//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2022 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

#pragma once

#include <memory>
#include <sstream>
#include <vector>

#include <openvpn/buffer/asiobuf.hpp>
#include <openvpn/common/exception.hpp>
#include <openvpn/common/size.hpp>
#include <openvpn/common/to_string.hpp>
#include <openvpn/time/time.hpp>
#include <openvpn/transport/client/transbase.hpp>
#include <openvpn/transport/dco.hpp>
#include <openvpn/tun/tunmtu.hpp>
#include <openvpn/tun/builder/capture.hpp>
#include <openvpn/tun/client/tunbase.hpp>

#if !defined(ENABLE_OVPNDCOWIN)
#include <openvpn/tun/linux/client/tunmethods.hpp>
#endif

#if defined(ENABLE_KOVPN)
#include <openvpn/kovpn/kodevtun.hpp>
#include <openvpn/kovpn/kostats.hpp>
#include <openvpn/kovpn/kovpn.hpp>
#include <openvpn/kovpn/rps_xps.hpp>
#elif defined(ENABLE_OVPNDCO)
#include <openvpn/buffer/buffer.hpp>
#include <openvpn/common/uniqueptr.hpp>
#include <openvpn/dco/key.hpp>
#include <openvpn/tun/linux/client/genl.hpp>
#include <openvpn/tun/linux/client/sitnl.hpp>
#elif defined(ENABLE_OVPNDCOWIN)
#include <bcrypt.h>
#include <openvpn/dco/key.hpp>
#include <openvpn/dco/ovpn-dco.h>
#include <openvpn/win/modname.hpp>
#else
#error either ENABLE_KOVPN, ENABLE_OVPNDCO or ENABLE_OVPNDCOWIN must be defined
#endif

#include <openvpn/dco/korekey.hpp>

// client-side DCO (Data Channel Offload) module for Linux/kovpn

namespace openvpn::DCOTransport {
enum
{
    OVPN_PEER_ID_UNDEF = 0x00FFFFFF,
};

class ClientConfig : public DCO,
                     public TransportClientFactory,
                     public TunClientFactory
{
  public:
    typedef RCPtr<ClientConfig> Ptr;

    std::string dev_name;

    DCO::TransportConfig transport;
    DCO::TunConfig tun;

    unsigned int ping_restart_override = 0;

    void process_push(const OptionList &opt) override
    {
        transport.remote_list->process_push(opt);
    }

    void finalize(const bool disconnected) override
    {
#if defined(ENABLE_OVPNDCOWIN)
        if (disconnected)
            tun.tun_persist.reset();
#endif
    }

    TunClientFactory::Ptr new_tun_factory(const DCO::TunConfig &conf, const OptionList &opt) override
    {
        tun = conf;

        // set a default MTU
        if (!tun.tun_prop.mtu)
            tun.tun_prop.mtu = TUN_MTU_DEFAULT;

        // parse "dev" option
        {
            const Option *dev = opt.get_ptr("dev");
            if (dev)
                dev_name = dev->get(1, 64);
            else
                dev_name = "ovpnc";
        }

        // parse ping-restart-override
        ping_restart_override = opt.get_num<decltype(ping_restart_override)>(
            "ping-restart-override", 1, ping_restart_override, 0, 3600);

        return TunClientFactory::Ptr(this);
    }

    TransportClientFactory::Ptr new_transport_factory(const DCO::TransportConfig &conf) override
    {
        transport = conf;
        return TransportClientFactory::Ptr(this);
    }

    TunClient::Ptr new_tun_client_obj(openvpn_io::io_context &io_context,
                                      TunClientParent &parent,
                                      TransportClient *transcli) override;

    TransportClient::Ptr new_transport_client_obj(openvpn_io::io_context &io_context,
                                                  TransportClientParent *parent) override;

    static DCO::Ptr new_controller(TunBuilderBase *tb)
    {
        auto ctrl = new ClientConfig();
        if (ctrl)
            ctrl->builder = tb;
        return ctrl;
    }

    bool supports_proto_v3() override
    {
        /* Currently, there is no version of ovpn-dco for Linux or Windows that supports
         * the new features, so we always return false here */
        return false;
    }

  protected:
    ClientConfig() = default;
};

class Client : public TransportClient,
               public TunClient,
               public AsyncResolvableUDP
{
    friend class ClientConfig;

    typedef RCPtr<Client> Ptr;

  public:
    // transport methods

    bool transport_send_queue_empty() override
    {
        return false;
    }

    bool transport_has_send_queue() override
    {
        return false;
    }

    size_t transport_send_queue_size() override
    {
        return 0;
    }

    void reset_align_adjust(const size_t align_adjust) override
    {
    }

    void transport_stop_requeueing() override
    {
    }

    void server_endpoint_info(std::string &host,
                              std::string &port,
                              std::string &proto,
                              std::string &ip_addr) const override
    {
        host = server_host;
        port = server_port;
        const IP::Addr addr = server_endpoint_addr();
        proto = std::string(transport_protocol().str());
        proto += "-DCO";
        ip_addr = addr.to_string();
    }

    void stop() override
    {
        stop_();
    }

    // tun methods

    void set_disconnect() override
    {
    }

    bool tun_send(BufferAllocated &buf) override // return true if send succeeded
    {
        return false;
    }

    std::string vpn_ip4() const override
    {
        if (state->vpn_ip4_addr.specified())
            return state->vpn_ip4_addr.to_string();
        else
            return "";
    }

    std::string vpn_ip6() const override
    {
        if (state->vpn_ip6_addr.specified())
            return state->vpn_ip6_addr.to_string();
        else
            return "";
    }

    std::string vpn_gw4() const override
    {
        if (state->vpn_ip4_gw.specified())
            return state->vpn_ip4_gw.to_string();
        else
            return "";
    }

    std::string vpn_gw6() const override
    {
        if (state->vpn_ip6_gw.specified())
            return state->vpn_ip6_gw.to_string();
        else
            return "";
    }

    int vpn_mtu() const override
    {
        return state->mtu;
    }

  protected:
    Client(openvpn_io::io_context &io_context_arg,
           ClientConfig *config_arg,
           TransportClientParent *parent_arg)
        : AsyncResolvableUDP(io_context_arg), io_context(io_context_arg),
          halt(false), state(new TunProp::State()), config(config_arg),
          transport_parent(parent_arg), tun_parent(nullptr),
          peer_id(OVPN_PEER_ID_UNDEF)
    {
    }

    void transport_reparent(TransportClientParent *parent_arg) override
    {
        transport_parent = parent_arg;
    }

    virtual void stop_() = 0;

    openvpn_io::io_context &io_context;
    bool halt;

    TunProp::State::Ptr state;

    ClientConfig::Ptr config;
    TransportClientParent *transport_parent;
    TunClientParent *tun_parent;

    ActionList::Ptr remove_cmds;

    std::string server_host;
    std::string server_port;

    uint32_t peer_id;
};

#if defined(ENABLE_KOVPN)
#include <openvpn/kovpn/kovpncli.hpp>
inline DCO::Ptr new_controller(TunBuilderBase *)
{
    return KovpnClientConfig::new_controller();
}
inline TransportClient::Ptr
ClientConfig::new_transport_client_obj(openvpn_io::io_context &io_context,
                                       TransportClientParent *parent)
{
    return TransportClient::Ptr(new KovpnClient(io_context, this, parent));
}
#elif defined(ENABLE_OVPNDCO)
#include <openvpn/dco/ovpndcocli.hpp>
inline DCO::Ptr new_controller(TunBuilderBase *tb)
{
    if (!OvpnDcoClient::available(tb))
        return nullptr;

    CryptoAlgs::allow_dc_algs({CryptoAlgs::CHACHA20_POLY1305,
                               CryptoAlgs::AES_128_GCM,
                               CryptoAlgs::AES_192_GCM,
                               CryptoAlgs::AES_256_GCM});
    return ClientConfig::new_controller(tb);
}
inline TransportClient::Ptr
ClientConfig::new_transport_client_obj(openvpn_io::io_context &io_context,
                                       TransportClientParent *parent)
{
    return TransportClient::Ptr(new OvpnDcoClient(io_context, this, parent));
}
#elif defined(ENABLE_OVPNDCOWIN)
#include <openvpn/dco/ovpndcowincli.hpp>
inline DCO::Ptr new_controller(TunBuilderBase *tb)
{
    if (!OvpnDcoWinClient::available())
        return nullptr;

    std::list<CryptoAlgs::Type> algs{CryptoAlgs::AES_128_GCM, CryptoAlgs::AES_192_GCM, CryptoAlgs::AES_256_GCM};
    BCRYPT_ALG_HANDLE h;
    NTSTATUS status = BCryptOpenAlgorithmProvider(&h, L"CHACHA20_POLY1305", NULL, 0);
    if (BCRYPT_SUCCESS(status))
    {
        BCryptCloseAlgorithmProvider(h, 0);
        algs.push_back(CryptoAlgs::CHACHA20_POLY1305);
    }

    CryptoAlgs::allow_dc_algs(algs);
    return ClientConfig::new_controller(nullptr);
}
inline TransportClient::Ptr
ClientConfig::new_transport_client_obj(openvpn_io::io_context &io_context,
                                       TransportClientParent *parent)
{
    return TransportClient::Ptr(new OvpnDcoWinClient(io_context, this, parent));
}
#endif

inline TunClient::Ptr
ClientConfig::new_tun_client_obj(openvpn_io::io_context &io_context,
                                 TunClientParent &parent,
                                 TransportClient *transcli)
{
    Client *cli = static_cast<Client *>(transcli);
    cli->tun_parent = &parent;
    return TunClient::Ptr(cli);
}
} // namespace openvpn::DCOTransport