move getting of hidden users to utils

* get hidden user by util
* add tests for changed actions
* add tests for getting users from local storage

frontend/app/utils/get-hidden-users.test.ts

@@ -0,0 +1,33 @@
+import { LS_HIDDEN_USERS_KEY } from '@app/common/constants';
+
+import getHiddenUsers from './get-hidden-users';
+
+describe('getHiddenUsers', () => {
+  it('should get hidden users from local storage', async () => {
+    localStorage.setItem(LS_HIDDEN_USERS_KEY, JSON.stringify([]));
+    expect(getHiddenUsers()).toEqual({});
+  });
+
+  it('should return empty object with array in local storage', async () => {
+    localStorage.setItem(LS_HIDDEN_USERS_KEY, JSON.stringify([]));
+    expect(getHiddenUsers()).toEqual({});
+  });
+
+  it('should return empty object with null in local storage', async () => {
+    localStorage.setItem(LS_HIDDEN_USERS_KEY, JSON.stringify(null));
+    expect(getHiddenUsers()).toEqual({});
+  });
+
+  it('should return empty object with string in local storage', async () => {
+    localStorage.setItem(LS_HIDDEN_USERS_KEY, JSON.stringify('string'));
+    expect(getHiddenUsers()).toEqual({});
+  });
+
+  test('should return empty object and log error with invalid JSON in localStorage', async () => {
+    const consoleSpy = jest.spyOn(console, 'error').mockImplementation();
+
+    localStorage.setItem(LS_HIDDEN_USERS_KEY, '"{:"""');
+    expect(getHiddenUsers()).toEqual({});
+    expect(consoleSpy).toHaveBeenCalled();
+  });
+});

frontend/app/utils/get-hidden-users.ts

@@ -0,0 +1,17 @@
+import { User } from '@app/common/types';
+import { getItem } from '@app/common/local-storage';
+import { LS_HIDDEN_USERS_KEY } from '@app/common/constants';
+
+export default function getHiddenUsers() {
+  try {
+    const hiddenUsers: Record<string, User> = JSON.parse(getItem(LS_HIDDEN_USERS_KEY) || '{}');
+
+    if (typeof hiddenUsers === 'object' && hiddenUsers !== null && !Array.isArray(hiddenUsers)) {
+      return hiddenUsers;
+    }
+  } catch (e) {
+    console.error('incorrect hidden user data in local storage', e); // eslint-disable-line no-console
+  }
+
+  return {};
+}