refactor: move descriptor utility functions to a separate file

Issue: BTC-1348

Author: OttoAllmendinger

packages/wasm-miniscript/test/descriptorUtil.ts

@@ -0,0 +1,40 @@
+import * as utxolib from "@bitgo/utxo-lib";
+
+/** Expand a template with the given root wallet keys and chain code */
+function expand(template: string, rootWalletKeys: utxolib.bitgo.RootWalletKeys, chainCode: number) {
+  return template.replace(/\$([0-9])/g, (_, i) => {
+    const keyIndex = parseInt(i, 10);
+    if (keyIndex !== 0 && keyIndex !== 1 && keyIndex !== 2) {
+      throw new Error("Invalid key index");
+    }
+    const xpub = rootWalletKeys.triple[keyIndex].neutered().toBase58();
+    const prefix = rootWalletKeys.derivationPrefixes[keyIndex];
+    return xpub + "/" + prefix + "/" + chainCode + "/*";
+  });
+}
+
+/**
+ * Get a standard output descriptor that corresponds to the proprietary HD wallet setup
+ * used in BitGo wallets.
+ * Only supports a subset of script types.
+ */
+export function getDescriptorForScriptType(
+  rootWalletKeys: utxolib.bitgo.RootWalletKeys,
+  scriptType: utxolib.bitgo.outputScripts.ScriptType2Of3,
+  scope: "internal" | "external",
+): string {
+  const chain =
+    scope === "external"
+      ? utxolib.bitgo.getExternalChainCode(scriptType)
+      : utxolib.bitgo.getInternalChainCode(scriptType);
+  switch (scriptType) {
+    case "p2sh":
+      return expand("sh(multi(2,$0,$1,$2))", rootWalletKeys, chain);
+    case "p2shP2wsh":
+      return expand("sh(wsh(multi(2,$0,$1,$2)))", rootWalletKeys, chain);
+    case "p2wsh":
+      return expand("wsh(multi(2,$0,$1,$2))", rootWalletKeys, chain);
+    default:
+      throw new Error(`Unsupported script type ${scriptType}`);
+  }
+}

packages/wasm-miniscript/test/fixedScriptToDescriptor.ts

@@ -1,45 +1,7 @@
 import * as assert from "assert";
 import * as utxolib from "@bitgo/utxo-lib";
 import { Descriptor } from "../js";
-
-/** Expand a template with the given root wallet keys and chain code */
-function expand(template: string, rootWalletKeys: utxolib.bitgo.RootWalletKeys, chainCode: number) {
-  return template.replace(/\$([0-9])/g, (_, i) => {
-    const keyIndex = parseInt(i, 10);
-    if (keyIndex !== 0 && keyIndex !== 1 && keyIndex !== 2) {
-      throw new Error("Invalid key index");
-    }
-    const xpub = rootWalletKeys.triple[keyIndex].neutered().toBase58();
-    const prefix = rootWalletKeys.derivationPrefixes[keyIndex];
-    return xpub + "/" + prefix + "/" + chainCode + "/*";
-  });
-}
-
-/**
- * Get a standard output descriptor that corresponds to the proprietary HD wallet setup
- * used in BitGo wallets.
- * Only supports a subset of script types.
- */
-function getDescriptorForScriptType(
-  rootWalletKeys: utxolib.bitgo.RootWalletKeys,
-  scriptType: utxolib.bitgo.outputScripts.ScriptType2Of3,
-  scope: "internal" | "external",
-): string {
-  const chain =
-    scope === "external"
-      ? utxolib.bitgo.getExternalChainCode(scriptType)
-      : utxolib.bitgo.getInternalChainCode(scriptType);
-  switch (scriptType) {
-    case "p2sh":
-      return expand("sh(multi(2,$0,$1,$2))", rootWalletKeys, chain);
-    case "p2shP2wsh":
-      return expand("sh(wsh(multi(2,$0,$1,$2)))", rootWalletKeys, chain);
-    case "p2wsh":
-      return expand("wsh(multi(2,$0,$1,$2))", rootWalletKeys, chain);
-    default:
-      throw new Error(`Unsupported script type ${scriptType}`);
-  }
-}
+import { getDescriptorForScriptType } from "./descriptorUtil";
 
 const rootWalletKeys = new utxolib.bitgo.RootWalletKeys(utxolib.testutil.getKeyTriple("wasm"));
 const scriptTypes = ["p2sh", "p2shP2wsh", "p2wsh"] as const;