Hi there,
I will be happy to help you adding these functionalities to the Google script that you already have running. The script will parse the body of the email that you send to find the invoice issue date, company and document number, then it will rename the attachment file in the required format, invoicedate_companyname_documentnumber.pdf. If a file with the same name already exists, the file won't be saved.
I do have the required experience, all of my previous projects are Google script projects.
I will be happy to discuss more details with you!
Sincerely,
Mohamed