#include "MercureClient.h"

#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QTimer>
#include <QUrl>
#include <QUrlQuery>

#include <algorithm>

namespace PhpQml::Bridge {

MercureClient::MercureClient(QObject* parent)
    : QObject(parent)
    , m_nam(new QNetworkAccessManager(this))
{
}

MercureClient::~MercureClient()
{
    teardownReply();
}

void MercureClient::setHubUrl(const QString& url)
{
    if (m_hubUrl == url) return;
    m_hubUrl = url;
    emit hubUrlChanged();
}

void MercureClient::setTopic(const QString& t)
{
    if (m_topic == t) return;
    m_topic = t;
    emit topicChanged();
}

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

void MercureClient::start()
{
    m_userStopped = false;
    m_currentBackoffMs = kInitialBackoffMs;
    if (m_reconnectTimer) m_reconnectTimer->stop();
    doConnect();
}

void MercureClient::stop()
{
    m_userStopped = true;
    if (m_reconnectTimer) m_reconnectTimer->stop();
    teardownReply();
    setActive(false);
}

void MercureClient::doConnect()
{
    if (m_userStopped) return;
    if (m_hubUrl.isEmpty() || m_topic.isEmpty()) return;
    if (m_reply) return;  // already connecting / connected

    QUrl u(m_hubUrl);
    QUrlQuery query(u);
    query.addQueryItem(QStringLiteral("topic"), m_topic);
    u.setQuery(query);

    QNetworkRequest req(u);
    req.setRawHeader("Accept", "text/event-stream");
    req.setRawHeader("Cache-Control", "no-cache");
    if (!m_lastEventId.isEmpty()) {
        req.setRawHeader("Last-Event-ID", m_lastEventId.toUtf8());
    }
    if (!m_token.isEmpty()) {
        req.setRawHeader("Authorization", "Bearer " + m_token.toUtf8());
    }
    // Disable transfer timeout — SSE is a long-lived stream.
    req.setTransferTimeout(0);

    m_reply = m_nam->get(req);
    connect(m_reply, &QNetworkReply::readyRead, this, &MercureClient::onReadyRead);
    connect(m_reply, &QNetworkReply::finished, this, &MercureClient::onFinished);

    setActive(true);
}

void MercureClient::onReadyRead()
{
    if (!m_reply) return;

    while (m_reply->canReadLine()) {
        QByteArray line = m_reply->readLine();
        // Strip trailing line terminator (handles both \n and \r\n).
        while (line.endsWith('\n') || line.endsWith('\r')) {
            line.chop(1);
        }

        if (line.isEmpty()) {
            emitMessage();
            continue;
        }
        if (line.startsWith(':')) continue;  // SSE comment

        const int colon = line.indexOf(':');
        if (colon < 0) continue;  // malformed
        const QByteArray field = line.left(colon);
        QByteArray value = line.mid(colon + 1);
        if (value.startsWith(' ')) value = value.mid(1);

        if (field == "data") {
            m_dataLines << QString::fromUtf8(value);
        } else if (field == "id") {
            m_pendingEventId = value;
        }
        // event:, retry: are intentionally ignored for Phase 1.
    }

    // Successful read — reset backoff so a future drop reconnects fast.
    m_currentBackoffMs = kInitialBackoffMs;
}

void MercureClient::emitMessage()
{
    if (m_dataLines.isEmpty() && m_pendingEventId.isEmpty()) return;

    if (!m_pendingEventId.isEmpty()) {
        const QString id = QString::fromUtf8(m_pendingEventId);
        if (id != m_lastEventId) {
            m_lastEventId = id;
            emit lastEventIdChanged();
        }
    }
    if (!m_dataLines.isEmpty()) {
        emit update(m_dataLines.join(QChar('\n')), QString::fromUtf8(m_pendingEventId));
    }

    m_dataLines.clear();
    m_pendingEventId.clear();
}

void MercureClient::onFinished()
{
    if (!m_reply) return;

    const auto err = m_reply->error();
    const QString errStr = m_reply->errorString();
    teardownReply();
    setActive(false);

    if (m_userStopped) return;

    if (err != QNetworkReply::NoError && err != QNetworkReply::OperationCanceledError) {
        emit error(errStr);
    }

    scheduleReconnect();
}

void MercureClient::scheduleReconnect()
{
    if (m_userStopped) return;
    if (m_hubUrl.isEmpty() || m_topic.isEmpty()) return;

    if (!m_reconnectTimer) {
        m_reconnectTimer = new QTimer(this);
        m_reconnectTimer->setSingleShot(true);
        connect(m_reconnectTimer, &QTimer::timeout, this, &MercureClient::doConnect);
    }
    m_reconnectTimer->start(m_currentBackoffMs);
    m_currentBackoffMs = std::min(m_currentBackoffMs * 2, kMaxBackoffMs);
}

void MercureClient::teardownReply()
{
    if (m_reply) {
        disconnect(m_reply, nullptr, this, nullptr);
        m_reply->abort();
        m_reply->deleteLater();
        m_reply = nullptr;
    }
    m_dataLines.clear();
    m_pendingEventId.clear();
}

void MercureClient::setActive(bool a)
{
    if (m_active == a) return;
    m_active = a;
    emit activeChanged();
}

} // namespace PhpQml::Bridge