hcs/getTopicMessages

How to call the API from an app

Hedera Wallet Snap connects to your currently connected Metamask account by default. To learn how apps can connect to Hedera Wallet Snap using a non-metamask(external) account, refer to this documentation.

Then, depending on whether you're trying to connect to a metamask account or a non-metamask account, you can call the snap API in the following way:

const snapId = `npm:@hashgraph/hedera-wallet-snap`

const snapAPI = async () => {
  const externalAccountParams = {
    externalAccount: {
      accountIdOrEvmAddress: '0.0.12345',
      curve: 'ED25519'
    }
  }

  await window.ethereum.request({
    method: 'wallet_invokeSnap',
    params: {
      snapId,
      request: {
        method: 'hcs/getTopicMessages',
        params: {
          network: 'testnet',
          topicId: '0.0.4617270',
          sequenceNumber?, // Optional param - type: number
          /* 
            Uncomment the below line if you want to connect 
            to a non-metamask account
          */
          // ...externalAccountParams
        }
      }
    }
  })
}

What the API does

  1. Retrieves the currently connected account the user has selected on Metamask. If it's the first time, a new snap account is created and the account info is saved in snap state.

  2. Parses the arguments that were passed.

  3. Calls the Hedera Mirror Node Get Topic Messages API to retrieve messages written to the topic from a mirror node.

  4. Returns the transaction receipt as response

An example response:

{
    "currentAccount": {
        "metamaskEvmAddress": "0x0b3628d1b838993b5fceec8b2a26502e7a8e5241",
        "externalEvmAddress": "",
        "hederaAccountId": "0.0.3581604",
        "hederaEvmAddress": "0xca53f9c93d30e0b7212d67901e5a24fb090d542b",
        "publicKey": "0x0206022cea4c6dd6d2e7263b8802253971de922f5380661d97cba82dee66f57ad6",
        "balance": {
            "hbars": 86.77513646,
            "timestamp": "Tue, 23 Jul 2024 18:34:03 GMT",
            "tokens": {
                "0.0.4284934": {
                    "balance": 0,
                    "decimals": 1,
                    "tokenId": "0.0.4284934",
                    "name": "Pulse",
                    "symbol": "PULSE",
                    "tokenType": "FUNGIBLE_COMMON",
                    "supplyType": "INFINITE",
                    "totalSupply": "0",
                    "maxSupply": "0"
                }
            }
        },
        "network": "testnet",
        "mirrorNodeUrl": "https://testnet.mirrornode.hedera.com"
    },
    "topicMessages": [
        {
            "chunk_info": {
                "initial_transaction_id": {
                    "account_id": "0.0.3581604",
                    "nonce": 0,
                    "scheduled": false,
                    "transaction_valid_start": "Tue, 23 Jul 2024 18:33:50 GMT"
                },
                "number": 1,
                "total": 1
            },
            "consensus_timestamp": "Tue, 23 Jul 2024 18:34:03 GMT",
            "message": "Zmlyc3QgbWVzc2FnZQ==",
            "payer_account_id": "0.0.3581604",
            "running_hash": "u6lxAMZ0d19vh2GCc5gNGClxzqQeK2Zd7TZorA2WiaaKGlENN7nYtDAktM+0Ly7T",
            "running_hash_version": 3,
            "sequence_number": 1,
            "topic_id": "0.0.4617270"
        }
    ]
}

Live Demo on CodePen

Last updated

Was this helpful?