Dynamic Bitly url shorten in SMS SFMC

Question

In sms, I want to add the cloud page URL with the dynamic values. When someone click on the URL it redirects to the landing page and data is inserted into the data extension using the lookup function.

What is working, I am able to shorten the dynamic cloud page URL using the bitly API.

Issue: While generating URL shorten using bitly API the data is inserted in the Data extension even when the SMS is previewed. The reason is, while bitly shortening the URL is hit to the cloud page and data is inserted.

Can anyone help with the solution?

<script runat="server" language="ampscript">
   Set @urlToShorten1 = CloudPagesURL(2545, 'identity_identifier', @ii)
    Set @access_token = Lookup("ENT.settings", "bitly_access_token", "selector", "1")
    Set @id_country = "FR"
    Set @group_guid = Lookup("ENT.settings_bitly_guid", "guid", "home_country", @id_country)
    Set @blRequest = Concat("{",char(34),"long_url",char(34),": ",char(34), @urlToShorten1, char(34), ",", char(34),"group_guid",char(34),":",char(34),@group_guid,char(34),"}")
    if (_messagecontext != 'SMS') THEN
    HTTPPost2("https://api-ssl.bitly.com/v4/shorten","application/json",@blRequest,false,@blResp,@dummy,"Authorization",CONCAT("Bearer ",@access_token))
    Endif
    if (IndexOf(@blResp,Concat(char(34),"link",char(34))) == 0) then
        Set @url1 = @urlToShorten1
    else
        Set @temp = Replace(Substring(@blResp,IndexOf(@blResp,Concat(char(34),"link",char(34))),Length(@blResp)),Concat(char(34),"link",char(34),":",char(34)),"")
        Set @blEnd = Subtract(IndexOf(@temp, char(34)),1)
        Set @url1= Substring(@temp,0,@blEnd)
    endif
</script>