add a post with a attachment programmatically

hi
i am trying to add a post programmatically , and i used this:

https://wordpress.pastebin.ca/2048284

it adds the post correctly but without the attachment (thumbnail) !
can anyone help me?

Note: i am taking the images from:

$filename=$_FILES[‘file’][‘name’];

after this when i edit the post i find the name of the image is written
but no attachment