#include "module_proxy.h"
#include "logos_provider_interface.h"
#include "token_manager.h"
#include "logos_rpc_status.h"
#include <QDebug>
#include <QByteArray>
#include <QJsonObject>
#include <QJsonValue>
#include <algorithm>

ModuleProxy::ModuleProxy(LogosProviderObject* provider, QObject* parent)
    : QObject(parent)
    , m_provider(provider)
{
    if (m_provider) {
        m_provider->setEventListener([this](const QString& eventName, const QVariantList& data) {
            qDebug() << "[LogosProviderObject] ModuleProxy: forwarding event" << eventName << "as Qt signal";
            // Events may be fired from any thread (e.g. a module's worker/FFI
            // thread), but this object is the QtRemoteObjects source and must be
            // driven from its own thread. Emitting directly from a foreign
            // thread runs QtRO's source serialization there, racing the source
            // socket against a reply being sent from the source thread, which
            // can silently drop the reply.
            //
            // We *always* queue the emission to this object's own thread, never
            // emit inline — even for a same-thread caller. A module that emits an
            // event from inside an async-call-completion callback (e.g. a
            // gather/fan-out completion firing `balances_updated` from within the
            // `__logos_call_complete__` reply dispatch) is on the source thread,
            // so an AutoConnection would run QtRO's source serialization for the
            // event *re-entrantly*, while a reply is still being marshalled on the
            // same stack — corrupting the source and crashing (SIGSEGV). A queued
            // connection defers the emit to the next event-loop turn, after the
            // reply has been sent, so events and replies stay serialized on the
            // thread QtRO owns. Passing `this` as the context also cancels a
            // queued emission if this object is destroyed first.
            QMetaObject::invokeMethod(this, [this, eventName, data]() {
                emit eventResponse(eventName, data);
            }, Qt::QueuedConnection);
        });
        qDebug() << "[LogosProviderObject] ModuleProxy: created, wrapping LogosProviderObject"
                 << m_provider->providerName();
    }
}

ModuleProxy::~ModuleProxy()
{
    qDebug() << "ModuleProxy: destroyed";
}

bool ModuleProxy::saveToken(const QString& from_module_name, const QString& token)
{
    if (from_module_name.isEmpty()) {
        qWarning() << "ModuleProxy: Cannot save token with empty module name";
        return false;
    }
    if (token.isEmpty()) {
        qWarning() << "ModuleProxy: Cannot save empty token for module:" << from_module_name;
        return false;
    }

    m_tokens[from_module_name] = token;
    qDebug() << "ModuleProxy: Token saved for module:" << from_module_name;
    return true;
}

void ModuleProxy::setTokenValidator(TokenValidator validator)
{
    m_validator = std::move(validator);
}

// QtRO / local path: RemoteTransportHost only ever serves a local socket, so
// the wire is "local". Forwards to the transport-aware overload.
QVariant ModuleProxy::callRemoteMethod(const QString& authToken, const QString& methodName, const QVariantList& args)
{
    return callRemoteMethod(authToken, methodName, args, QStringLiteral("local"));
}

QVariant ModuleProxy::callRemoteMethod(const QString& authToken, const QString& methodName, const QVariantList& args, const QString& transportProtocol)
{
    if (!m_provider) {
        qWarning() << "ModuleProxy: Cannot call method on null provider:" << methodName;
        return QVariant();
    }

    if (methodName.isEmpty()) {
        qWarning() << "ModuleProxy: Method name cannot be empty";
        return QVariant();
    }

    if (methodName == "getPluginMethods" && args.isEmpty()) {
        return QVariant(getPluginMethods());
    }

    if (methodName == "getPluginEvents" && args.isEmpty()) {
        return QVariant(getPluginEvents());
    }

    if (methodName == "getPluginInterface" && args.isEmpty()) {
        return QVariant(getPluginInterface());
    }
    // NOTE: the three getPlugin* introspection calls above intentionally stay
    // ungated. They expose only the method/event signatures (no business logic
    // or state) and are needed before any token exists — a caller discovers a
    // module's interface as part of the connection handshake, ahead of the
    // capability_module token exchange. Everything past this point is a real
    // business-method dispatch and MUST be authorized.

    if (!isAuthorized(authToken, transportProtocol)) {
        qWarning() << "ModuleProxy: rejecting unauthorized call to" << methodName
                   << "- auth token not recognized";
        // Structured rejection instead of a bare QVariant() so a NEW consumer can
        // drop its stale token and re-exchange (see logos_rpc_status.h /
        // LogosAPIClient::invokeRemoteMethod). OLD consumers convert this to the
        // same empty/default they already got from QVariant(), so it's backward
        // compatible.
        return logos::makeUnauthorizedSentinel();
    }

    // SECURITY: never log call arguments — they routinely carry secrets
    // (mnemonics, passwords, tokens, key material). Log only the method name and
    // the argument count, matching the other transport call sites.
    qDebug() << "ModuleProxy: callRemoteMethod" << methodName << "args:" << args.size();
    const QVariant result = m_provider->callMethod(methodName, args);

    // Module identity, for a provider whose own dispatch does not answer it.
    //
    // A module built through the LIDL frontend has name()/version() generated
    // into its dispatch, so it never reaches here. A legacy module derives no
    // contract and has neither — yet every provider already knows both, via the
    // providerName()/providerVersion() vtable slots the interface has always
    // had. Answering from those makes identity uniform across every module in
    // the fleet without touching a single one of them.
    //
    // Placed AFTER dispatch, deliberately: an invalid QVariant is this slot's
    // "unknown method" answer, so a provider that DOES implement name() keeps
    // its own result and nothing existing changes behaviour. Gated on an empty
    // argument list so a same-named method taking arguments is untouched.
    if (!result.isValid() && args.isEmpty()) {
        if (methodName == QLatin1String("name"))
            return QVariant(m_provider->providerName());
        if (methodName == QLatin1String("version"))
            return QVariant(m_provider->providerVersion());
    }
    return result;
}

namespace {
// note: this is to ensure comparison is constant time to prevent timing attacks
// Length-independent constant-time comparison of two tokens. Returns true only
// when both byte sequences are identical. We compare over the longer of the two
// lengths (folding any length difference into the result) so the running time
// does not reveal a correct prefix or the secret's length.
bool constantTimeEquals(const QString& a, const QString& b)
{
    const QByteArray ba = a.toUtf8();
    const QByteArray bb = b.toUtf8();
    const int n = std::max(ba.size(), bb.size());
    // A different length is a mismatch, but keep scanning to stay constant-time.
    int diff = ba.size() ^ bb.size();
    for (int i = 0; i < n; ++i) {
        const unsigned char ca = i < ba.size() ? static_cast<unsigned char>(ba[i]) : 0;
        const unsigned char cb = i < bb.size() ? static_cast<unsigned char>(bb[i]) : 0;
        diff |= (ca ^ cb);
    }
    return diff == 0;
}
} // namespace

bool ModuleProxy::informModuleToken(const QString& authToken, const QString& moduleName, const QString& token)
{
    if (!m_provider) {
        qWarning() << "ModuleProxy: Cannot inform token on null provider";
        return false;
    }

    const QString coreToken = TokenManager::instance().getToken(QStringLiteral("core"));
    const QString capToken  = TokenManager::instance().getToken(QStringLiteral("capability_module"));
    const bool callerIsTrusted =
        (!coreToken.isEmpty() && constantTimeEquals(authToken, coreToken)) ||
        (!capToken.isEmpty()  && constantTimeEquals(authToken, capToken));
    if (authToken.isEmpty() || !callerIsTrusted) {
        qWarning() << "ModuleProxy: rejecting informModuleToken for" << moduleName
                   << "- caller is not the trusted core/capability_module channel";
        return false;
    }

    if (moduleName.isEmpty()) {
        qWarning() << "ModuleProxy: Cannot inform token with empty module name";
        return false;
    }
    if (token.isEmpty()) {
        qWarning() << "ModuleProxy: Cannot inform empty token for module:" << moduleName;
        return false;
    }

    return m_provider->informModuleToken(moduleName, token);
}

bool ModuleProxy::isAuthorized(const QString& authToken, const QString& transportProtocol) const
{
    // Fail closed: an empty token is never valid, even if some empty value
    // somehow ended up in a token store.
    if (authToken.isEmpty()) {
        return false;
    }

    // A token is valid only if THIS module actually issued it to some caller.
    // Two stores hold issued tokens:
    //   * m_tokens          — legacy per-proxy store (LogosAPIProvider::saveToken)
    //   * TokenManager      — the capability-flow store that informModuleToken
    //                         writes when capability_module mints a token for a
    //                         (caller, target) pair.
    // We scan every issued token with a constant-time compare and never early
    // out, so neither a match position nor the number of issued tokens leaks
    // through timing.
    bool authorized = false;
    for (auto it = m_tokens.constBegin(); it != m_tokens.constEnd(); ++it) {
        authorized |= constantTimeEquals(authToken, it.value());
    }
    for (const QString& key : TokenManager::instance().getTokenKeys()) {
        authorized |= constantTimeEquals(authToken, TokenManager::instance().getToken(key));
    }
    if (authorized) {
        return true;
    }

    // Not one of our own issued tokens — give a host-installed validator the
    // chance to accept it for this transport. This is how operator-issued named
    // tokens (validated against the daemon's TokenStore, with expiry and
    // local_only enforced by `transportProtocol`) authorize a call without
    // being pre-registered in the in-process stores above.
    if (m_validator) {
        return m_validator(authToken, transportProtocol);
    }
    return false;
}

namespace {
// getMethods() returns the module's full interface — both methods and events,
// each tagged with a "type" ("method"/"event"). Split it back out. An entry
// with no "type" counts as a method, so modules built against the pre-events
// SDK (whose getMethods() contains no events) report zero events, not a crash.
QJsonArray filterInterface(const QJsonArray& interface, bool keepEvents)
{
    QJsonArray out;
    for (const QJsonValue& v : interface) {
        const bool isEvent =
            v.toObject().value(QStringLiteral("type")).toString() == QStringLiteral("event");
        if (isEvent == keepEvents) out.append(v);
    }
    return out;
}
} // namespace

QJsonArray ModuleProxy::getPluginInterface()
{
    if (!m_provider) return QJsonArray();

    qDebug() << "[LogosProviderObject] ModuleProxy: calling LogosProviderObject::getMethods()";
    QJsonArray iface = m_provider->getMethods();

    // Advertise module identity for a provider that does not list it itself.
    //
    // The dispatch fallback in callRemoteMethod answers name()/version() for
    // every module; without this, a legacy module would ANSWER them while `lm`
    // and every untyped caller reported it had no such method — present to
    // whoever already knew to ask, invisible to everyone else. The two have to
    // agree, so they are derived from the same providerName()/providerVersion().
    //
    // Additive only: an entry the provider already lists wins, so a module with
    // a generated (or hand-written) name() keeps its own description, signature
    // and parameters.
    auto lists = [&iface](QLatin1String name) {
        for (const QJsonValue& v : iface)
            if (v.isObject() && v.toObject().value("name").toString() == name)
                return true;
        return false;
    };
    // Signatures only -- this listing describes the interface, it does not
    // carry values. The VALUES come from the same two provider accessors in
    // callRemoteMethod, which is what keeps the listing and the answer in step.
    const struct { QLatin1String name; const char* desc; } identity[] = {
        { QLatin1String("name"),    "The module's name, as declared in its metadata." },
        { QLatin1String("version"), "The module's version, as declared in its metadata." },
    };
    for (const auto& id : identity) {
        if (lists(id.name)) continue;
        QJsonObject entry;
        entry["name"] = QString(id.name);
        entry["type"] = QStringLiteral("method");
        entry["signature"] = QString(id.name) + QStringLiteral("()");
        entry["returnType"] = QStringLiteral("QString");
        entry["isInvokable"] = true;
        entry["description"] = QString::fromLatin1(id.desc);
        iface.append(entry);
    }
    return iface;
}

QJsonArray ModuleProxy::getPluginMethods()
{
    return filterInterface(getPluginInterface(), /*keepEvents=*/false);
}

QJsonArray ModuleProxy::getPluginEvents()
{
    return filterInterface(getPluginInterface(), /*keepEvents=*/true);
}

#include "moc_module_proxy.cpp"

// ── ModuleHandshakeProxy ─────────────────────────────────────────────────────

ModuleHandshakeProxy::ModuleHandshakeProxy(ModuleProxy* proxy, QObject* parent)
    : QObject(parent)
    , m_proxy(proxy)
{
}

bool ModuleHandshakeProxy::informModuleToken(const QString& authToken,
                                             const QString& moduleName,
                                             const QString& token)
{
    if (!m_proxy) {
        qWarning() << "ModuleHandshakeProxy: no module proxy to deliver the token for"
                   << moduleName;
        return false;
    }
    // Same authorization and same store as the business object — this is only a
    // different door onto it, reachable earlier.
    return m_proxy->informModuleToken(authToken, moduleName, token);
}