Add encrypted storage support for embedded webview in android (#42)

Part of `MTM NYM VPN Android app`

Co-authored-by: pranavjadhav007 <jadhavpranav89@gmail.com>
Co-authored-by: Pranav <jadhavpranav89@gmail.com>
Reviewed-on: LaconicNetwork/laconic-wallet-web#42

package.json

@@ -1,6 +1,6 @@
 {
   "name": "web-wallet",
-  "version": "0.1.7-nym-0.1.2",
+  "version": "0.1.7-nym-0.1.3",
   "private": true,
   "dependencies": {
     "@cerc-io/registry-sdk": "^0.2.5",

src/global.d.ts

@@ -3,6 +3,15 @@ declare global {
   interface Window {
     // Android bridge callbacks for signature and accounts related events
     Android?: {
+      // Store a key-value pair securely in encrypted storage
+      setItem(key: string, value: string): boolean;
+
+      // Retrieve a value by key from encrypted storage
+      getItem(key: string): string | null;
+
+      // Remove a key-value pair from encrypted storage
+      removeItem(key: string): boolean;
+      
       // Called when signature is successfully generated
       onSignatureComplete?: (signature: string) => void;
 

src/utils/key-store.ts

@@ -1,13 +1,28 @@
 const setInternetCredentials = (name:string, username:string, password:string) => {
-  localStorage.setItem(name, password);
+  if (window.Android?.setItem) {
+    window.Android.setItem(name, password);
+  } else {
+    localStorage.setItem(name, password);
+  }
 };
 
 const getInternetCredentials =  (name:string) : string | null => {
-  return localStorage.getItem(name);
+  if (window.Android?.getItem) {
+    const result = window.Android.getItem(name);
+
+    // Normalize undefined to null to match localStorage behavior
+    return result === undefined ? null : result;
+  } else {
+    return localStorage.getItem(name);
+  }
 };
 
 const resetInternetCredentials = (name:string) => {
-  localStorage.removeItem(name);
+  if (window.Android?.removeItem) {
+    window.Android.removeItem(name);
+  } else {
+    localStorage.removeItem(name);
+  }
 };
 
 export {