Develop a solana program to swap tokens

Hi,

I am working on a dapp and one of the requirements is that, tokens need to be swapped in the backend. When a certain threshold that was set by the user, the tokens will be swapped automatically and in this case, the user might not be available to sign the transaction. So, I need to make the swap either by asking the user to sign beforehand, or, I was wondering if it is possible to do an on-chain swap? Like, developing a program that swaps tokens. Is it possible to develop a program that swaps tokens in solana?