/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#define WIN32_LEAN_AND_MEAN
#include <windows.h>

#include <cstring>
#include <wchar.h>

#include <comphelper/windowsStart.hxx>

// Needed for CreateEnvironmentBlock
#include <userenv.h>
#pragma comment(lib, "userenv.lib")

/**
 * Get the length that the string will take and takes into account the
 * additional length if the string needs to be quoted and if characters need to
 * be escaped.
 */
static int ArgStrLen(const wchar_t *s)
{
    int i = wcslen(s);
    bool hasDoubleQuote = wcschr(s, L'"') != nullptr;
    // Only add doublequotes if the string contains a space or a tab
    bool addDoubleQuotes = wcspbrk(s, L" \t") != nullptr;

    if (addDoubleQuotes)
    {
        i += 2; // initial and final doublequote
    }

    if (hasDoubleQuote)
    {
        int backslashes = 0;
        while (*s)
        {
            if (*s == '\\')
            {
                ++backslashes;
            }
            else
            {
                if (*s == '"')
                {
                    // Escape the doublequote and all backslashes preceding the doublequote
                    i += backslashes + 1;
                }

                backslashes = 0;
            }

            ++s;
        }
    }

    return i;
}

/**
 * Copy string "s" to string "d", quoting the argument as appropriate and
 * escaping doublequotes along with any backslashes that immediately precede
 * doublequotes.
 * The CRT parses this to retrieve the original argc/argv that we meant,
 * see STDARGV.C in the MSVC CRT sources.
 *
 * @return the end of the string
 */
static wchar_t* ArgToString(wchar_t *d, const wchar_t *s)
{
    bool hasDoubleQuote = wcschr(s, L'"') != nullptr;
    // Only add doublequotes if the string contains a space or a tab
    bool addDoubleQuotes = wcspbrk(s, L" \t") != nullptr;

    if (addDoubleQuotes)
    {
        *d = '"'; // initial doublequote
        ++d;
    }

    if (hasDoubleQuote)
    {
        int backslashes = 0;
        while (*s)
        {
            if (*s == '\\')
            {
                ++backslashes;
            }
            else
            {
                if (*s == '"')
                {
                    // Escape the doublequote and all backslashes preceding the doublequote
                    for (int i = 0; i <= backslashes; ++i)
                    {
                        *d = '\\';
                        ++d;
                    }
                }

                backslashes = 0;
            }

            *d = *s;
            ++d;
            ++s;
        }
    }
    else
    {
        wcscpy(d, s);
        d += wcslen(s);
    }

    if (addDoubleQuotes)
    {
        *d = '"'; // final doublequote
        ++d;
    }

    return d;
}

/**
 * Creates a command line from a list of arguments. The returned
 * string is allocated with "malloc" and should be "free"d.
 *
 * argv is UTF8
 */
wchar_t*
MakeCommandLine(int argc, wchar_t **argv)
{
    int i;
    int len = 0;

    // The + 1 of the last argument handles the allocation for null termination
    for (i = 0; i < argc && argv[i]; ++i)
        len += ArgStrLen(argv[i]) + 1;

    // Protect against callers that pass 0 arguments
    if (len == 0)
        len = 1;

    wchar_t *s = static_cast<wchar_t*>(malloc(len * sizeof(wchar_t)));
    if (!s)
        return nullptr;

    wchar_t *c = s;
    for (i = 0; i < argc && argv[i]; ++i)
    {
        c = ArgToString(c, argv[i]);
        if (i + 1 != argc)
        {
            *c = ' ';
            ++c;
        }
    }

    *c = '\0';

    return s;
}

BOOL
WinLaunchChild(const wchar_t *exePath,
               int argc,
               wchar_t **argv,
               HANDLE userToken,
               HANDLE *hProcess)
{
    wchar_t *cl;
    bool ok;

    cl = MakeCommandLine(argc, argv);
    if (!cl)
    {
        return FALSE;
    }

    STARTUPINFOW si;
    std::memset(&si, 0, sizeof si);
    si.cb = sizeof(STARTUPINFOW);
    si.lpDesktop = const_cast<LPWSTR>(L"winsta0\\Default");
    PROCESS_INFORMATION pi;
    std::memset(&pi, 0, sizeof pi);

    if (userToken == nullptr)
    {
        ok = CreateProcessW(exePath,
                            cl,
                            nullptr,  // no special security attributes
                            nullptr,  // no special thread attributes
                            FALSE, // don't inherit filehandles
                            0,     // creation flags
                            nullptr,  // inherit my environment
                            nullptr,  // use my current directory
                            &si,
                            &pi);
    }
    else
    {
        // Create an environment block for the process we're about to start using
        // the user's token.
        LPVOID environmentBlock = nullptr;
        if (!CreateEnvironmentBlock(&environmentBlock, userToken, TRUE))
        {
            environmentBlock = nullptr;
        }

        ok = CreateProcessAsUserW(userToken,
                                  exePath,
                                  cl,
                                  nullptr,  // no special security attributes
                                  nullptr,  // no special thread attributes
                                  FALSE,    // don't inherit filehandles
                                  0,        // creation flags
                                  environmentBlock,
                                  nullptr,  // use my current directory
                                  &si,
                                  &pi);

        if (environmentBlock)
        {
            DestroyEnvironmentBlock(environmentBlock);
        }
    }

    if (ok)
    {
        if (hProcess)
        {
            *hProcess = pi.hProcess; // the caller now owns the HANDLE
        }
        else
        {
            CloseHandle(pi.hProcess);
        }
        CloseHandle(pi.hThread);
    }
    else
    {
        LPVOID lpMsgBuf = nullptr;
        FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                       FORMAT_MESSAGE_FROM_SYSTEM |
                       FORMAT_MESSAGE_IGNORE_INSERTS,
                       nullptr,
                       GetLastError(),
                       MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                       reinterpret_cast<LPWSTR>(&lpMsgBuf),
                       0,
                       nullptr);
        wprintf(L"Error restarting: %s\n", lpMsgBuf ? lpMsgBuf : L"(null)");
        if (lpMsgBuf)
            HeapFree(GetProcessHeap(), 0, lpMsgBuf);
    }

    free(cl);

    return ok;
}