I use web3 and I would like to know when somebody sent me any kind of ERC20 token. With web3, I can get the "to" and the "input" fields. With the "to", I get the contract address. With the "input", I get the recipient and the number of tokens transferred. Then, I want to spend those tokens. For that I need to connect to the contract so I need the ABI.
My questions: where can I find the ABI since I don't have the contract source ? It is possible to find the contract source ?