Hi
Basically the BuyEvent will be part of the transaction response so you might also get it each time the contract is called.
In Typescript you can do this:
Fuel TS SDK | Fuel Docs
To read the entire block chain for a specific contracts logs will be something to do via an indexer take a look here:
How to Index Data on the Fuel Network using Envio (SwayFarm example) - General - Fuel Network & Sway Language