Extract specific information from a transaction

Question

I need to extract this info from a transaction:

• from, to wallet addresses
• asset: SOL or a token (what token?)
• amount transfered
• block_timestamp

I know how to get info of a transaction - https://docs.solana.com/developing/clients/jsonrpc-api#gettransaction

{
  "jsonrpc": "2.0",
  "result": {
    "meta": {
      "err": null,
      "fee": 5000,
      "innerInstructions": [],
      "postBalances": [499998932500, 26858640, 1, 1, 1],
      "postTokenBalances": [],
      "preBalances": [499998937500, 26858640, 1, 1, 1],
      "preTokenBalances": [],
      "rewards": [],
      "status": {
        "Ok": null
      }
    },
    "slot": 430,
    "transaction": {
      "message": {
        "accountKeys": [
          "3UVYmECPPMZSCqWKfENfuoTv51fTDTWicX9xmBD2euKe",
          "AjozzgE83A3x1sHNUR64hfH7zaEBWeMaFuAN9kQgujrc",
          "SysvarS1otHashes111111111111111111111111111",
          "SysvarC1ock11111111111111111111111111111111",
          "Vote111111111111111111111111111111111111111"
        ],
        "header": {
          "numReadonlySignedAccounts": 0,
          "numReadonlyUnsignedAccounts": 3,
          "numRequiredSignatures": 1
        },
        "instructions": [
          {
            "accounts": [1, 2, 3, 0],
            "data": "37u9WtQpcm6ULa3WRQHmj49EPs4if7o9f1jSRVZpm2dvihR9C8jY4NqEwXUbLwx15HBSNcP1",
            "programIdIndex": 4
          }
        ],
        "recentBlockhash": "mfcyqEXB3DnHXki6KjjmZck6YjmZLvpAByy2fj4nh6B"
      },
      "signatures": [
        "2nBhEBYYvfaAe16UMNqRHre4YNSskvuYgx3M6E4JP1oDYvZEJHvoPzyUidNgNX5r9sTyN1J9UxtbCXy2rqYcuyuv"
      ]
    }
  },
  "blockTime": null,
  "id": 1
}

However, how to extract all the information above?

I see blockTime which may be it.

Also, preBalances and postBalances - are they the ones to calculate the balances by? Why are they arrays? What each digit correspond to? Are the digits supposed to be subtracted from as in postBalances[N] - preBalances[N]?

All in all, how to extract all the information I need?

P.S. At the moment I'm only interested in SOL and USDT/USDC assets.

Answer 1

In transaction.message you can find accountKeys those are the accounts for the postBalance and preBalance in order. This means the first preBalance and postBalance are for the first account in accountKeys.

You can get the from field by calculating postBalance - preBalance. If it's negative then the account tokens were deducted which means it's from. if it's zero then it's unchanged. If it's positive then it was transferred to (to you are looking for).

example

doing this in rust, but it's gonna be similar in typescript since they both invoke the Solana JSON RPC API.

{
account_keys: [
    ParsedAccount {
        pubkey:  "9FunJaYzY97hcTNN95mAn8iEhXQjw9NpKDmng8NYLAbt",
        writable: true,
        signer: true 
    },
    ParsedAccount {
        pubkey: "CXFCTHyuhcJL3fiFR5eRochz4k9dwzZWfLMU7knzaCp",
        writable: true,
        signer: false
    }],
}

One way to know which token is transferred is to compare the accounts to a mint you know beforehand. But make sure the transaction doesn't have multiple mints.

For the signer, a transaction can have multiple signers, they can sign a transaction of a token transfer from one token account to another. use getParsedTransaction to get the accounts that are signers or not.