#include "Common.h"
#include "Paths.h"

#include <vector>

static std::wstring ProgramDataDir()
{
    wchar_t buf[MAX_PATH]{};

    DWORD n = GetEnvironmentVariableW(L"ProgramData", buf, _countof(buf));

    if (n > 0 && n < _countof(buf))
        return buf;

    return L"C:\\ProgramData";
}

static std::wstring MachineGuid()
{
    HKEY key = nullptr;
    std::wstring out;

    if (RegOpenKeyExW(
        HKEY_LOCAL_MACHINE,
        L"SOFTWARE\\Microsoft\\Cryptography",
        0,
        KEY_READ | KEY_WOW64_64KEY,
        &key) == ERROR_SUCCESS)
    {
        wchar_t buf[128]{};
        DWORD size = sizeof(buf);
        DWORD type = 0;

        if (RegQueryValueExW(key, L"MachineGuid", nullptr, &type, (LPBYTE)buf, &size) == ERROR_SUCCESS &&
            type == REG_SZ)
        {
            out = buf;
        }

        RegCloseKey(key);
    }

    if (out.empty())
    {
        // Fall back to the volume serial so the path is still per-machine.
        DWORD serial = 0;

        if (!GetVolumeInformationW(L"C:\\", nullptr, 0, &serial, nullptr, nullptr, nullptr, 0))
            serial = 0x12345678;

        wchar_t hex[16]{};
        swprintf_s(hex, L"%08lx", serial);
        out = hex;
    }

    return out;
}

// FNV-1a over the machine GUID: 8 hex chars, stable on this host only.
static std::wstring MachineTag()
{
    const std::wstring guid = MachineGuid();

    unsigned int hash = 2166136261u;

    for (wchar_t c : guid)
    {
        hash ^= (unsigned int)(c & 0xFF);
        hash *= 16777619u;
        hash ^= (unsigned int)((c >> 8) & 0xFF);
        hash *= 16777619u;
    }

    wchar_t out[16]{};
    swprintf_s(out, L"%08x", hash);

    return out;
}

static std::wstring LocalAppDataDir()
{
    wchar_t buf[MAX_PATH]{};

    DWORD n = GetEnvironmentVariableW(L"LOCALAPPDATA", buf, _countof(buf));

    if (n > 0 && n < _countof(buf))
        return buf;

    return ProgramDataDir();
}

static bool RunningElevatedOrSystem()
{
    HANDLE token = nullptr;

    if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &token))
        return false;

    TOKEN_ELEVATION elevation{};
    DWORD len = sizeof(elevation);
    bool elevated = false;

    if (GetTokenInformation(token, TokenElevation, &elevation, len, &len))
        elevated = elevation.TokenIsElevated != 0;

    if (!elevated)
    {
        // SYSTEM is never "elevated" in the UAC sense but is fully privileged.
        DWORD needed = 0;
        GetTokenInformation(token, TokenUser, nullptr, 0, &needed);

        if (needed > 0)
        {
            std::vector<BYTE> buf(needed);
            PTOKEN_USER tu = reinterpret_cast<PTOKEN_USER>(buf.data());

            if (GetTokenInformation(token, TokenUser, tu, needed, &needed))
            {
                LPWSTR sid = nullptr;

                if (ConvertSidToStringSidW(tu->User.Sid, &sid))
                {
                    elevated = wcscmp(sid, L"S-1-5-18") == 0;
                    LocalFree(sid);
                }
            }
        }
    }

    CloseHandle(token);
    return elevated;
}

std::wstring ArdrvRoot()
{
    wchar_t override[MAX_PATH]{};

    DWORD n = GetEnvironmentVariableW(L"ARDRV_ROOT", override, _countof(override));

    if (n > 0 && n < _countof(override))
    {
        std::wstring root = override;
        EnsureDirExists(root);
        return root;
    }

    const std::wstring tag = MachineTag();
    const bool elevated = RunningElevatedOrSystem();

    // Machine-wide deep path for services and elevated runs.
    std::wstring machine = ProgramDataDir() + L"\\Microsoft\\Windows\\Caches\\" + tag;

    // Per-user deep path for an agent running as the interactive user.
    std::wstring user = LocalAppDataDir() + L"\\Microsoft\\Windows\\INetCache\\" + tag;

    std::wstring preferred = elevated ? machine : user;
    std::wstring alternate = elevated ? user : machine;

    EnsureDirExists(preferred);

    if (GetFileAttributesW(preferred.c_str()) != INVALID_FILE_ATTRIBUTES)
        return preferred;

    EnsureDirExists(alternate);

    if (GetFileAttributesW(alternate.c_str()) != INVALID_FILE_ATTRIBUTES)
        return alternate;

    std::wstring flat = ProgramDataDir() + L"\\ArDrvLoader";
    EnsureDirExists(flat);

    return flat;
}

void EnsureDirExists(const std::wstring& path)
{
    if (path.empty())
        return;

    std::wstring partial;

    for (size_t i = 0; i < path.size(); ++i)
    {
        partial += path[i];

        if (path[i] == L'\\' || i + 1 == path.size())
        {
            if (partial.size() > 3)
                CreateDirectoryW(partial.c_str(), nullptr);
        }
    }
}

std::wstring ArdrvServiceDir(const std::wstring& serviceName)
{
    std::wstring dir = ArdrvRoot();
    dir += L"\\";
    dir += serviceName;

    EnsureDirExists(dir);
    return dir;
}

std::wstring ArdrvStageDir()
{
    std::wstring dir = ArdrvRoot();
    dir += L"\\stage";

    EnsureDirExists(dir);
    return dir;
}

std::wstring ArdrvStatePath()
{
    std::wstring path = ArdrvRoot();
    path += L"\\state.dat";

    return path;
}

std::wstring ArdrvLegacyStageDir()
{
    return ProgramDataDir() + L"\\ArDrvLoader\\payloads";
}

std::wstring ArdrvLegacyStatePath()
{
    return ProgramDataDir() + L"\\ArDrvLoader\\host.track";
}