Check uploaded zip file for a chat format text file in a user friendly way

[uptoratlen]

Currently the uploaded zip need to contain a certain named text file "_chat.txt".
This is for users not very friendly.
Suggestions (2)
a) Create a list of chat file constants (pattern) and check of such a file, in case non of the list is found, return a error (with the list so the user could check )
b) Check all uploaded text files (extension .txt) for a Whatsapp pattern (first line) , in case line of that checked file matches a WA line pattern, use it as input file; otherwise return something like "No, valid chat file found in zip."

What do you think? A even better/smarter way to get more user friendly?
Please share your thoughts on this.