Cross Chain Contract Calls

This guide walks you through writing our example “Call”. The goal of this guide is to show you how to conduct a cross chain contract call using ucs03-zkgm. In this case we will be calling a contract on Ethereum from Babylon.

Relevant imports will be included with each step. Outside of libraries provided by Union, this guide uses Effect.

Program

This first section is a walk through of creating the program section of the send funds example.

1. Program Declaration

Begin by using Effect to create a program function.

The signer used for this transaction is also declared here.

import { DirectSecp256k1HdWallet } from "@cosmjs/proto-signing"
import { Effect, Logger } from "effect"

const signer = await DirectSecp256k1HdWallet.fromMnemonic(
  process.env.MEMO ?? "memo memo memo",
  { prefix: "bbn" },
)

const program = Effect.gen(function*() {})

2. Source and Destination

Using the ChainRegistry from the Union TS SDK, you can declare the source and destination chains used in this example. In this case, the source is Babylon (babylon.bbn-1) and the destination is Ethereum (ethereum.1).

import { ChainRegistry } from "@unionlabs/sdk/ChainRegistry"
import { UniversalChainId } from "@unionlabs/sdk/schema/chain"
import { Effect, Logger } from "effect"

const program = Effect.gen(function*() {
  const source = yield* ChainRegistry.byUniversalId(
    UniversalChainId.make("babylon.bbn-1"),
  )

  const destination = yield* ChainRegistry.byUniversalId(
    UniversalChainId.make("ethereum.1"),
  )
})

Note

The IDs provided here are Universal Chain IDs as defined by ucs04.

3. Call

To create a Call, we supply the sender, contractAddress, and contractCalldata.

More information about Call and its fields can be found in the Call docs.

import { Call, Ucs05, ZkgmClientRequest, ZkgmClientResponse } from "@unionlabs/sdk"
import { Effect, Logger } from "effect"

const program = Effect.gen(function*() {

  // ... snip ...

  const call = Call.make({
    sender: Ucs05.CosmosDisplay.make({
      address: "bbn122ny3mep2l7nhtafpwav2y9e5jrslhekrn8frh",
    }),
    eureka: false,
    contractAddress: Ucs05.EvmDisplay.make({
      address: "0x921e5b5091f431f84f14423ec487783a853bc4b0",
    }),
    contractCalldata: "0xDEADBEEF",
  })
})

4. zkgm Request

Finally, with the Call ready - you can construct a ZkgmClientRequest.

import { Call, Ucs05, ZkgmClientRequest, ZkgmClientResponse } from "@unionlabs/sdk"
import { Effect, Logger } from "effect"

const program = Effect.gen(function*() {

  // ... snip ...

  const request = ZkgmClientRequest.make({
    source,
    destination,
    channelId: ChannelId.make(3),
    ucs03Address: "bbn1336jj8ertl8h7rdvnz4dh5rqahd09cy0x43guhsxx6xyrztx292q77945h",
    instruction: call,
  })
})

Note

ucs03 addresses can be found on the Deployments page

5. zkgm Execution and Response

Now that you’ve created a full zkgm request, you can execute it and wait on the response to close out the program.

import { Call, Ucs05, ZkgmClientRequest, ZkgmClientResponse } from "@unionlabs/sdk"
import { GasPrice } from "@cosmjs/stargate"
import { Cosmos, CosmosZkgmClient } from "@unionlabs/sdk-cosmos"
import { Effect, Logger } from "effect"
const program = Effect.gen(function*() {

  // ... snip ...

  const client = yield* CosmosZkgmClient.make.pipe(
    Effect.provide(Cosmos.SigningClient.Live(
      "bbn122ny3mep2l7nhtafpwav2y9e5jrslhekrn8frh",
      "https://rpc.bbn-1.babylon.chain.kitchen",
      signer,
      { gasPrice: GasPrice.fromString("0.0007ubbn") },
    )),
    Effect.provide(Cosmos.Client.Live("https://rpc.bbn-1.babylon.chain.kitchen")),
  )

  const response: ZkgmClientResponse.ZkgmClientResponse = yield* client.execute(request)

  yield* Effect.log("TX Hash:", response.txHash)
})

Execution

With the program ready, we can now use Effect to execute our transfer and listen for a response.

const program = Effect.gen(function*() {
  // ... program ...
}).pipe(
  Effect.provide(ChainRegistry.Default),
  Effect.provide(Logger.replace(Logger.defaultLogger, Logger.prettyLoggerDefault)),
)

Effect.runPromise(program)
  .then(console.log)
  .catch(console.error)