Store transaction subject function

src/utils/localStorage/transactions.js

@@ -0,0 +1,19 @@
+// @flow
+import { Map } from 'immutable'
+import { load } from '~/utils/localStorage'
+
+const getSubjectKeyFrom = (safeAddress: string) => `TXS-SUBJECTS-${safeAddress}`
+
+export const storeSubject = (safeAddress: string, nonce: number, subject: string) => {
+  const key = getSubjectKeyFrom(safeAddress)
+  const subjects = load(key) || Map()
+
+  try {
+    const updatedSubjects = subjects.setIn([safeAddress, String(nonce)], subject)
+    const serializedState = JSON.stringify(updatedSubjects)
+    localStorage.setItem(key, serializedState)
+  } catch (err) {
+    // eslint-disable-next-line
+    console.log('Error storing transaction subject in localstorage')
+  }
+}