Add an OmniLayer example to tests

[caffeinum]

I wanted to use this OmniLayer protocol, but have found no examples in the whole internet. I think it would be good to include such examples in the tests.

Here's a small snippet: https://gist.github.com/caffeinum/f64a51ce55d5ac9075bb2f5f2f439c0d

[dcousens]

Undecided whether our examples are the right place for that...

[caffeinum]

That makes sense
maybe at least some reference in the OP_RETURN section. I had a hard time breaking this and wanted to share

[dcousens]

@caffeinum have you tried the new payments API? Specifically bitcoin.payments.embed?

[junderw]

@caffeinum Modified your example to work with bitcoinjs-lib v4 (Marked changes with NEW** )

const bitcoin = require('bitcoinjs-lib')
const request = require('request-promise-native')
const net = process.env.NETWORK === 'testnet'
  ? bitcoin.networks.testnet
  : bitcoin.networks.bitcoin

const API = net === bitcoin.networks.testnet
  ? `https://test-insight.swap.online/insight-api`
  : `https://insight.bitpay.com/api`

const fetchUnspents = (address) =>
  request(`${API}/addr/${address}/utxo/`).then(JSON.parse)

const broadcastTx = (txRaw) =>
  request.post(`${API}/tx/send`, {
    json: true,
    body: {
      rawtx: txRaw,
    },
  })

const createSimpleSend = async (fetchUnspents, alice_pair, recipient_address/*, amount = 10*/) => {

  const tx = new bitcoin.TransactionBuilder(net)

  const alice_p2pkh = bitcoin.payments.p2pkh({
    pubkey: alice_pair.publicKey,
    network: net
  }).address // NEW** New Payments API for p2pkh
  const unspents = await fetchUnspents(alice_p2pkh)

  const fundValue     = 546 // dust
  const feeValue      = 5000
  const totalUnspent  = unspents.reduce((summ, { satoshis }) => summ + satoshis, 0)
  const skipValue     = totalUnspent - fundValue - feeValue

  if (totalUnspent < feeValue + fundValue) {
    throw new Error(`Total less than fee: ${totalUnspent} < ${feeValue} + ${fundValue}`)
  }

  unspents.forEach(({ txid, vout }) => tx.addInput(txid, vout, 0xfffffffe))

  const simple_send = [
    "6f6d6e69", // omni
    "0000",     // version
    "00000000001f", // 31 for Tether
    "000000003B9ACA00" // amount = 10 * 100 000 000 in HEX
  ].join('')

  const data = [ Buffer.from(simple_send, "hex") ] // NEW** data must be an Array(Buffer)

  const omniOutput = bitcoin.payments.embed({ data }).output // NEW** Payments API

  tx.addOutput(recipient_address, fundValue) // should be first!
  tx.addOutput(omniOutput, 0)

  tx.addOutput(alice_p2pkh, skipValue)

  // NEW** tx.inputs was deprecated, since you use unspents 1-for-1 to make inputs I used unspents.
  unspents.forEach((unspent, index) => {
    tx.sign(index, alice_pair)
  })

  return tx
}

// Construct tx
const alice = bitcoin.ECPair.fromWIF(process.env.ALICE_WIF, net)
const bobby = bitcoin.ECPair.makeRandom({ network: net })
const amount = null // not used

// NEW** Used new payments API for bobby
const omni_tx = createSimpleSend(fetchUnspents, alice, bitcoin.payments.p2pkh({ pubkey: bobby.publicKey, network: net }).address, amount)

const auto_send = false

omni_tx.then(tx => {
  const txRaw = tx.buildIncomplete()

  console.log('hash', txRaw.getId())

  console.log(`"${txRaw.toHex()}"`)
  console.log(txRaw)

  if (auto_send) {
    broadcastTx(txRaw.toHex())
  }
})

[junderw]

@dcousens

1. if data is a Buffer, I think we should assume it should be a single push and just make it into a single item Array automatically.
2. TransactionBuilder.inputs.forEach is something I see a lot... being only used to grab the index... (a lot of people now adays hate for (var i = 0; i < x; i++) loops... lol

[dcousens]

if data is a Buffer, I think we should assume it should be a single push and just make it into a single item Array automatically.

I don't know if that is great idea...

TransactionBuilder.inputs.forEach

I don't know why.
If you had an inputs array to begin with (unspents!), you should use that no?

[junderw]

If you had an inputs array to begin with (unspents!), you should use that no?

This assumes you use all items of the Array. (array.length === txb.inputCount)

Perhaps a getter for txb.inputCount and outputCount that grabs the current count internally...

Then we could do:

Array(txb.inputCount).fill(0).forEach((item, index) => {
	console.log(index)
})

But at that point, a for loop looks cleaner and easier to understand... :-/

[dcousens]

@junderw yes, you should always use all the unspents provided. If you don't want to use them all... filter them to what you need.

See coinselect for that workflow...

[junderw]

you should always use all the unspents provided

What about when they don't have the unspents? Like a rawtx.

If we don't want them to touch the internals of Tx and Txb then how should they gather how many inputs they have?

[dcousens]

@junderw great question.
I don't know

We don't want to encourage merely iterating over the equivalent of txb.inputs, as, it means they might not have checked what those inputs are...

[junderw]

PSBT to the rescue!

[dcousens]

@junderw is it though?