#include "ReactiveObject.h"

#include "MercureClient.h"

#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonValue>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QRandomGenerator>
#include <QTimer>
#include <QUrl>

namespace PhpQml::Bridge {

ReactiveObject::ReactiveObject(QObject* parent)
    : QObject(parent)
    , m_data(new QQmlPropertyMap(this))
    , m_nam(new QNetworkAccessManager(this))
    , m_mercure(new MercureClient(this))
{
    connect(m_mercure, &MercureClient::update,
            this, &ReactiveObject::onMercureUpdate);
}

ReactiveObject::~ReactiveObject()
{
    qDeleteAll(m_echoTimers);
}

void ReactiveObject::setBaseUrl(const QString& v)
{
    if (m_baseUrl == v) return;
    m_baseUrl = v;
    rewireMercure();
    emit baseUrlChanged();
    if (!m_source.isEmpty()) refresh();
}

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

void ReactiveObject::setSource(const QString& v)
{
    if (m_source == v) return;
    m_source = v;
    emit sourceChanged();
    if (!m_baseUrl.isEmpty()) refresh();
}

void ReactiveObject::setTopic(const QString& v)
{
    if (m_topic == v) return;
    m_topic = v;
    rewireMercure();
    emit topicChanged();
}

void ReactiveObject::rewireMercure()
{
    if (m_baseUrl.isEmpty() || m_topic.isEmpty()) return;
    m_mercure->stop();
    m_mercure->setHubUrl(m_baseUrl + QStringLiteral("/.well-known/mercure"));
    m_mercure->setTopic(m_topic);
    m_mercure->start();
}

void ReactiveObject::refresh()
{
    fetchInitial();
}

void ReactiveObject::fetchInitial()
{
    if (m_baseUrl.isEmpty() || m_source.isEmpty()) return;
    if (m_pendingFetch) {
        m_pendingFetch->abort();
        m_pendingFetch->deleteLater();
        m_pendingFetch = nullptr;
    }

    QNetworkRequest req(QUrl(m_baseUrl + m_source));
    req.setRawHeader("Accept", "application/json");
    if (!m_token.isEmpty()) {
        req.setRawHeader("Authorization", "Bearer " + m_token.toUtf8());
    }
    req.setTransferTimeout(5000);

    setReady(false);
    m_pendingFetch = m_nam->get(req);
    connect(m_pendingFetch, &QNetworkReply::finished,
            this, &ReactiveObject::onFetchFinished);
}

void ReactiveObject::onFetchFinished()
{
    QNetworkReply* reply = m_pendingFetch;
    m_pendingFetch = nullptr;
    if (!reply) return;
    reply->deleteLater();

    const int status = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
    if (reply->error() != QNetworkReply::NoError) {
        setError(reply->errorString());
        return;
    }
    if (status == 404) {
        clearData();
        setExists(false);
        setError(QString());
        setReady(true);
        return;
    }
    if (status < 200 || status >= 300) {
        setError(QStringLiteral("GET %1 returned HTTP %2").arg(m_source).arg(status));
        return;
    }

    QJsonParseError err{};
    const QJsonDocument doc = QJsonDocument::fromJson(reply->readAll(), &err);
    if (err.error != QJsonParseError::NoError || !doc.isObject()) {
        setError(QStringLiteral("Initial fetch did not return a JSON object."));
        return;
    }

    applyPayload(doc.object());
    setExists(true);
    setError(QString());
    setReady(true);
}

void ReactiveObject::onMercureUpdate(const QString& data, const QString& /*id*/)
{
    QJsonParseError err{};
    const QJsonDocument doc = QJsonDocument::fromJson(data.toUtf8(), &err);
    if (err.error != QJsonParseError::NoError || !doc.isObject()) return;
    const QJsonObject envelope = doc.object();

    const int version = envelope.value(QStringLiteral("version")).toInt();
    if (m_lastVersion > 0 && version > m_lastVersion + 1) {
        // gap — re-fetch to recover
        m_lastVersion = 0;
        refresh();
        return;
    }
    m_lastVersion = std::max(m_lastVersion, version);

    const QString op  = envelope.value(QStringLiteral("op")).toString();
    const QString key = envelope.value(QStringLiteral("correlationKey")).toString();

    if (op == QStringLiteral("delete")) {
        clearData();
        setExists(false);
    } else if (op == QStringLiteral("upsert") || op == QStringLiteral("replace")) {
        applyPayload(envelope.value(QStringLiteral("data")).toObject());
        setExists(true);
    }

    if (!key.isEmpty()) {
        const QByteArray k = key.toUtf8();
        if (m_inFlight.contains(k)) {
            m_inFlight.remove(k);
            if (auto* t = m_echoTimers.take(k)) t->deleteLater();
            if (m_inFlight.isEmpty()) setPending(false);
            emit commandSucceeded(key, {});
        }
    }
}

void ReactiveObject::applyPayload(const QJsonObject& payload)
{
    for (auto it = payload.constBegin(); it != payload.constEnd(); ++it) {
        m_data->insert(it.key(), it.value().toVariant());
    }
}

void ReactiveObject::clearData()
{
    const QStringList keys = m_data->keys();
    for (const QString& k : keys) {
        m_data->clear(k);
    }
}

void ReactiveObject::setReady(bool r)
{
    if (m_ready == r) return;
    m_ready = r;
    emit readyChanged();
}

void ReactiveObject::setPending(bool p)
{
    if (m_pending == p) return;
    m_pending = p;
    emit pendingChanged();
}

void ReactiveObject::setExists(bool e)
{
    if (m_exists == e) return;
    m_exists = e;
    emit existsChanged();
}

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

void ReactiveObject::invoke(const QString& method,
                            const QString& path,
                            const QVariant& body,
                            const QVariantMap& optimistic)
{
    if (m_baseUrl.isEmpty()) return;

    const QByteArray key = buildIdempotencyKey();

    InFlight in;
    for (auto it = optimistic.constBegin(); it != optimistic.constEnd(); ++it) {
        if (m_data->keys().contains(it.key())) {
            in.backup.insert(it.key(), m_data->value(it.key()));
        } else {
            in.addedKeys << it.key();
        }
        m_data->insert(it.key(), it.value());
    }
    m_inFlight.insert(key, in);
    setPending(true);

    QNetworkRequest req(QUrl(m_baseUrl + path));
    req.setRawHeader("Accept", "application/json");
    req.setRawHeader("Idempotency-Key", key);
    if (!m_token.isEmpty()) {
        req.setRawHeader("Authorization", "Bearer " + m_token.toUtf8());
    }

    QByteArray bytes;
    if (body.isValid() && !body.isNull()) {
        bytes = QJsonDocument(QJsonObject::fromVariantMap(body.toMap())).toJson(QJsonDocument::Compact);
        req.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");
    }

    QNetworkReply* reply = nullptr;
    if (method == QStringLiteral("POST")) {
        reply = m_nam->post(req, bytes);
    } else if (method == QStringLiteral("PATCH")) {
        reply = m_nam->sendCustomRequest(req, "PATCH", bytes);
    } else if (method == QStringLiteral("DELETE")) {
        reply = m_nam->deleteResource(req);
    } else {
        rollbackOptimistic(key);
        return;
    }
    m_replyToKey.insert(reply, key);
    connect(reply, &QNetworkReply::finished,
            this, &ReactiveObject::onCommandReplyFinished);

    auto* t = new QTimer(this);
    t->setSingleShot(true);
    t->setInterval(kEchoTimeoutMs);
    connect(t, &QTimer::timeout, this, [this, key]() {
        if (!m_inFlight.contains(key)) return;
        rollbackOptimistic(key);
        emit commandTimedOut(QString::fromUtf8(key));
    });
    t->start();
    m_echoTimers.insert(key, t);
}

void ReactiveObject::rollbackOptimistic(const QByteArray& key)
{
    auto it = m_inFlight.find(key);
    if (it == m_inFlight.end()) return;
    InFlight in = it.value();
    m_inFlight.erase(it);
    if (auto* t = m_echoTimers.take(key)) t->deleteLater();

    for (auto bit = in.backup.constBegin(); bit != in.backup.constEnd(); ++bit) {
        m_data->insert(bit.key(), bit.value());
    }
    for (const QString& k : in.addedKeys) {
        m_data->clear(k);
    }
    if (m_inFlight.isEmpty()) setPending(false);
}

void ReactiveObject::onCommandReplyFinished()
{
    auto* reply = qobject_cast<QNetworkReply*>(sender());
    if (!reply) return;
    const QByteArray key = m_replyToKey.take(reply);
    reply->deleteLater();

    const int status = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
    if (reply->error() == QNetworkReply::NoError && status >= 200 && status < 300) {
        // Wait for Mercure echo to clear pending (server's view of truth).
        return;
    }

    QJsonParseError err{};
    const QJsonDocument doc = QJsonDocument::fromJson(reply->readAll(), &err);
    QVariant problem;
    if (err.error == QJsonParseError::NoError && doc.isObject()) {
        problem = doc.object().toVariantMap();
    }
    rollbackOptimistic(key);
    emit commandFailed(QString::fromUtf8(key), status, problem);
}

QByteArray ReactiveObject::buildIdempotencyKey() const
{
    auto* gen = QRandomGenerator::system();
    quint64 a = gen->generate64();
    quint64 b = gen->generate64();
    a = (a & 0xFFFFFFFFFFFF0FFFULL) | 0x0000000000004000ULL;
    b = (b & 0x3FFFFFFFFFFFFFFFULL) | 0x8000000000000000ULL;
    return QString::asprintf(
        "%08llx-%04llx-%04llx-%04llx-%012llx",
        (unsigned long long) ((a >> 32) & 0xFFFFFFFFULL),
        (unsigned long long) ((a >> 16) & 0xFFFFULL),
        (unsigned long long) (a & 0xFFFFULL),
        (unsigned long long) ((b >> 48) & 0xFFFFULL),
        (unsigned long long) (b & 0xFFFFFFFFFFFFULL)
    ).toLatin1();
}

} // namespace PhpQml::Bridge