offlineSigning.ts

import { SigningStargateClient, StdFee, coin } from "@cosmjs/stargate";
import { chains } from "chain-registry";
import { getOfflineSignerProto } from "cosmjs-utils";
import { cosmwasm } from "osmojs";
import { ExecuteMsg } from "./contracts/WbtcController.types";

const { executeContract } = cosmwasm.wasm.v1.MessageComposer.withTypeUrl;

async function main() {
  // get offline signer
  const chain = chains.find(({ chain_name }) => chain_name === "osmosis");
  if (typeof chain === "undefined") {
    throw new Error("Chain not found");
  }

  const signer = await getOfflineSignerProto({
    mnemonic: "...",
    chain,
  });

  const client = await SigningStargateClient.offline(signer);

  // specify execute msg, this will be turned into JSON bytes and passed to msgExecuteContract
  const msgIssueMintRequest: ExecuteMsg = {
    issue_mint_request: {
      amount: "100000000",
      deposit_address: "bt1q...",
      tx_id: "",
    },
  };

  // compose msg execute contract
  const encoder = new TextEncoder();
  const msgExecuteContract = executeContract({
    sender: "osmo1...",
    contract: "osmo1...",
    // encode execute msg as byte array of JSON string
    msg: encoder.encode(JSON.stringify(msgIssueMintRequest)),
    funds: [],
  });

  // specify fee (this one is arbitrary)
  const fee: StdFee = {
    amount: [coin(1000000, "uosmo")],
    gas: "1000000",
  };

  const tx = await client.sign("osmo1...", [msgExecuteContract], fee, "memo");

  console.log(tx);
}

main().catch(console.error);