feat(abstract-utxo): support RootWalletKeys in fixedScript address generation

Support passing RootWalletKeys directly to generateAddressWithChainAndIndex
for more efficient key derivation without recreating HD nodes for each
address.

Also allows passing custom derivation prefixes which can be set inside
RootWalletKeys (defaults to /0/0/).

Issue: BTC-2668

Co-authored-by: llm-git <[email protected]>

Author: OttoAllmendinger

modules/abstract-utxo/src/address/fixedScript.ts

@@ -9,7 +9,8 @@ import {
   P2trUnsupportedError,
   P2wshUnsupportedError,
   UnsupportedAddressTypeError,
-  sanitizeLegacyPath,
+  isTriple,
+  Triple,
 } from '@bitgo/sdk-core';
 import * as utxolib from '@bitgo/utxo-lib';
 import { bitgo } from '@bitgo/utxo-lib';
@@ -52,7 +53,7 @@ function supportsAddressType(network: utxolib.Network, addressType: ScriptType2O
 
 export function generateAddressWithChainAndIndex(
   network: utxolib.Network,
-  keychains: { pub: string }[],
+  keychains: bitgo.RootWalletKeys | Triple<string>,
   chain: bitgo.ChainCode,
   index: number,
   format: CreateAddressFormat | undefined
@@ -61,24 +62,19 @@ export function generateAddressWithChainAndIndex(
     // Convert CreateAddressFormat to AddressFormat for wasm-utxo
     // 'base58' -> 'default', 'cashaddr' -> 'cashaddr'
     const wasmFormat = format === 'base58' ? 'default' : format;
-    return wasmUtxo.fixedScriptWallet.address(
-      keychains.map((k) => k.pub) as [string, string, string],
-      chain,
-      index,
-      network,
-      wasmFormat
-    );
+    return wasmUtxo.fixedScriptWallet.address(keychains, chain, index, network, wasmFormat);
+  }
+
+  if (!(keychains instanceof bitgo.RootWalletKeys)) {
+    const hdNodes = keychains.map((pub) => bip32.fromBase58(pub));
+    keychains = new bitgo.RootWalletKeys(hdNodes as Triple<utxolib.BIP32Interface>);
   }
 
-  const path = '0/0/' + chain + '/' + index;
-  const hdNodes = keychains.map(({ pub }) => bip32.fromBase58(pub));
-  const derivedKeys = hdNodes.map((hdNode) => hdNode.derivePath(sanitizeLegacyPath(path)).publicKey);
   const addressType = bitgo.scriptTypeForChain(chain);
 
+  const derivedKeys = keychains.deriveForChainAndIndex(chain, index).publicKeys;
   const { scriptPubKey: outputScript } = utxolib.bitgo.outputScripts.createOutputScript2of3(derivedKeys, addressType);
-
   const address = utxolib.address.fromOutputScript(outputScript, network);
-
   return canonicalAddress(network, address, format);
 }
 
@@ -143,7 +139,17 @@ export function generateAddress(network: utxolib.Network, params: GenerateFixedS
     }
   }
 
-  return generateAddressWithChainAndIndex(network, keychains, derivationChain, derivationIndex, params.format);
+  if (!isTriple(keychains)) {
+    throw new Error('keychains must be a triple');
+  }
+
+  return generateAddressWithChainAndIndex(
+    network,
+    keychains.map((k) => k.pub) as Triple<string>,
+    derivationChain,
+    derivationIndex,
+    params.format
+  );
 }
 
 type Keychain = {