feat(utxo-staking): build staking transaction

TICKET: BTC-1579

modules/utxo-staking/src/index.ts

@@ -1 +1,3 @@
 export * as coreDao from './coreDao';
+
+export * from './transaction';

modules/utxo-staking/src/transaction.ts

@@ -0,0 +1,100 @@
+import * as utxolib from '@bitgo/utxo-lib';
+import { Dimensions } from '@bitgo/unspents';
+
+/**
+ * Build a staking transaction for a wallet that assumes 2-of-3 multisig for the inputs
+ *
+ * Given the inputs and the staking outputs, we will create the PSBT with the desired fee rate.
+ * We always add the change address as the last output.
+ *
+ * @param rootWalletKeys
+ * @param unspents
+ * @param createStakingOutputs
+ * @param changeAddressInfo
+ * @param feeRateSatKB
+ * @param network
+ */
+export function buildFixedWalletStakingPsbt({
+  rootWalletKeys,
+  unspents,
+  outputs,
+  changeAddressInfo,
+  feeRateSatKB,
+  network,
+  skipNonWitnessUtxo,
+  dustAmount = BigInt(0),
+}: {
+  rootWalletKeys: utxolib.bitgo.RootWalletKeys;
+  unspents: utxolib.bitgo.WalletUnspent<bigint>[];
+  outputs: {
+    script: Buffer;
+    value: bigint;
+  }[];
+  changeAddressInfo: {
+    chain: utxolib.bitgo.ChainCode;
+    index: number;
+    address: string;
+  };
+  feeRateSatKB: number;
+  network: utxolib.Network;
+  skipNonWitnessUtxo?: boolean;
+  dustAmount?: bigint;
+}): utxolib.bitgo.UtxoPsbt {
+  if (feeRateSatKB < 1000) {
+    throw new Error('Fee rate must be at least 1 sat/vbyte');
+  }
+  if (unspents.length === 0 || outputs.length === 0) {
+    throw new Error('Must have at least one input and one output');
+  }
+
+  // Check the change address info
+  const changeScript = utxolib.bitgo.outputScripts.createOutputScript2of3(
+    rootWalletKeys.deriveForChainAndIndex(changeAddressInfo.chain, changeAddressInfo.index).publicKeys,
+    utxolib.bitgo.scriptTypeForChain(changeAddressInfo.chain),
+    network
+  ).scriptPubKey;
+  if (!changeScript.equals(utxolib.addressFormat.toOutputScriptTryFormats(changeAddressInfo.address, network))) {
+    throw new Error('Change address info does not match the derived change script');
+  }
+
+  const psbt = utxolib.bitgo.createPsbtForNetwork({ network });
+  utxolib.bitgo.addXpubsToPsbt(psbt, rootWalletKeys);
+
+  const inputAmount = unspents.reduce((sum, unspent) => sum + unspent.value, BigInt(0));
+  const outputAmount = outputs.reduce((sum, output) => sum + output.value, BigInt(0));
+
+  unspents.forEach((unspent) =>
+    utxolib.bitgo.addWalletUnspentToPsbt(psbt, unspent, rootWalletKeys, 'user', 'bitgo', {
+      isReplaceableByFee: true,
+      skipNonWitnessUtxo,
+    })
+  );
+  outputs.forEach((output) => psbt.addOutput(output));
+
+  const fee = Math.ceil(
+    (Dimensions.fromPsbt(psbt)
+      .plus(Dimensions.fromOutput({ script: changeScript }))
+      .getVSize() *
+      feeRateSatKB) /
+      1000
+  );
+
+  const changeAmount = inputAmount - (outputAmount + BigInt(fee));
+  if (changeAmount < BigInt(0)) {
+    throw new Error(
+      `Input amount ${inputAmount.toString()} cannot cover the staking amount ${outputAmount} and  the fee: ${fee}`
+    );
+  }
+
+  if (changeAmount > dustAmount) {
+    utxolib.bitgo.addWalletOutputToPsbt(
+      psbt,
+      rootWalletKeys,
+      changeAddressInfo.chain,
+      changeAddressInfo.index,
+      changeAmount
+    );
+  }
+
+  return psbt;
+}

modules/utxo-staking/test/unit/transaction.ts

@@ -0,0 +1,109 @@
+import * as assert from 'assert';
+
+import * as utxolib from '@bitgo/utxo-lib';
+import { buildFixedWalletStakingPsbt } from '../../src';
+
+describe('transactions', function () {
+  describe('fixed wallets', function () {
+    const rootWalletKeys = utxolib.testutil.getDefaultWalletKeys();
+    const network = utxolib.networks.bitcoin;
+    const chain = 20;
+    const index = 0;
+    const changeAddress = utxolib.address.fromOutputScript(
+      utxolib.bitgo.outputScripts.createOutputScript2of3(
+        rootWalletKeys.deriveForChainAndIndex(chain, index).publicKeys,
+        'p2wsh',
+        network
+      ).scriptPubKey,
+      network
+    );
+    const changeAddressInfo = { chain: chain as utxolib.bitgo.ChainCode, index, address: changeAddress };
+
+    const unspents = utxolib.testutil.mockUnspents(
+      rootWalletKeys,
+      ['p2sh', 'p2wsh'],
+      BigInt(1e8),
+      network
+    ) as utxolib.bitgo.WalletUnspent<bigint>[];
+
+    const outputs = [
+      {
+        script: utxolib.bitgo.outputScripts.createOutputScript2of3(
+          rootWalletKeys.deriveForChainAndIndex(40, 0).publicKeys,
+          'p2trMusig2',
+          network
+        ).scriptPubKey,
+        value: BigInt(1e7),
+      },
+    ];
+
+    it('should fail if fee rate is negative', function () {
+      assert.throws(() => {
+        buildFixedWalletStakingPsbt({
+          rootWalletKeys,
+          unspents,
+          outputs,
+          changeAddressInfo,
+          feeRateSatKB: 999,
+          network,
+        });
+      }, /Fee rate must be at least 1 sat\/vbyte/);
+    });
+
+    it('should fail if the changeAddressInfo does not match the derived change script', function () {
+      assert.throws(() => {
+        buildFixedWalletStakingPsbt({
+          rootWalletKeys,
+          unspents,
+          outputs,
+          changeAddressInfo: { ...changeAddressInfo, index: 1 },
+          feeRateSatKB: 1000,
+          network,
+        });
+      }, /Change address info does not match the derived change script/);
+    });
+
+    it('should fail if there are no unspents or outputs', function () {
+      assert.throws(() => {
+        buildFixedWalletStakingPsbt({
+          rootWalletKeys,
+          unspents: [],
+          outputs: [],
+          changeAddressInfo,
+          feeRateSatKB: 1000,
+          network,
+        });
+      }, /Must have at least one input and one output/);
+    });
+
+    it('should fail if the input amount cannot cover the staking amount and the fee', function () {
+      assert.throws(() => {
+        buildFixedWalletStakingPsbt({
+          rootWalletKeys,
+          unspents: unspents.slice(0, 1),
+          outputs: [
+            { script: outputs[0].script, value: unspents.reduce((sum, unspent) => sum + unspent.value, BigInt(0)) },
+          ],
+          changeAddressInfo,
+          feeRateSatKB: 1000,
+          network,
+        });
+      }, /Input amount \d+ cannot cover the staking amount \d+ and  the fee: \d+/);
+    });
+
+    it('should be able to create a psbt for a fixed wallet', function () {
+      const psbt = buildFixedWalletStakingPsbt({
+        rootWalletKeys,
+        unspents,
+        outputs,
+        changeAddressInfo,
+        feeRateSatKB: 1000,
+        network,
+      });
+
+      assert.deepStrictEqual(psbt.data.inputs.length, 2);
+      assert.deepStrictEqual(psbt.data.outputs.length, 2);
+      assert.deepStrictEqual(psbt.txOutputs[0].script, outputs[0].script);
+    });
+  });
+});