageUpdate sidecar not found at %1").arg(sidecar));
        return;
    }
    const QString appImage = currentAppImagePath();
    if (appImage.isEmpty()) {
        emit updateApplyFailed(QStringLiteral("APPIMAGE env not set; not running from a packaged AppImage"));
        return;
    }

    if (m_updateApply) m_updateApply->deleteLater();
    m_updateApply = new QProcess(this);
    m_updateApply->setProgram(sidecar);
    m_updateApply->setArguments({QStringLiteral("--remove-old"), appImage});
    m_updateApply->setProcessChannelMode(QProcess::MergedChannels);
    connect(m_updateApply, &QProcess::finished,
            this, &BackendConnection::onUpdateApplyFinished);
    m_updateApply->start();
}

void BackendConnection::onUpdateApplyFinished(int exitCode, QProcess::ExitStatus status)
{
    Q_UNUSED(status);
    if (!m_updateApply) return;
    const QByteArray out = m_updateApply->readAll();
    m_updateApply->deleteLater();
    m_updateApply = nullptr;

    if (exitCode == 0) {
        emit updateApplied();
    } else {
        emit updateApplyFailed(QStringLiteral("AppImageUpdate exited %1: %2")
                               .arg(exitCode)
                               .arg(QString::fromUtf8(out).trimmed()));
    }
}

} // namespace PhpQml::Bridge