// tun_windows.c - Wintun implementation
#include "../lib/debug_config.h"
#include "../lib/u_async.h"
#include "tun_if.h"
#include "wintun.h"
#include "ll_queue.h"          // ← добавлено
#include "etcp.h"              // ← добавлено (struct ETCP_FRAGMENT)
#include <windows.h>
#include <iphlpapi.h>
#include <ws2tcpip.h>
#include <stdio.h>

// Wintun function pointers
static HMODULE wintun_dll = NULL;
static WINTUN_CREATE_ADAPTER_FUNC          *WintunCreateAdapter = NULL;
static WINTUN_CLOSE_ADAPTER_FUNC           *WintunCloseAdapter = NULL;
static WINTUN_OPEN_ADAPTER_FUNC            *WintunOpenAdapter = NULL;
static WINTUN_GET_ADAPTER_LUID_FUNC        *WintunGetAdapterLUID = NULL;
static WINTUN_START_SESSION_FUNC           *WintunStartSession = NULL;
static WINTUN_END_SESSION_FUNC             *WintunEndSession = NULL;
static WINTUN_GET_READ_WAIT_EVENT_FUNC     *WintunGetReadWaitEvent = NULL;
static WINTUN_RECEIVE_PACKET_FUNC          *WintunReceivePacket = NULL;
static WINTUN_RELEASE_RECEIVE_PACKET_FUNC  *WintunReleaseReceivePacket = NULL;
static WINTUN_ALLOCATE_SEND_PACKET_FUNC    *WintunAllocateSendPacket = NULL;
static WINTUN_SEND_PACKET_FUNC             *WintunSendPacket = NULL;

static int wintun_load_dll(void)
{
    if (wintun_dll) return 0;

    wchar_t path[MAX_PATH];
    if (GetModuleFileNameW(NULL, path, MAX_PATH)) {
        for (int i = (int)wcslen(path)-1; i >= 0; i--) {
            if (path[i] == L'\\' || path[i] == L'/') {
                path[i+1] = L'\0';
                wcscat(path, L"wintun.dll");
                wintun_dll = LoadLibraryW(path);
                break;
            }
        }
    }
    if (!wintun_dll) wintun_dll = LoadLibraryA("wintun.dll");

    if (!wintun_dll) {
        DEBUG_ERROR(DEBUG_CATEGORY_TUN, "wintun.dll not found");
        return -1;
    }

    WintunCreateAdapter         = (WINTUN_CREATE_ADAPTER_FUNC*)GetProcAddress(wintun_dll, "WintunCreateAdapter");
    WintunCloseAdapter          = (WINTUN_CLOSE_ADAPTER_FUNC*)GetProcAddress(wintun_dll, "WintunCloseAdapter");
    WintunOpenAdapter           = (WINTUN_OPEN_ADAPTER_FUNC*)GetProcAddress(wintun_dll, "WintunOpenAdapter");
    WintunGetAdapterLUID        = (WINTUN_GET_ADAPTER_LUID_FUNC*)GetProcAddress(wintun_dll, "WintunGetAdapterLUID");
    WintunStartSession          = (WINTUN_START_SESSION_FUNC*)GetProcAddress(wintun_dll, "WintunStartSession");
    WintunEndSession            = (WINTUN_END_SESSION_FUNC*)GetProcAddress(wintun_dll, "WintunEndSession");
    WintunGetReadWaitEvent      = (WINTUN_GET_READ_WAIT_EVENT_FUNC*)GetProcAddress(wintun_dll, "WintunGetReadWaitEvent");
    WintunReceivePacket         = (WINTUN_RECEIVE_PACKET_FUNC*)GetProcAddress(wintun_dll, "WintunReceivePacket");
    WintunReleaseReceivePacket  = (WINTUN_RELEASE_RECEIVE_PACKET_FUNC*)GetProcAddress(wintun_dll, "WintunReleaseReceivePacket");
    WintunAllocateSendPacket    = (WINTUN_ALLOCATE_SEND_PACKET_FUNC*)GetProcAddress(wintun_dll, "WintunAllocateSendPacket");
    WintunSendPacket            = (WINTUN_SEND_PACKET_FUNC*)GetProcAddress(wintun_dll, "WintunSendPacket");

    if (!WintunCreateAdapter || !WintunCloseAdapter || !WintunOpenAdapter ||
        !WintunGetAdapterLUID || !WintunStartSession || !WintunEndSession ||
        !WintunGetReadWaitEvent || !WintunReceivePacket || !WintunReleaseReceivePacket ||
        !WintunAllocateSendPacket || !WintunSendPacket) {
        DEBUG_ERROR(DEBUG_CATEGORY_TUN, "Failed to resolve Wintun functions");
        FreeLibrary(wintun_dll);
        wintun_dll = NULL;
        return -1;
    }
    return 0;
}

// ===================================================================
// Helper: set IP + MTU + bring interface up
// ===================================================================
static int wintun_configure_interface(WINTUN_ADAPTER_HANDLE adapter, const char* ip_str, int mtu)
{
    NET_LUID luid;
    WintunGetAdapterLUID(adapter, &luid);

    char ip_only[64] = {0};
    int prefix = 32;
    if (ip_str) {
        strncpy(ip_only, ip_str, sizeof(ip_only)-1);
        char* slash = strchr(ip_only, '/');
        if (slash) {
            *slash = '\0';
            prefix = atoi(slash + 1);
            if (prefix < 0 || prefix > 32) prefix = 32;
        }
    }

    struct in_addr addr;
    if (inet_pton(AF_INET, ip_only, &addr) != 1) {
        DEBUG_ERROR(DEBUG_CATEGORY_TUN, "Invalid IP: %s", ip_str);
        return -1;
    }

    // IP address
    MIB_UNICASTIPADDRESS_ROW row = {0};
    InitializeUnicastIpAddressEntry(&row);
    row.Address.si_family = AF_INET;
    row.Address.Ipv4.sin_family = AF_INET;
    row.Address.Ipv4.sin_addr.s_addr = addr.s_addr;
    row.InterfaceLuid = luid;
    row.OnLinkPrefixLength = (UINT8)prefix;
    row.DadState = IpDadStatePreferred;
    row.SuffixOrigin = IpSuffixOriginManual;
    row.PrefixOrigin = IpPrefixOriginManual;

    DWORD err = CreateUnicastIpAddressEntry(&row);
    if (err != NO_ERROR && err != ERROR_OBJECT_ALREADY_EXISTS) {
        DEBUG_ERROR(DEBUG_CATEGORY_TUN, "CreateUnicastIpAddressEntry failed: %lu", err);
        return -1;
    }

    // MTU
    if (mtu > 0) {
        MIB_IPINTERFACE_ROW ifRow = {0};
        InitializeIpInterfaceEntry(&ifRow);
        ifRow.Family = AF_INET;
        ifRow.InterfaceLuid = luid;
        if (GetIpInterfaceEntry(&ifRow) == NO_ERROR) {
            ifRow.NlMtu = mtu;
            SetIpInterfaceEntry(&ifRow);
        }
    }

    // Bring UP
    NET_IFINDEX idx = 0;
    if (ConvertInterfaceLuidToIndex(&luid, &idx) == NO_ERROR) {
        MIB_IFROW ifr = {0};
        ifr.dwIndex = idx;
        if (GetIfEntry(&ifr) == NO_ERROR) {
            ifr.dwAdminStatus = MIB_IF_ADMIN_STATUS_UP;
            SetIfEntry(&ifr);
        }
    }
    return 0;
}

// ===================================================================
// Platform functions
// ===================================================================
int tun_platform_init(struct tun_if* tun, const char* ifname, const char* ip_str, int mtu)
{
    if (wintun_load_dll() != 0) return -1;

    wchar_t wname[128] = L"utun";
    if (ifname && ifname[0])
        MultiByteToWideChar(CP_UTF8, 0, ifname, -1, wname, 128);

    WINTUN_ADAPTER_HANDLE adapter = WintunCreateAdapter(wname, L"utun", NULL);
    if (!adapter) {
        DEBUG_ERROR(DEBUG_CATEGORY_TUN, "WintunCreateAdapter failed: %lu", GetLastError());
        return -1;
    }

    WINTUN_SESSION_HANDLE session = WintunStartSession(adapter, 0x400000); // 4 MiB ring
    if (!session) {
        DEBUG_ERROR(DEBUG_CATEGORY_TUN, "WintunStartSession failed: %lu", GetLastError());
        WintunCloseAdapter(adapter);
        return -1;
    }

    if (wintun_configure_interface(adapter, ip_str, mtu) != 0) {
        WintunEndSession(session);
        WintunCloseAdapter(adapter);
        return -1;
    }

    tun->platform_handle = session;
    tun->adapter_handle  = adapter;
    strncpy(tun->ifname, ifname && ifname[0] ? ifname : "utun", sizeof(tun->ifname)-1);
    return 0;
}

void tun_platform_cleanup(struct tun_if* tun)
{
    if (tun->platform_handle) {
        WintunEndSession((WINTUN_SESSION_HANDLE)tun->platform_handle);
        tun->platform_handle = NULL;
    }
    if (tun->adapter_handle) {
        WintunCloseAdapter((WINTUN_ADAPTER_HANDLE)tun->adapter_handle);
        tun->adapter_handle = NULL;
    }
}

ssize_t tun_platform_read(struct tun_if* tun, uint8_t* buf, size_t len)
{
    if (!tun->platform_handle) return -1;
    DWORD size;
    BYTE* pkt = WintunReceivePacket((WINTUN_SESSION_HANDLE)tun->platform_handle, &size);
    if (!pkt) {
        if (GetLastError() == ERROR_NO_MORE_ITEMS) return 0;
        return -1;
    }
    if (size > len) size = (DWORD)len;
    memcpy(buf, pkt, size);
    WintunReleaseReceivePacket((WINTUN_SESSION_HANDLE)tun->platform_handle, pkt);
    return (ssize_t)size;
}

ssize_t tun_platform_write(struct tun_if* tun, const uint8_t* buf, size_t len)
{
    if (!tun->platform_handle) return -1;
    BYTE* pkt = WintunAllocateSendPacket((WINTUN_SESSION_HANDLE)tun->platform_handle, (DWORD)len);
    if (!pkt) return -1;
    memcpy(pkt, buf, len);
    WintunSendPacket((WINTUN_SESSION_HANDLE)tun->platform_handle, pkt);
    return (ssize_t)len;
}

int tun_platform_get_poll_fd(struct tun_if* tun)
{
    (void)tun;
    return -1;
}

// ===================================================================
// Windows-only notify
// ===================================================================
static void tun_output_notify(void* arg)
{
    struct tun_if* tun = (struct tun_if*)arg;
    if (tun) {
        DEBUG_DEBUG(DEBUG_CATEGORY_TUN, "TUN read notify → output_queue (%s)", tun->ifname);
    }
}

// ===================================================================
// Read thread
// ===================================================================
DWORD WINAPI tun_read_thread_proc(LPVOID arg)
{
    struct tun_if* tun = (struct tun_if*)arg;
    HANDLE event = WintunGetReadWaitEvent((WINTUN_SESSION_HANDLE)tun->platform_handle);
    if (!event) return 1;

    HANDLE handles[2] = {event, tun->stop_event};

    while (tun->running) {
        if (WaitForMultipleObjects(2, handles, FALSE, INFINITE) != WAIT_OBJECT_0)
            break;

        uint8_t buf[TUN_MAX_PACKET_SIZE];
        int got_packet = 0;

        ssize_t n;
        while ((n = tun_platform_read(tun, buf, sizeof(buf))) > 0) {
            got_packet = 1;

            uint8_t* data = malloc(n);
            if (!data) { tun->read_errors++; continue; }
            memcpy(data, buf, n);

            struct ETCP_FRAGMENT* pkt = (struct ETCP_FRAGMENT*)queue_entry_new_from_pool(tun->pool);
            if (!pkt) {
                free(data);
                tun->read_errors++;
                continue;
            }

            pkt->ll.dgram = data;
            pkt->ll.len = n;

            EnterCriticalSection(&tun->output_queue_lock);
            int ok = queue_data_put(tun->output_queue, (struct ll_entry*)pkt, 0);
            LeaveCriticalSection(&tun->output_queue_lock);

            if (ok != 0) {
                free(data);
                memory_pool_free(tun->pool, pkt);
                tun->read_errors++;
            } else {
                tun->bytes_read += n;
                tun->packets_read++;
            }
        }

        if (got_packet) {
            uasync_post(tun->ua, tun_output_notify, tun);
        }
    }
    return 0;
}