feat(shielded): add shielded transactions service

services/shielded-transactions.js

@@ -0,0 +1,34 @@
+// @flow
+import electronStore from '../config/electron-store';
+
+const STORE_KEY = 'SHIELDED_TRANSACTIONS';
+
+type ShieldedTransaction = {|
+  category: 'send' | 'receive',
+  time: number,
+  address: string,
+  amount: number,
+  memo: ?string,
+|};
+
+// eslint-disable-next-line
+export const listShieldedTransactions = (): Array<ShieldedTransaction> => electronStore.has(STORE_KEY) ? electronStore.get(STORE_KEY) : [];
+
+export const saveShieldedTransaction = ({
+  category,
+  time,
+  address,
+  amount,
+  memo,
+}: ShieldedTransaction): void => {
+  electronStore.set(
+    STORE_KEY,
+    listShieldedTransactions().concat({
+      category,
+      time,
+      address,
+      amount,
+      memo: memo || '',
+    }),
+  );
+};