buildBaseTx-avax.ts

import { Avalanche, BN, Buffer } from "avalanche/dist"
import {
  AVMAPI,
  KeyChain,
  UTXOSet,
  UnsignedTx,
  Tx,
  KeyPair,
  SelectCredentialClass
} from "avalanche/dist/apis/avm"
import {
  GetBalanceResponse,
  GetUTXOsResponse
} from "avalanche/dist/apis/avm/interfaces"
import { Defaults } from "avalanche/dist/utils"
import {
  PrivateKeyPrefix,
  DefaultLocalGenesisPrivateKey,
  DefaultEVMLocalGenesisPrivateKey,
  UnixNow
} from "avalanche/dist/utils"
import createHash from "create-hash"
import { Signature, Credential } from "avalanche/dist/common/credentials"

const ip: string = "api.avax-test.network/ext/bc/X"
const port: number = 443
const protocol: string = "https"
const networkID: number = 5
const xBlockchainID: string = Defaults.network[networkID].X.blockchainID
const avaxAssetID = Defaults.network[networkID].X.avaxAssetID as string
const avalanche: Avalanche = new Avalanche(
  ip,
  port,
  protocol,
  networkID,
  xBlockchainID
)
const xchain: AVMAPI = avalanche.XChain()
const xKeychain: KeyChain = xchain.keyChain()
const privKey: string = `${PrivateKeyPrefix}${DefaultLocalGenesisPrivateKey}`
// this is an example of a single privkey string in hex format
const privKeyStr: string = `${DefaultEVMLocalGenesisPrivateKey}`
xKeychain.importKey(privKey)
const xAddressStrings: string[] = xchain.keyChain().getAddressStrings()
const asOf: BN = UnixNow()
const threshold: number = 1
const locktime: BN = new BN(0)
const memo: Buffer = Buffer.from("AVM utility method buildBaseTx to send AVAX")
const fee: BN = xchain.getDefaultTxFee()

const main = async (): Promise<any> => {
  const getBalanceResponse: GetBalanceResponse = await xchain.getBalance(
    xAddressStrings[0],
    avaxAssetID
  )
  const balance: BN = new BN(getBalanceResponse.balance)
  const avmUTXOResponse: GetUTXOsResponse = await xchain.getUTXOs(
    xAddressStrings
  )
  const utxoSet: UTXOSet = avmUTXOResponse.utxos
  const amount: BN = balance.sub(fee)

  const unsignedTx: UnsignedTx = await xchain.buildBaseTx(
    utxoSet,
    amount,
    avaxAssetID,
    xAddressStrings,
    xAddressStrings,
    xAddressStrings,
    memo,
    asOf,
    locktime,
    threshold
  )

  // create a keypair which we'll soon over write with importKey
  const hrp: string = 'fuji'
  const chainID: string = "2JVSBoinj9C2J33VntvzYtVJNZdN2NKiwwKjcumHUWEb5DbBrm"
  const keypair: KeyPair = new KeyPair(hrp, chainID)

  // remove 0x from hex string
  const substring: string = privKeyStr.slice(2)
  const privKey: Buffer = Buffer.from(substring, "hex")
  // import the single hex privkey to create a keypair
  keypair.importKey(privKey)

  const txbuff = unsignedTx.toBuffer()
  const msg: Buffer = Buffer.from(
    createHash("sha256").update(txbuff).digest()
  )
  // this example works only if you have a single output with a single signature. If you have more complex transactions
  // such as multiple outputs or multisig then this example will not work and you'll need to 
  // expand it based on how it works here
  // the X-Chain has SECP assets and NFT assets. The SECP asset credential ID is 9
  const secpCredentialID: number = 9
  const cred: Credential = SelectCredentialClass(secpCredentialID)
  const signval: Buffer = keypair.sign(msg)
  const sig: Signature = new Signature()
  sig.fromBuffer(signval)
  const creds: Credential[] = []
  cred.addSignature(sig)
  creds.push(cred)
  const tx: Tx = new Tx(unsignedTx, creds)
  const txid: string = await xchain.issueTx(tx)
  console.log(`Success! TXID: ${txid}`)
}

main()