How to parse changes of the balances in json of a TX?

Question

I sent 0.13 SOL from one ordinary wallet to other. There's been no interraction with a smart contract, nor was it a token but SOL sent.

Here's a part of a TX in its raw form which I've obtained via API:

"preBalances" => [
    9997940920,
    0,
    1,
    1
], 

"preTokenBalances" => [],

"postBalances" => [
    9867934320,
    130000000,
    1,
    1
], 
"postTokenBalances" => [], 

• Why are there 4 items in the preBalances and postBalances instead of 1?

• Although it's clear that one look at 130000000 as the new balance, why is this particular element? How to determine this?

What I need: given the address of a wallet, check whether it's been deposited any SOL or tokens on. In this particular case SOL

Answer 1

if you take a look at the transaction's json, you should also have an array of accounts. I think you have 4 accounts involved in your transaction (sender, receiver, and 2 solana core program account). The pre/post balance are displayed in the same order than accounts in the transaction (or instruction, i'm not sure, i have a doubt).

So you can check with the accounts array which wallet received sol / tokens.

You can also see that the first account was debited more than 0.13 sol, because there are transaction fees.

If you take a random transaction, there could be some difference in sol balance, it could also be linked to account creation. For example, if you send a token (nft, etc) to a wallet address that doesn't have the associated token account created yet, it has to be funded (0.002 sol or so).