#include "TicketHelper.h"
#include <QCoreApplication>
#include <QDateTime>
#include <QDir>
#include <QFile>
#include <QJsonDocument>
#include <QJsonObject>
#include <QMessageAuthenticationCode>
#include <QSaveFile>
#include <QStandardPaths>
#include <QUuid>

static QByteArray ticketMac(const QJsonObject& payload, const QString& secret)
{
    return QMessageAuthenticationCode::hash(
        QJsonDocument(payload).toJson(QJsonDocument::Compact), secret.toUtf8(), QCryptographicHash::Sha256).toHex();
}

bool TicketHelper::createTicket(const QString& appId, const QString& deviceId,
                                const QString& version, const QString& secret,
                                QString* ticketPath, QString* errorMessage)
{
    if (appId.isEmpty() || version.isEmpty() || secret.isEmpty()) {
        if (errorMessage) *errorMessage = "ticket identity or secret is empty";
        return false;
    }
    const QDateTime now = QDateTime::currentDateTimeUtc();
    QJsonObject payload{
        {"app_id", appId}, {"device_id", deviceId}, {"version", version},
        {"nonce", QUuid::createUuid().toString(QUuid::WithoutBraces)},
        {"issued_at", now.toString(Qt::ISODate)},
        {"expires_at", now.addSecs(60).toString(Qt::ISODate)},
        {"signature_alg", "HMAC-SHA256"}
    };
    QJsonObject wrapper{{"payload", payload}, {"signature", QString::fromLatin1(ticketMac(payload, secret))}};
    const QString dirPath = QDir(QStandardPaths::writableLocation(QStandardPaths::TempLocation)).filePath("marsco_tickets");
    if (!QDir().mkpath(dirPath)) { if (errorMessage) *errorMessage = "cannot create ticket directory"; return false; }
    const QString path = QDir(dirPath).filePath("ticket_" + QUuid::createUuid().toString(QUuid::WithoutBraces) + ".json");
    QSaveFile file(path);
    const QByteArray bytes = QJsonDocument(wrapper).toJson(QJsonDocument::Compact);
    if (!file.open(QIODevice::WriteOnly) || file.write(bytes) != bytes.size() || !file.commit()) {
        if (errorMessage) *errorMessage = "cannot save ticket";
        return false;
    }
    QFile::setPermissions(path, QFileDevice::ReadOwner | QFileDevice::WriteOwner);
    if (ticketPath) *ticketPath = path;
    return true;
}

bool TicketHelper::consumeAndVerify(const QString& ticketPath, const QString& expectedAppId,
                                    const QString& expectedDeviceId, const QString& expectedVersion,
                                    const QString& secret, QString* errorMessage)
{
    const QString consumingPath = ticketPath + ".consuming."
        + QString::number(QCoreApplication::applicationPid());
    if (!QFile::rename(ticketPath, consumingPath)) {
        if (errorMessage) *errorMessage = "ticket missing or already consumed";
        return false;
    }
    QFile file(consumingPath);
    if (!file.open(QIODevice::ReadOnly)) {
        QFile::remove(consumingPath);
        if (errorMessage) *errorMessage = "cannot read claimed ticket";
        return false;
    }
    const QByteArray raw = file.readAll(); file.close();
    QFile::remove(consumingPath); // Consume once; it must not be replayed regardless of success or failure.
    QJsonParseError parseError;
    const QJsonDocument doc = QJsonDocument::fromJson(raw, &parseError);
    if (parseError.error != QJsonParseError::NoError || !doc.isObject()) {
        if (errorMessage) *errorMessage = "invalid ticket JSON"; return false;
    }
    const QJsonObject wrapper = doc.object();
    const QJsonObject payload = wrapper.value("payload").toObject();
    const QByteArray actual = wrapper.value("signature").toString().toLatin1();
    const QByteArray expected = ticketMac(payload, secret);
    const QDateTime issued = QDateTime::fromString(payload.value("issued_at").toString(), Qt::ISODate);
    const QDateTime expires = QDateTime::fromString(payload.value("expires_at").toString(), Qt::ISODate);
    const QDateTime now = QDateTime::currentDateTimeUtc();
    const bool identityOk = payload.value("app_id").toString() == expectedAppId
        && payload.value("device_id").toString() == expectedDeviceId
        && payload.value("version").toString() == expectedVersion;
    const bool timeOk = issued.isValid() && expires.isValid() && issued <= now.addSecs(5)
        && expires >= now && issued.secsTo(expires) <= 65;
    if (actual.isEmpty() || actual != expected || !identityOk || !timeOk
        || payload.value("nonce").toString().isEmpty()) {
        if (errorMessage) *errorMessage = "ticket signature, identity, time or nonce invalid";
        return false;
    }
    return true;
}