Answer Happy

Task
For this challenge, you are going to build a mock comments section.
Design
The design will focus on two base classes:
Users
Users come in 3 flavors: normal users, moderators and admins. Normal users can only create new comments and edit the their own comments. Moderators have the added ability to delete comments, while admins have the ability to edit or delete any comment.
Users can log in and out, and we track when they last logged in
Comments
Comments contain fields for a message, a timestamp and an author.
Comments can also be a reply, so we'll store a reference to the parent comment if it exists.
Your Challenge
This is challenge is not about building a fully functional API, but more about focusing on the design from an object-oriented point-of-view.
We've provided the basic API (which is incomplete), which we would like you to complete being aware of the following Object-Oriented Programming concepts:
Encapsulation of Properties
The method-based API is provided. These must be completed as-is.
Additional methods are allowed, though remember to keep read-only properties read-only.
Instantiation
Classes should be instantiated with properties (as provided), to create instances with values already assigned.
User/Moderator/Admin defaults:
Should be marked as not logged in
Should return null for the last logged in at property
Comment defaults:
Should set the current timestamp for the created at property upon instantiation
Replied To is optional, and should be null if not provided.
Inheritance & Access Control
Note: for the sake of simplicity, you can simply treat object equality as "equal", though more complete solutions will also pass.
User
Users can be logged in and out.
When logging in, set the lastLoggedInAt timestamp. Do not modify this timestamp when logging out
Users can only edit their own comments
Users cannot delete any comments
Moderator is a User
Moderators can only edit their own comments
Moderators can delete any comments
Admin is both a User and a Moderator
Admins can edit any comments
Admins can delete any comments
Composition
Comments contain a reference to the User who created it (author)
Comments optionally contain a reference to another comment (repliedTo)
When converting to a string (toString), the following format is used:No replied to:
With replied to:
Note
Due to the incomplete nature of the starter code in this challenge, the test suite will fail to compile--this is normal; you may need to comment out portions of the test suite to verify your solution as you work.
Code Below
import java.util.Date;
public class Solution { public static class User { public User(String name) {} public boolean isLoggedIn() {} public Date getLastLoggedInAt() {} public void logIn() {} public void logOut() {} public String getName() {} public void setName(String name) {} public boolean canEdit(Comment comment) {} public boolean canDelete(Comment comment) {} } public static class Moderator { public Moderator(String name) {} } public static class Admin { public Admin(String name) {} } public static class Comment { public Comment(User author, String message) {} public Comment(User author, String message, Comment repliedTo) {} public String getMessage() {} public void setMessage(String message) {} public Date getCreatedAt() {} public User getAuthor() {} public Comment getRepliedTo() {} public String toString() {} }}