# The directory of the ASS files that need to be cleaned
$dir = "C:\Users\Kintoki\Desktop\ASS_files"

$files = Get-ChildItem "$dir" | Where-Object {$_.Extension -eq ".ass"}
#Start batch loop
for ($i=0; $i -lt $files.Count; $i++) {
    $subs = $files[$i].FullName
    $ASS = Get-Content -LiteralPath $subs
    Write-Host ('>> File: ' + $files[$i].BaseName)
    #Remove non-used styles
    foreach($elem in ($ASS -match "Style:\s(\D.*)").Replace("Style: ","")){
        $tmp = $elem.split(",") | Select-Object -Index 0
        if($tmp){
            $str = ',' + $tmp + ','
            [int]$occ = (Select-String -InputObject $ASS -Pattern $str -AllMatches).Matches.Count
            #check if the first assigned actor/name is actually used, else remove
            if($occ -le 0){
                $ASS = $ASS -ne "Style: $elem"
                Write-Host "* Removed stylename '$tmp' because it does not appear in ASS"
            }
        }
    }
    Set-Content -Encoding UTF8 -LiteralPath $subs -Value $ASS
}