::Want to understand how this code works? www.ss64.com/nt has a great explanation for most of the commands in here

::Keep the window clean and easy to read
@echo off

::Set the title of the window
title Garry's Mod Server Installer and Updater v0.1

::I don't know what this means but it fixes random things that weren't working related to the if statements
setlocal enabledelayedexpansion

::If cfg.txt does not exist, prompt the user to input an install directory and then write it to a file (So it only has to be typed once)
::If it does exist, read it and set variable downloadDir to the contents of the file (which would be the install directory)

echo ::=============================================::
echo Welcome to Cheezus' Server Creator and Updater Script
echo If this is your first time using this, follow all of the instructions carefully
echo ::=============================================::

if not exist cfg.txt (
    echo:
    echo Set the install location. Example - C:\My GMod Server\
    echo YOU MUST INCLUDE A FINAL BACKSLASH AT THE END\
    SET /p downloadDir=Install Directory: %"="%
    echo !downloadDir! >cfg.txt
) else (
    SET /p downloadDir=<cfg.txt
    echo Previous install directory automatically detected: !downloadDir!
    echo:
)

::If the download directory folder does not exist, create it
if not exist "%downloadDir%" (
    echo:
    echo Install location does not exist, creating folder...
    echo:
    mkdir "%downloadDir%"
)

::Set the command prompt to run directly from the download directory
cd "%downloadDir%"

::If steamcmd.exe already exists, skip downloading and run it. If not, assume it isn't installed and download it
if exist steamcmd.exe (
    echo:
    echo SteamCMD already installed, starting...
    echo:
    goto run
)

::If steamcmd.exe does not exist, use Windows PowerShell to pull it from Steam's website
echo Downloading SteamCMD...
    powershell -Command "(New-Object Net.WebClient).DownloadFile('https://steamcdn-a.akamaihd.net/client/installer/steamcmd.zip', 'steamcmd.zip')"

::Random script I found online for extracting files.
::It works by using the echo command to write line-by-line to a temporary .vbs script file, and then running it afterwards (see line 76)
echo Extracting...

    echo ZipFile="steamcmd.zip" > zip.vbs
    echo ExtractTo="./" >> zip.vbs

    echo Set fso = CreateObject("Scripting.FileSystemObject") >> zip.vbs
    echo sourceFile = fso.GetAbsolutePathName(ZipFile) >> zip.vbs
    echo destFolder = fso.GetAbsolutePathName(ExtractTo) >> zip.vbs

    echo Set objShell = CreateObject("Shell.Application") >> zip.vbs
    echo Set FilesInZip=objShell.NameSpace(sourceFile).Items() >> zip.vbs
    echo objShell.NameSpace(destFolder).copyHere FilesInZip, 16 >> zip.vbs

    echo Set fso = Nothing >> zip.vbs
    echo Set objShell = Nothing >> zip.vbs
    echo Set FilesInZip = Nothing >> zip.vbs

CScript zip.vbs

::Don't want to keep the downloaded zip and the temporary vbs script lying around do we?
echo Finished extracting, cleaning up...
del steamcmd.zip
del zip.vbs

:run
goto skip
::Launch steamcmd.exe, log in to the Valve servers and begin downloading Garry's Mod Dedicated Server
::Afterwards, it validates the files and then closes itself
steamcmd.exe +login anonymous +app_update 4020 validate +quit
:skip
::After the server downloads, create an instance of SRCDS Guardian to launch it
::Each line of code here is writing itself to a new .bat file which will be used to start the server
echo Garry's Mod Dedicated Server successfully downloaded and validated.
echo:

:choice1
echo If you were just updating, type N. If this is your first time, type Y.
set /P c=Was this your first time running this script?[Y/N]
if /I "%c%" EQU "Y" goto :first
if /I "%c%" EQU "N" goto :notfirst
goto :choice1

:first
echo Let's set up some things like...
echo:
echo The name of your server?
SET /p servername=Server Name: %"="%
echo:
echo The default map?
SET /p map=Default Map: %"="%
echo:
echo Max amount of players?
SET /p maxplayers=Max Players: %"="%
echo:
echo Remote console password?
SET /p rconpassword=RCON Password: %"="%
echo:
echo Workshop collection ID? If you aren't sure, leave this blank
SET /p hostworkshopcollectionid=Workshop Collection ID: %"="%
echo:
echo Workshop auth key? If you don't have a collection for your server, leave this blank
SET /p authkey=Workshop Authentication Key: %"="%
echo:
del %downloadDir%\steamapps\common\GarrysModDS\garrysmod\cfg\server.cfg
echo hostname "%servername%" >%downloadDir%\steamapps\common\GarrysModDS\garrysmod\cfg\server.cfg
:choice2
echo If you don't already have a shortcut for your server, type Y
set /P c=Do you want to create an instance of SRCDS Guardian?[Y/N]?
if /I "%c%" EQU "Y" goto :yesguardian
if /I "%c%" EQU "N" goto :noguardian
goto :choice2

:yesguardian
echo Creating instance of SRCDS Guardian...
echo:
if not exist "%~dp0\Launch GMod Server - SRCDS Guardian 3.bat" (
    cd !%~dp0!

    echo ::File generated by Cheezus' Server Installer:: > "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::  SRCDS Guardian 3.0   :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::         Mooga         :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::       SRCDS.com       :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=========================================================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: Thanks To Black-Sky ^& Drocona for making SRCDS Guardian :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: This script is open source.  Feel free to edit at will. :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::                                                         :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: This script was writen for the use of the srcds.com     :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: online community.  If you are interested in running a   :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: Source Dedicated Server or need help, drop by our       :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: forums at... http://forums.srcds.com                    :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=========================================================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::  SET YOUR VARIABLES!  : class="re0">: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::  Window and Log name  :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::  Replace "My Server"  :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo set servername=%servername% >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::   Your start command  :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::    Replace after =    :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================::
    echo set runcmd=%downloadDir%steamapps\common\GarrysModDS\srcds.exe -console -game garrysmod +map %map% +maxplayers %maxplayers% +rcon_password %rconpassword% +host_workshop_collection %hostworkshopcollectionid% -authkey %authkey% >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::   End of variables    :: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::=======================:: >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: This will keep the window clean and easy to read >> "Launch Server - SRCDS Guardian 3.bat"
    echo @echo off >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: Sets the title of the window >> "Launch Server - SRCDS Guardian 3.bat"
    echo title SRCDS Guardian 3.0   %%servername%% >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: Clears the window incase there is anything there >> "Launch Server - SRCDS Guardian 3.bat"
    echo cls >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: Prints to the window what we are doing >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo SRCDS Guardian 3.0 has been started! >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo. >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo ************************************************************************* >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo To close the server, close this window and type exit in the server window >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo ************************************************************************* >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo. >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo. >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo %%servername%% is now starting... >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo :: This is a return point in case the server crashes or is closed >> "Launch Server - SRCDS Guardian 3.bat"
    echo :restart >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo. >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo ^(%%date%%^)^(%%time%%^) %%servername%% is now ONLINE >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo Watching %%servername%% for crashes... >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::Start the actual server >> "Launch Server - SRCDS Guardian 3.bat"
    echo start /wait %%runcmd%% >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo. >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo ^(%%date%%^)^(%%time%%^) Crash or Close detected! >> "Launch Server - SRCDS Guardian 3.bat"
    echo echo %%servername%% is now restarting... >> "Launch Server - SRCDS Guardian 3.bat"
    echo: >> "Launch Server - SRCDS Guardian 3.bat"
    echo ::Server crashed or closed, so we point it to the return point to start the server again >> "Launch Server - SRCDS Guardian 3.bat"
    echo goto restart >> "Launch Server - SRCDS Guardian 3.bat"
)
echo:
:noguardian
:notfirst
echo Setup finished.
echo If you delete the cfg.txt this script created, you'll have to type the
echo directory again next time you run it.
echo ::==============================::
echo To launch your server, click on the file that was created when this script ran - 'Launch Server - SRCDS Guardian 3.bat'
echo ::==============================::
echo Whenever you want to update your server, run this script and it will automatically update.
:end
pause