rublon-ssh/PAM/ssh/include/rublon/core_handler.hpp

#pragma once

#include <rublon/configuration.hpp>
#include <rublon/core_handler_interface.hpp>
#include <rublon/curl.hpp>
#include <rublon/json.hpp>
#include <rublon/pam_action.hpp>
#include <rublon/sign.hpp>
#include <rublon/utils.hpp>
#include <rublon/websockets.hpp>

#include <string_view>
#include <tl/expected.hpp>

namespace rublon {

template < typename HttpHandler = CURL >
class CoreHandler : public CoreHandlerInterface< CoreHandler< HttpHandler > > {
    Configuration _config;
    mutable std::unique_ptr< WebSocket > _ws;

    void signRequest(Request & request) const {
        request.headers["X-Rublon-Signature"] =
          std::pmr::string{signData(request.body, _config.secretKey).c_str(), request.headers.get_allocator()};
    }

    bool hasSignature(const Response & response) const {
        if(not response.headers.count("x-rublon-signature")) {
            log(LogLevel::Error, "No x-rublon-signature");
            return false;
        }
        return true;
    }

    // bool hasRateLimit(const Response & response)const {
    //     if(not response.headers.count("x-ratelimit-remaining")) {
    //         log(LogLevel::Error, "No x-ratelimit-remaining");
    //         return false;
    //     }
    //     return true;
    // }

    // bool rateIsAcceptable(const Response &response)const{
    //// todo validate rate type and number
    // }

    bool signatureIsNatValid(const Response & response) const {
        const auto & xRubResp     = response.headers.at("x-rublon-signature");
        const auto & sign         = signData(response.body, _config.secretKey);
        const bool signatureMatch = xRubResp == sign.data();
        if(not signatureMatch)
            log(LogLevel::Error, "Signature mismatch %s != %s ", xRubResp.c_str(), sign.data());
        return not signatureMatch;
    }

    bool hasException(const Document & coreResponse) const {
        using namespace std::string_view_literals;
        return coreResponse.HasMember("status") and coreResponse["status"].GetString() == "ERROR"sv;
    }

    bool isUnHealthy(const Document & coreResponse) const {
        return coreResponse.HasParseError();
    }

  protected:
    HttpHandler http{};

  public:
    CoreHandler() = delete;
    CoreHandler(const Configuration & config) : _config{config}, http{} {}
    
    tl::expected< std::reference_wrapper< const Response >, Error > validateSignature(const Response & response) const {
        if(hasSignature(response) and signatureIsNatValid(response)) {
            log(LogLevel::Error, "rublon core response is not signed properly");
            return tl::unexpected{CoreHandlerError{CoreHandlerError::BadSigature}};
        }

        return response;
    }

    // tl::expected< std::reference_wrapper< const Response >, Error > validateRate(const Response & response) const {
    //     if(hasSignature(response) and signatureIsNatValid(response)) {
    //         log(LogLevel::Error, "rublon core response is not signed properly");
    //         return tl::unexpected{CoreHandlerError{CoreHandlerError::BadSigature}};
    //     }
    //     return response;
    // }

    tl::expected< Document, Error > validateResponse(RapidJSONPMRAlloc & alloc, const Response & response) const {
        tl::expected< Document, Error > resp{&alloc};
        resp->Parse(response.body.c_str());

        log(LogLevel::Debug, "Begin, Core Response validation");

        if(isUnHealthy(*resp)) {
            log(LogLevel::Error, "Rublon Core responded with broken data");
            return tl::unexpected{CoreHandlerError{CoreHandlerError::BrokenData}};
        } else if(hasException(*resp)) {
            const auto * exception = JSONPointer{"/result/exception", &alloc}.Get(*resp);
            log(LogLevel::Error, "Rublon Core responded with '%s' exception", exception->GetString());
            return handleCoreException(exception->GetString());
        } else if(not hasSignature(response)) {
            // additional check for mallformed responses (A invalid response, without any x-rublon-signature will stop at this check)
            return tl::unexpected{CoreHandlerError{CoreHandlerError::BadSigature}};
        }

        return resp;
    }

    tl::unexpected< Error > handleCoreException(std::string_view exceptionString) const {
        // can happen only dyring check application step
        if(auto error = RublonCheckApplicationException::fromString(exceptionString); error.has_value())
            return tl::unexpected{Error{error.value()}};

        // auth problems likely bad configuration in rublon admin console
        if(auto error = RublonAuthenticationInterrupt::fromString(exceptionString); error.has_value())
            return tl::unexpected{Error{error.value()}};

        // verification error wrong passcode etc.
        if(auto error = WerificationError::fromString(exceptionString); error.has_value())
            return tl::unexpected{Error{error.value()}};

        // other exceptions, just "throw"
        return tl::unexpected{
          Error{CoreHandlerError{CoreHandlerError::RublonCoreException, std::string{exceptionString.data(), exceptionString.size()}}}};
    }

    tl::expected< Document, Error > handleError(const Error & error) const {
        return tl::unexpected{Error{error}};
    }

    tl::expected< Document, Error > request(RapidJSONPMRAlloc & mr, std::string_view path, const Document & body) const {
        memory::StrictMonotonic_8k_HeapResource memoryResource;

        const auto validateSignature = [&](const auto & arg) { return this->validateSignature(arg); };
        const auto validateResponse  = [&](const auto & arg) { return this->validateResponse(mr, arg); };
        const auto handleError       = [&](const auto & error) { return this->handleError(error); };
        const auto pmrs              = [&](const auto & txt) { return std::pmr::string{txt, &memoryResource}; };

        Request request{&memoryResource};
        Response response{&memoryResource};

        request.headers["Content-Type"] = pmrs("application/json");
        request.headers["Accept"]       = pmrs("application/json");

        stringifyTo(body, request.body);
        
        signRequest(request);
        std::pmr::string uri{&memoryResource};
        uri += _config.apiServer.c_str();
        uri += path.data();

        return http
          .request(uri, request, response) //
          .and_then(validateSignature)
          .and_then(validateResponse)
          .or_else(handleError);
    }

    bool createWSConnection(std::string_view tid) const {
        if(not _ws) {
            _ws = std::make_unique< WebSocket >();
        }

        return _ws->AttachToCore(_config.apiServer, tid);
    }

    auto listen() const {
        return _ws->listen();
    }
};

} // namespace rublon