Here is the the scenario.
Users come to my website and register(by using email and password). Then they login. After that, They add a new item(which has name and quantity fields). After Clicking submit, What happens is in a front-end or back-end, I generate the same amount of UUID-s that the quantity he specified. For example, if he added a new item ("Toy123", 15), I generate 15 UUID-s on that page. Then what I need to do is this user to sign these UUIDS with his private key. The thing is, I could make all 15 UUIDS into one and let user sign this final one with his private key, But I don't like this option because I need different kind of signatures for each uuids because each uuids means each item and each item is different. So what I need him to do is to sign these uuids seperatelly. I tried metamask, but It's not great, because to sign separatelly, metamask pops up a confirmation dialog for each uuids. Imagine if an user specified 150 uuids, 150 confirmation dialog? Doesn't seem great. That's why I don't want to use metamask. The second option is to ask an user for his private key and then sign each uuids programatically, but if I ask an user his private key, he is gonna be afraid.
I tried to explain the whole situation I'm facing. The question is: What do I do to sign an user's uuids separatelly with his private key without asking his private key? Is it possible with metamask?