xCall dapps on COSMWASM chains

Interacting with dApps connected with xcall requires you to be able to do the following tasks:

Call readonly methods on the specific chain.
Sign transactions invoking methods on smart contracts on the specific chain.
Fetch or listening to events being raised on smart contracts on the specific chain.

On this tutorial we are going to showcase examples on doing all of this tasks for COSMWASM chains using Javascript more specifically the cosmjs (opens in a new tab) npm package.

For more in-depth details on the code and live testing this scenario you can clone our xcall-scaffolding (opens in a new tab) repo, in there you can find an specific demo that execute all the steps for a cross-chain transaction on a JVM-COSMWASM scenario (opens in a new tab).

Sign transactions on COSMWASM chains.

Interacting with xCall dapps will require you to sign transactions for some contract methods (sendMessage, executeCall and/or executeRollback).

On COSMWASM chains this can be done using the cosmjs npm package.

The following is a code example showcasing how to sign the transaction to invoke the executeCall (execute_call on cosmwasm chains) method of the xCall contract:

import { DirectSecp256k1Wallet } from "@cosmjs/proto-signing";
import { SigningCosmWasmClient } from "@cosmjs/cosmwasm-stargate";
import { calculateFee, GasPrice } from "@cosmjs/stargate";
 
const privateKey = "0123...456";
const rpc = "https://rpc.constantine.archway.tech:443";
const xcallAdress = "archway1h04c8eqr99dnsw6wqx80juj2vtuxth70eh65cf6pnj4zan6ms4jqshc5wk":
const reqId = 122 // ID of the cross chain transaction on destination
const data = [0,2,1,...4] // data (payload) of the cross chain message of type array of integers from 0 to 255;
 
async function main() {
    const wallet = await DirectSecp256k1Wallet.fromKey(Buffer.from(privateKey, "hex"), "archway");
    const service = await SigningCosmWasmClient.connectWithSigner(rpc, wallet);
 
    const gasPrice = GasPrice.fromString("1000000000000aconst");
    const fee = calculateFee(1_000_000, gasPrice);
    const request = await service.execute(
        wallet.address,
        xcallAddress,
        {
            execute_call: {
                request_id: reqId,
                data: data
            }
        }
    );
 
    console.log("request:");
    console.log(request);
}
 
main();

Fetch and/or listening for events on smart contracts on COSMWASM chains.

Fetching the xcall specific events on a COSMWASM chain will require for you to listen for every block on the chain, fetch the transactions on the block and then make a request to get the data specific to that transaction to find out if the specific event you are waiting has been raised or not.

A detailed code implementing this event monitor can be found in the jvm-cosmwasm demo (opens in a new tab) of the xcall-scaffolding repo.

As a summary, once we found a transaction that contains our event it will look like the following:

{
  height: 3450917,
  txIndex: 0,
  hash: '1F28AC292198F1CED4B4577756A0FC919DB60D42FBB42BD42EA60584689F0673',
  code: 0,
  events: [
    { type: 'wasm-CallMessage', attributes: [Array] },
  ],
  rawLog: '....',
  tx: Uint8Array(924) [
     10, 222,   5,  10, 219,   5,  10,  36,  47,  99, 111, 115,
    109, 119,  97, 115, 109,  46, 119,  97, 115, 109,  46, 118,
     49,  46,  77, 115, 103,  69, 120, 101,  99, 117, 116, 101,
     67, 111, 110, 116, 114,  97,  99, 116,  18, 178,   5,  10,
     46,  97, 114,  99, 104, 119,  97, 121,  49,  54,  50, 120,
     50, 113, 121, 118, 113, 110, 106, 101, 116, 116, 103,  53,
    115, 116, 110, 112, 107, 102, 120,  50, 115, 101, 112, 103,
    102, 106,  56, 104, 106, 117,  51,  48,  51,  51,  48,  18,
     66,  97, 114,  99,
    ... 824 more items
  ],
  msgResponses: [],
  gasUsed: 709269n,
  gasWanted: 1066923n
}

The specific event object looks like this:

{
  type: 'wasm-CallMessage',
  attributes: [
    {
      key: '_contract_address',
      value: 'archway1h04c8eqr99dnsw6wqx80juj2vtuxth70eh65cf6pnj4zan6ms4jqshc5wk'
    },
    {
      key: 'data',
      value: '[69, 120, 101, 99, 117, 116, 101, 82, 111, 108, 108, 98, 97, 99, 107]'
    },
    {
      key: 'from',
      value: '0x2.icon/cxce68412abde16d19bff747f3e22d33e2f9315ce9'
    },
    { key: 'reqId', value: '95' },
    { key: 'sn', value: '399' },
    {
      key: 'to',
      value: 'archway1u8xcyx4x7fhvrsskwwlj4gd37ks8w0su263r2vx66nsfvlplzcgqr35cwr'
    }
  ]
}

In here, the data and reqId param are the values that we are going to be using to sign the executeCall transaction explained in the previous section about signing transactions on COSMWASM chains.

The following is a concise example of how to fetch the transaction data:

import { StargateClient } from "@cosmjs/stargate";
 
const rpc = "https://rpc.constantine.archway.tech:443";
const txHash = "0x12345...567"; // tx hash where event was raised
 
async function main() {
    const client = await StargateClient.connect(rpc);
    const tx = await client.getTx(txHash);
 
    console.log("tx data");
    console.log(tx);
}
 
main();

Interacting with xCall dApps on EVM chains Explanations