#include "PolicyHelper.h"
#include "ConfigHelper.h"
#include <QApplication>
#include <QDateTime>
#include <QDir>
#include <QFile>
#include <QJsonArray>
#include <QJsonDocument>
#include <algorithm>
#ifdef HAVE_OPENSSL
#include <openssl/evp.h>
#include <openssl/pem.h>
#endif

PolicyHelper::PolicyHelper(const QString& baseDir) : m_baseDir(baseDir) {}

static QString resolvePolicyPath(const QString& baseDir, const QString& relativePath, bool forWrite)
{
    const QString defaultPolicy = QStringLiteral("config/version_policy.dat");
    if (relativePath == defaultPolicy) {
        const QString runtimePolicy = ConfigHelper::instance().policyPath();
        if (forWrite || QFile::exists(runtimePolicy))
            return runtimePolicy;
    }
    if (QDir::isAbsolutePath(relativePath))
        return relativePath;
    return baseDir + "/" + relativePath;
}

bool PolicyHelper::loadPolicy(const QString& relativePath)
{
    QFile file(resolvePolicyPath(m_baseDir, relativePath, false));
    if (!file.open(QIODevice::ReadOnly)) { m_error = "Cannot open policy file"; return false; }
    QJsonParseError error;
    const QJsonDocument doc = QJsonDocument::fromJson(file.readAll(), &error);
    if (error.error != QJsonParseError::NoError || !doc.isObject()) {
        m_error = "Invalid policy JSON: " + error.errorString(); return false;
    }
    return loadPolicyObject(doc.object());
}

bool PolicyHelper::loadPolicyObject(const QJsonObject& policy, const QString& signedText)
{
    m_policy = policy; m_signedText = signedText; m_loaded = true; m_error.clear();
    return isValid();
}

bool PolicyHelper::savePolicy(const QString& relativePath) const
{
    const QByteArray bytes = QJsonDocument(m_policy).toJson(QJsonDocument::Indented);
    QString writeError;
    const QString path = resolvePolicyPath(m_baseDir, relativePath, true);
    if (!ConfigHelper::writeFileWithElevationIfNeeded(path, bytes, &writeError)) {
        m_error = "Cannot save policy file: " + writeError;
        return false;
    }
    m_error.clear();
    return true;
}

QByteArray PolicyHelper::canonicalPolicyBytes(const QJsonObject& policy) const
{
    QJsonObject copy = policy; copy.remove("signature");
    auto sortObject = [&](auto&& self, const QJsonObject& obj) -> QJsonObject {
        QStringList keys = obj.keys(); std::sort(keys.begin(), keys.end());
        QJsonObject sorted;
        for (const QString& key : keys) {
            QJsonValue value = obj.value(key);
            if (value.isObject()) value = self(self, value.toObject());
            else if (value.isArray()) {
                QJsonArray array;
                for (QJsonValue item : value.toArray()) {
                    if (item.isObject()) item = self(self, item.toObject());
                    array.append(item);
                }
                value = array;
            }
            sorted.insert(key, value);
        }
        return sorted;
    };
    return QJsonDocument(sortObject(sortObject, copy)).toJson(QJsonDocument::Compact);
}

bool PolicyHelper::verifySignature(const QByteArray& payload, const QString& signatureBase64) const
{
#ifndef HAVE_OPENSSL
    Q_UNUSED(payload); Q_UNUSED(signatureBase64); m_error = "OpenSSL unavailable"; return false;
#else
    QString keyPath = m_baseDir + "/config/manifest_public_key.pem";
    QFile keyFile(keyPath);
    if (!keyFile.open(QIODevice::ReadOnly)) { m_error = "Cannot open policy public key"; return false; }
    const QByteArray keyData = keyFile.readAll();
    BIO* bio = BIO_new_mem_buf(keyData.constData(), keyData.size());
    EVP_PKEY* key = bio ? PEM_read_bio_PUBKEY(bio, nullptr, nullptr, nullptr) : nullptr;
    if (bio) BIO_free(bio);
    if (!key) { m_error = "Invalid policy public key"; return false; }
    EVP_MD_CTX* ctx = EVP_MD_CTX_new();
    const QByteArray signature = QByteArray::fromBase64(signatureBase64.toUtf8());
    bool ok = ctx && EVP_DigestVerifyInit(ctx, nullptr, EVP_sha256(), nullptr, key) == 1
        && EVP_DigestVerifyUpdate(ctx, payload.constData(), payload.size()) == 1
        && EVP_DigestVerifyFinal(ctx, reinterpret_cast<const unsigned char*>(signature.constData()), signature.size()) == 1;
    if (ctx) EVP_MD_CTX_free(ctx); EVP_PKEY_free(key);
    if (!ok) m_error = "Invalid RSA policy signature";
    return ok;
#endif
}

bool PolicyHelper::isValid() const
{
    if (!m_loaded) return false;
    const QStringList required{"app_id","channel","current_version","policy_seq","allow_run",
        "force_update","allow_rollback","offline_allowed","valid_until","signature_alg","key_id","signature"};
    for (const QString& key : required) if (!m_policy.contains(key)) { m_error = "Missing policy field: " + key; return false; }
    if (m_policy.value("signature_alg").toString() != "RSA-2048-SHA256") return false;
    const QByteArray payload = m_signedText.isEmpty() ? canonicalPolicyBytes(m_policy) : m_signedText.toUtf8();
    return verifySignature(payload, m_policy.value("signature").toString());
}
QString PolicyHelper::errorString() const { return m_error; }
bool PolicyHelper::isVersionAllowed(const QString& version) const {
    if (!isValid()) return false;
    for (const QJsonValue& v : m_policy.value("disabled_versions").toArray()) if (v.toString() == version) return false;
    return true;
}
bool PolicyHelper::allowRun() const { return isValid() && m_policy.value("allow_run").toBool(); }
bool PolicyHelper::forceUpdate() const { return isValid() && m_policy.value("force_update").toBool(); }
bool PolicyHelper::allowRollback() const { return isValid() && m_policy.value("allow_rollback").toBool(); }
bool PolicyHelper::isOfflineAllowed() const { return isValid() && m_policy.value("offline_allowed").toBool(); }
bool PolicyHelper::gitTagsEnabled() const { return isValid() && m_policy.value("git_tags_enabled").toBool(); }
bool PolicyHelper::isExpired() const {
    if (!isValid()) return true;
    const QDateTime expiry = QDateTime::fromString(m_policy.value("valid_until").toString(), Qt::ISODate);
    return !expiry.isValid() || QDateTime::currentDateTimeUtc() > expiry;
}
qint64 PolicyHelper::policySeq() const { return isValid() ? m_policy.value("policy_seq").toVariant().toLongLong() : 0; }
QString PolicyHelper::message() const { return m_policy.value("message").toString(); }