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This tutorial walks you through creating a developer-controlled wallet to sign transactions on NEAR.

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Prerequisites

Before you begin:

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Step 1. Create NEAR wallets

When creating a developer-controlled wallet, pass NEAR-TESTNET or NEAR in the blockchains field. This wallet can be used to sign transactions on NEAR. The following example code shows how to create a wallet using the Circle Developer SDK. 
const response = await circleDeveloperSdk.createWallets({
  accountType: "EOA",
  blockchains: ["NEAR-TESTNET"],
  count: 2,
  walletSetId: "<wallet-set-id>",
});
You must send NEAR tokens to activate the wallet. Without NEAR tokens in the wallet, you will receive an error stating that the account does not exist when broadcasting a transaction.
Use count to specify the number of wallets to create, up to a maximum of 200 per API request.

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Step 2. Build and sign a raw transaction

To build a raw transaction for signing in JavaScript:
  1. Prepare the transaction object - To build a NEAR transaction, you must define several parameters, including the sender, receiver, amount, actions, nonce, and any additional metadata required.
  2. Serialize the transaction object with Borsh and encode it with Base64 - NEAR uses Borsh serialization for transaction objects, so you need to serialize the constructed transaction and then encode it to Base64 before signing.
The following example code shows how to build a raw transaction for signing. 
import { initiateDeveloperControlledWalletsClient } from "@circle-fin/developer-controlled-wallets";
import { connect, utils } from "near-api-js";
import { baseDecode, baseEncode } from "@near-js/utils";
import { PublicKey } from "@near-js/crypto";
import {
  createTransaction,
  actionCreators,
  encodeTransaction,
} from "@near-js/transactions";
import axios from "axios";
import fs from "fs";

const NEAR_CONFIG = {
  networkId: "testnet",
  nodeUrl: "https://rpc.testnet.near.org",
};

// fill in these variables
const CIRCLE_API_KEY = "";
const CIRCLE_ENTITY_SECRET = "";
const CIRCLE_WALLET_PUBLIC_KEY = ""; // with `ed25519:` scheme
const CIRCLE_WALLET_ID = "";
const CIRCLE_TX_MEMO = "";
const MASTER_ACCOUNT = "";
const RECEIVER = "";
const AMOUNT = "0.001";

async function main() {
  const client = initiateDeveloperControlledWalletsClient({
    apiKey: CIRCLE_API_KEY,
    entitySecret: CIRCLE_ENTITY_SECRET,
  });

  try {
    // setup client and account
    const near = await connect({ ...NEAR_CONFIG });
    const sender = await near.account(MASTER_ACCOUNT);

    // get latest finalized block
    const block = await near.connection.provider.block({ finality: "final" });
    const blockHash = block.header.hash;

    // get sender nonce
    const senderAccessKey = await sender.getAccessKeys();
    let nonce = BigInt(0);
    for (let i = 0; i < senderAccessKey.length; i++) {
      if (senderAccessKey[i].public_key === CIRCLE_WALLET_PUBLIC_KEY) {
        nonce = senderAccessKey[i].access_key.nonce + BigInt(1);
      }
    }
    if (nonce === BigInt(0)) {
      console.error(
        `couldn't find corresponding access key: ${CIRCLE_WALLET_PUBLIC_KEY}`,
      );
      return;
    }

    // build raw transaction
    const actions = [
      actionCreators.transfer(
        BigInt(utils.format.parseNearAmount(AMOUNT) || 0),
      ),
    ];
    const signerPublicKey = PublicKey.fromString(CIRCLE_WALLET_PUBLIC_KEY);
    const transaction = createTransaction(
      MASTER_ACCOUNT,
      signerPublicKey,
      RECEIVER,
      nonce,
      actions,
      baseDecode(blockHash),
    );

    // serialize borsh
    const message = encodeTransaction(transaction);

    // base64 encode
    const base64EncodedTx = Buffer.from(message).toString("base64");

    // call Circle's API to sign tx
    const signedTx = await client.signTransaction({
      walletId: CIRCLE_WALLET_ID,
      rawTransaction: base64EncodedTx,
      memo: CIRCLE_TX_MEMO,
    });
  } catch (err) {
    if (axios.isAxiosError(err)) {
      console.error(`status: ${err.response?.status}`);
      console.error(`data: `, err.response?.data);
    } else {
      console.error(`unknown err: `, err);
    }
  }
}

(async () => {
  await main();
})();