feat: password-gated recovery phrase display for HD wallets (closes #161)

src/shared/wallet.js

@@ -74,6 +74,15 @@ function isValidMnemonic(mnemonic) {
     return Mnemonic.isValidMnemonic(mnemonic);
 }
 
+// Only an HD wallet has a recovery phrase. A "key" wallet holds a bare
+// private key and an "xprv" wallet an extended private key; neither can be
+// turned back into words, so neither may ever be offered the phrase display.
+// Written as an allowlist on purpose: a wallet type added later is excluded
+// until someone decides otherwise.
+function walletHasRecoveryPhrase(walletData) {
+    return !!walletData && walletData.type === "hd";
+}
+
 module.exports = {
     generateMnemonic,
     deriveAddressFromXpub,
@@ -83,4 +92,5 @@ module.exports = {
     addressFromPrivateKey,
     getSignerForAddress,
     isValidMnemonic,
+    walletHasRecoveryPhrase,
 };