non-custodial liquid wallets

1 files changed, 125 insertions, 0 deletions

diff --git a/lib/buildliquidtx.js b/lib/buildliquidtx.js
new file mode 100644
index 00000000..d9b14d13
--- /dev/null
+++ b/lib/buildliquidtx.js
@@ -0,0 +1,125 @@
+const axios = require("axios");
+const liquid = require("liquidjs-lib");
+const coinselect = require("coinselect");
+const split = require("coinselect/split");
+const api = prod ? "https://blockstream.info/api" : "http://localhost:3002";
+const SATS = 100000000;
+const network = prod ? liquid.networks["liquid"] : liquid.networks["regtest"];
+
+module.exports = async ({ address, asset, amount, feeRate, user }) => {
+  const { btcasset: btc } = config.liquid;
+
+  if (!feeRate) {
+    let { feerate } = await lq.estimateSmartFee(6);
+    if (!feerate) feerate = 0.00002;
+    feeRate = feerate * SATS;
+  }
+  feeRate = Math.round(feeRate / 1000);
+  if (asset !== btc) feeRate = 0;
+
+  const payments = await db.Payment.findAll({
+    where: {
+      received: true,
+      account_id: user.account_id,
+    },
+  });
+
+  let utxos = [];
+  for (let i = 0; i < payments.length; i++) {
+    let url = `${api}/address/${payments[i].address}/utxo`;
+    try {
+      utxos.push(...(await axios.get(url)).data);
+    } catch (e) {
+      l.error("problem fetching utxos", e.message, url);
+    }
+  }
+
+  let feeInput = utxos.find((utxo) => utxo.asset === btc && utxo.value > 1000);
+  if (!feeInput) throw new Error("Couldn't find fee input");
+
+  utxos = utxos.filter((utxo) => utxo.asset === asset);
+
+  let feeChange = feeInput.value - 1000;
+
+  let targets = [
+    {
+      address,
+      value: amount,
+    },
+  ];
+
+  let { inputs, outputs, fee } = coinselect(utxos, targets, feeRate);
+
+  if (!inputs || !outputs) {
+    l.info(
+      "utxos",
+      amount,
+      feeRate,
+      utxos.map((u) => u.value),
+      inputs,
+      outputs
+    );
+    throw new Error(
+      "Couldn't find inputs for transaction, check your balance/fee"
+    );
+  }
+
+  let psbt = new liquid.Psbt({ network });
+  let total = 0;
+
+  let { address: changeAddress } = payments[payments.length - 1];
+
+  outputs.map(({ address, value }) => {
+    total += value;
+    if (!address) {
+      address = changeAddress;
+      change.push(address);
+    }
+
+    psbt = psbt.addOutput({
+      address,
+      asset,
+      value,
+    });
+  });
+
+  for (let i = 0; i < inputs.length; i++) {
+    let { txid, vout } = inputs[i];
+    psbt = psbt.addInput({
+      hash: txid,
+      index: vout,
+      nonWitnessUtxo: Buffer.from(await lq.getRawTransaction(txid), "hex"),
+    });
+  }
+
+  if (asset !== btc) {
+    l.info("feeInput", feeInput);
+    psbt.addInput({
+      hash: feeInput.txid,
+      index: feeInput.vout,
+      nonWitnessUtxo: Buffer.from(
+        await lq.getRawTransaction(feeInput.txid),
+        "hex"
+      ),
+    });
+
+    psbt.addOutput({
+      changeAddress,
+      asset: btc,
+      value: feeChange,
+    });
+  }
+
+
+    psbt.addOutput({
+      asset: btc,
+      script: Buffer.alloc(0),
+      value: fee,
+      nonce: Buffer.alloc(1, 0),
+    });
+
+  feeRate = Math.round(feeRate * 1000);
+  psbt = psbt.toBase64();
+
+  return { tx: psbt, feeRate };
+};