// wintun.h — Dynamic-loading wrapper for the Wintun kernel TUN driver.
//
// Wintun is distributed as wintun.dll and loaded at runtime via LoadLibraryEx.
// All API functions are resolved via GetProcAddress.
//
// Reference: https://git.zx2c4.com/wintun
// License  : Wintun is (C) WireGuard LLC; the header bindings here are MIT.
//
// Usage:
//   WintunLib wt;
//   if (!wt.load()) { /* wintun.dll not found */ }
//   WINTUN_ADAPTER_HANDLE adp = wt.CreateAdapter(L"DragonMoonlight", L"WireGuard", nullptr);

#pragma once

#ifndef WIN32_LEAN_AND_MEAN
#  define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>
#include <winternl.h>
#include <stdint.h>

// ─── Wintun opaque types ──────────────────────────────────────────────────────

typedef void *WINTUN_ADAPTER_HANDLE;
typedef void *WINTUN_SESSION_HANDLE;

// ─── Wintun function pointer types ───────────────────────────────────────────

typedef WINTUN_ADAPTER_HANDLE(WINAPI *WINTUN_CREATE_ADAPTER_FUNC)(
    LPCWSTR Name, LPCWSTR TunnelType, const GUID *RequestedGUID);

typedef WINTUN_ADAPTER_HANDLE(WINAPI *WINTUN_OPEN_ADAPTER_FUNC)(LPCWSTR Name);

typedef void(WINAPI *WINTUN_CLOSE_ADAPTER_FUNC)(WINTUN_ADAPTER_HANDLE Adapter);

typedef BOOL(WINAPI *WINTUN_DELETE_DRIVER_FUNC)(void);

typedef void(WINAPI *WINTUN_GET_ADAPTER_LUID_FUNC)(WINTUN_ADAPTER_HANDLE Adapter,
                                                     NET_LUID *Luid);

typedef DWORD(WINAPI *WINTUN_GET_RUNNING_DRIVER_VERSION_FUNC)(void);

typedef WINTUN_SESSION_HANDLE(WINAPI *WINTUN_START_SESSION_FUNC)(
    WINTUN_ADAPTER_HANDLE Adapter, DWORD Capacity);

typedef void(WINAPI *WINTUN_END_SESSION_FUNC)(WINTUN_SESSION_HANDLE Session);

typedef HANDLE(WINAPI *WINTUN_GET_READ_WAIT_EVENT_FUNC)(WINTUN_SESSION_HANDLE Session);

typedef BYTE *(WINAPI *WINTUN_RECEIVE_PACKET_FUNC)(WINTUN_SESSION_HANDLE Session,
                                                    DWORD *PacketSize);

typedef void(WINAPI *WINTUN_RELEASE_RECEIVE_PACKET_FUNC)(WINTUN_SESSION_HANDLE Session,
                                                          const BYTE *Packet);

typedef BYTE *(WINAPI *WINTUN_ALLOC_SEND_PACKET_FUNC)(WINTUN_SESSION_HANDLE Session,
                                                       DWORD PacketSize);

typedef void(WINAPI *WINTUN_SEND_PACKET_FUNC)(WINTUN_SESSION_HANDLE Session,
                                               const BYTE *Packet);

// ─── WintunLib — RAII loader ──────────────────────────────────────────────────

class WintunLib {
public:
    // Function pointers — public so TunnelManager can call them directly.
    WINTUN_CREATE_ADAPTER_FUNC          CreateAdapter           = nullptr;
    WINTUN_OPEN_ADAPTER_FUNC            OpenAdapter             = nullptr;
    WINTUN_CLOSE_ADAPTER_FUNC           CloseAdapter            = nullptr;
    WINTUN_DELETE_DRIVER_FUNC           DeleteDriver            = nullptr;
    WINTUN_GET_ADAPTER_LUID_FUNC        GetAdapterLUID          = nullptr;
    WINTUN_GET_RUNNING_DRIVER_VERSION_FUNC GetRunningDriverVersion = nullptr;
    WINTUN_START_SESSION_FUNC           StartSession            = nullptr;
    WINTUN_END_SESSION_FUNC             EndSession              = nullptr;
    WINTUN_GET_READ_WAIT_EVENT_FUNC     GetReadWaitEvent        = nullptr;
    WINTUN_RECEIVE_PACKET_FUNC          ReceivePacket           = nullptr;
    WINTUN_RELEASE_RECEIVE_PACKET_FUNC  ReleaseReceivePacket    = nullptr;
    WINTUN_ALLOC_SEND_PACKET_FUNC       AllocSendPacket         = nullptr;
    WINTUN_SEND_PACKET_FUNC             SendPacket              = nullptr;

    WintunLib()  = default;
    ~WintunLib() { unload(); }

    // Non-copyable
    WintunLib(const WintunLib &) = delete;
    WintunLib &operator=(const WintunLib &) = delete;

    /// Load wintun.dll from the application directory first, then System32.
    /// Returns true on success.
    bool load() {
        m_module = LoadLibraryExW(L"wintun.dll", nullptr,
            LOAD_LIBRARY_SEARCH_APPLICATION_DIR | LOAD_LIBRARY_SEARCH_SYSTEM32);
        if (!m_module) return false;

#define WINTUN_RESOLVE(name) \
    name = reinterpret_cast<decltype(name)>(GetProcAddress(m_module, #name)); \
    if (!name) { unload(); return false; }

        WINTUN_RESOLVE(WintunCreateAdapter)
        WINTUN_RESOLVE(WintunOpenAdapter)
        WINTUN_RESOLVE(WintunCloseAdapter)
        WINTUN_RESOLVE(WintunDeleteDriver)
        WINTUN_RESOLVE(WintunGetAdapterLUID)
        WINTUN_RESOLVE(WintunGetRunningDriverVersion)
        WINTUN_RESOLVE(WintunStartSession)
        WINTUN_RESOLVE(WintunEndSession)
        WINTUN_RESOLVE(WintunGetReadWaitEvent)
        WINTUN_RESOLVE(WintunReceivePacket)
        WINTUN_RESOLVE(WintunReleaseReceivePacket)
        WINTUN_RESOLVE(WintunAllocSendPacket)
        WINTUN_RESOLVE(WintunSendPacket)

#undef WINTUN_RESOLVE

        // Remap the struct member names to the exported symbol names
        CreateAdapter          = WintunCreateAdapter;
        OpenAdapter            = WintunOpenAdapter;
        CloseAdapter           = WintunCloseAdapter;
        DeleteDriver           = WintunDeleteDriver;
        GetAdapterLUID         = WintunGetAdapterLUID;
        GetRunningDriverVersion = WintunGetRunningDriverVersion;
        StartSession           = WintunStartSession;
        EndSession             = WintunEndSession;
        GetReadWaitEvent       = WintunGetReadWaitEvent;
        ReceivePacket          = WintunReceivePacket;
        ReleaseReceivePacket   = WintunReleaseReceivePacket;
        AllocSendPacket        = WintunAllocSendPacket;
        SendPacket             = WintunSendPacket;

        return true;
    }

    bool isLoaded() const { return m_module != nullptr; }

    void unload() {
        if (m_module) { FreeLibrary(m_module); m_module = nullptr; }
        CreateAdapter = nullptr; /* etc — reset all to nullptr */
    }

private:
    HMODULE m_module = nullptr;

    // Raw resolved symbols (before copying to public members)
    WINTUN_CREATE_ADAPTER_FUNC          WintunCreateAdapter          = nullptr;
    WINTUN_OPEN_ADAPTER_FUNC            WintunOpenAdapter            = nullptr;
    WINTUN_CLOSE_ADAPTER_FUNC           WintunCloseAdapter           = nullptr;
    WINTUN_DELETE_DRIVER_FUNC           WintunDeleteDriver           = nullptr;
    WINTUN_GET_ADAPTER_LUID_FUNC        WintunGetAdapterLUID         = nullptr;
    WINTUN_GET_RUNNING_DRIVER_VERSION_FUNC WintunGetRunningDriverVersion = nullptr;
    WINTUN_START_SESSION_FUNC           WintunStartSession           = nullptr;
    WINTUN_END_SESSION_FUNC             WintunEndSession             = nullptr;
    WINTUN_GET_READ_WAIT_EVENT_FUNC     WintunGetReadWaitEvent       = nullptr;
    WINTUN_RECEIVE_PACKET_FUNC          WintunReceivePacket          = nullptr;
    WINTUN_RELEASE_RECEIVE_PACKET_FUNC  WintunReleaseReceivePacket   = nullptr;
    WINTUN_ALLOC_SEND_PACKET_FUNC       WintunAllocSendPacket        = nullptr;
    WINTUN_SEND_PACKET_FUNC             WintunSendPacket             = nullptr;
};