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TXRef conversion javascript library

About

Javascript library for Bech32 Encoded TX References, ported from Jonas Schnelli's reference implementation for the Rebooting Web Of Trust's BTCR Hackathon. It uses Peter Wuille's Bech32 library for Bech32 encoding and decoding.

For more details, see the Bech32 Encoded Transaction Position References BIP.

This implementation works as follows:

  • Encoding:

    • Given a txid and chain (testnet/mainnet), fetch the block height and position from a blockchain explorer
    • Convert to a short id as shown in btc_txref_encode

  • Decoding:

    • Decodes the bech32-encoded txref
    • Extracts the block height and position as shown in btc_txref_decode
    • Find the txid corresponding to the blockheight and position from a blockchain explorer

This library is for prototype use only. Some future improvements would include:

  • Checking confirmation count from the API results; warn if less than 6 (or some other threshold).
  • Compare results from multiple blockchain explorer APIs
  • Flexible accessor if a local bitcoin node is available.
  • Robust error checking

You can use this as a node package or in a browser. The browserified script is available as txrefConverter-browserified.js.

Preview

You can experiment with this library in the BTCR TX Playground

Examples

In these examples, note the following:

  • Prefixes: mainnet tx refs start with the tx1 prefix, whereas testnet tx refs start with txtest1

Convert a TXID to a TXref

let txrefConverter = require('./txrefConverter');

txrefConverter.txidToTxref("016b71d9ec62709656504f1282bb81f7acf998df025e54bd68ea33129d8a425b", 
    txrefConverter.CHAIN_MAINNET)
  .then(result => {
    console.log(result); // expect "tx1:rk63-uqnf-z08h-t4q"
  });

Convert a TXref to a TXID

let txrefConverter = require('./txrefConverter');

txrefToTxid("tx1:rk63-uqnf-z08h-t4q", "mainnet")
  .then(result => {
    console.log(result)
  });

Expected output:

{
  txid: '016b71d9ec62709656504f1282bb81f7acf998df025e54bd68ea33129d8a425b',
  chain: 'mainnet',
  utxoIndex: 0
}

Finer grained functions

Given the chain, block height and position, encode as a TXref

Mainnet:

let txrefConverter = require('./txrefConverter');

let result = txrefConverter.txrefEncode("mainnet", 0, 0);
console.log(result); // expect "tx1:rqqq-qqqq-qygr-lgl"

Testnet:

let txrefConverter = require('./txrefConverter');

let result = txrefConverter.txrefEncode("testnet", 1152194, 1);
console.log(result); // expect "txtest1:xyv2-xzpq-q63z-7p4"

Given a TXref, extract the chain, block height and position

let txrefConverter = require('./txrefConverter');

let result = txrefConverter.txrefDecode('tx1:rzqq-qqqq-qhlr-5ct');
console.log(result);

// Expected: { blockHeight: 1, blockIndex: 0, chain: 'mainnet', utxoIndex: 0 }

Get transaction details

Given a txid and chain, lookup the transaction details:

let txrefConverter = require('./txrefConverter');

getTxDetails("f8cdaff3ebd9e862ed5885f8975489090595abe1470397f79780ead1c7528107", "testnet")
    .then(data => {
      console.log(data.numConfirmations); // and other transaction data obtained from the explorer
      var result = txrefEncode("testnet", data.blockHeight, data.blockIndex);
      return result
    }, error => {
      console.error(error);
    });

Install

npm install

Using in a browser

npm run build generates the browserified script txrefConverter-browserified.js, which you can include in your web project.

The following shows how you can use it:

<script src="./txrefConverter-browserified.js"></script>

txrefConverter.txidToTxref(txid, chain)
  .then(function (result, err) {
      // populate widget with result
});

See the BTCR playground code repository btcr-tx-playground for working code samples.

Running tests

npm run test