Add Lab 04 assignment

04-collections-clean-code/lab/README.md

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+# Social Network :speech_balloon:
+
+Тази седмица ще запретнем ръкави и създадем проста социална мрежа, която ще моделира потребители, мрежи от приятелства, постове и реакции.
+
+### Social Network
+
+В пакета `bg.sofia.uni.fmi.mjt.socialnetwork` създайте публичен клас `SocialNetworkImpl`, който има публичен конструктор по подразбиране и имплементира интерфейса `SocialNetwork`:
+
+```java
+package bg.sofia.uni.fmi.mjt.socialnetwork;
+
+import bg.sofia.uni.fmi.mjt.socialnetwork.exception.UserRegistrationException;
+import bg.sofia.uni.fmi.mjt.socialnetwork.post.Post;
+import bg.sofia.uni.fmi.mjt.socialnetwork.profile.UserProfile;
+
+import java.util.Collection;
+import java.util.Set;
+import java.util.SortedSet;
+
+public interface SocialNetwork {
+
+    /**
+     * Registers a user in the social network.
+     *
+     * @param userProfile the user profile to register
+     * @throws IllegalArgumentException  if the user profile is null
+     * @throws UserRegistrationException if the user profile is already registered
+     */
+    void registerUser(UserProfile userProfile) throws UserRegistrationException;
+
+    /**
+     * Returns all the registered users in the social network.
+     *
+     * @return unmodifiable set of all registered users (empty one if there are none).
+     */
+    Set<UserProfile> getAllUsers();
+
+    /**
+     * Posts a new post in the social network.
+     *
+     * @param userProfile the user profile that posts the content
+     * @param content     the content of the post
+     * @return the created post
+     * @throws UserRegistrationException if the user profile is not registered
+     * @throws IllegalArgumentException  if the user profile is null
+     * @throws IllegalArgumentException  if the content is null or empty
+     */
+    Post post(UserProfile userProfile, String content) throws UserRegistrationException;
+
+    /**
+     * Returns all posts in the social network.
+     *
+     * @return unmodifiable collection of all posts (empty one if there are none).
+     */
+    Collection<Post> getPosts();
+
+    /**
+     * Returns a collection of unique user profiles that can see the specified post in their feed. A
+     * user can view a post if both of the following conditions are met:
+     * <ol>
+     *     <li>The user has at least one common interest with the author of the post.</li>
+     *     <li>The user has the author of the post in their network of friends.</li>
+     * </ol>
+     * <p>
+     * Two users are considered to be in the same network of friends if they are directly connected
+     * (i.e., they are friends) or if there exists a chain of friends connecting them.
+     * </p>
+     *
+     * @param post The post for which visibility is being determined
+     * @return A set of user profiles that meet the visibility criteria (empty one if there are none).
+     * @throws IllegalArgumentException if the post is <code>null</code>.
+     */
+    Set<UserProfile> getReachedUsers(Post post);
+
+    /**
+     * Returns a set of all mutual friends between the two users.
+     *
+     * @param userProfile1 the first user profile
+     * @param userProfile2 the second user profile
+     * @return a set of all mutual friends between the two users or an empty set if there are no
+     * mutual friends
+     * @throws UserRegistrationException if any of the user profiles is not registered
+     * @throws IllegalArgumentException  if any of the user profiles is null
+     */
+    Set<UserProfile> getMutualFriends(UserProfile userProfile1, UserProfile userProfile2)
+        throws UserRegistrationException;
+
+    /**
+     * Returns a sorted set of all user profiles ordered by the number of friends they have in
+     * descending order.
+     *
+     * @return a sorted set of all user profiles ordered by the number of friends they have in
+     * descending order
+     */
+    SortedSet<UserProfile> getAllProfilesSortedByFriendsCount();
+
+}
+```
+
+### User Profile
+
+В пакетa `bg.sofia.uni.fmi.mjt.socialnetwork.profile` създайте публичен клас `DefaultUserProfile`, чрез който ще моделираме потребителите на социалната мрежа. Той трябва да има конструктор
+
+```java
+public DefaultUserProfile(String username)
+```
+
+и да имплементира интерфейса `UserProfile`:
+
+```java
+package bg.sofia.uni.fmi.mjt.socialnetwork.profile;
+
+import java.util.Collection;
+
+public interface UserProfile {
+
+    /**
+     * Returns the username of the user.
+     * Each user is guaranteed to have a unique username.
+     *
+     * @return the username of the user
+     */
+    String getUsername();
+
+    /**
+     * Returns an unmodifiable view of the user's interests.
+     *
+     * @return an unmodifiable view of the user's interests
+     */
+    Collection<Interest> getInterests();
+
+    /**
+     * Adds an interest to the user's profile.
+     *
+     * @param interest the interest to be added
+     * @return true if the interest is newly added, false if the interest is already present
+     * @throws IllegalArgumentException if the interest is null
+     */
+    boolean addInterest(Interest interest);
+
+    /**
+     * Removes an interest from the user's profile.
+     *
+     * @param interest the interest to be removed
+     * @return true if the interest is removed, false if the interest is not present
+     * @throws IllegalArgumentException if the interest is null
+     */
+    boolean removeInterest(Interest interest);
+
+    /**
+     * Return unmodifiable view of the user's friends.
+     *
+     * @return an unmodifiable view of the user's friends
+     */
+    Collection<UserProfile> getFriends();
+
+    /**
+     * Adds a user to the user's friends.
+     *
+     * @param userProfile the user to be added as a friend
+     * @return true if the user is added, false if the user is already a friend
+     * @throws IllegalArgumentException if the user is trying to add themselves as a friend,
+     *                                  or if the user is null
+     */
+    boolean addFriend(UserProfile userProfile);
+
+    /**
+     * Removes a user from the user's friends.
+     *
+     * @param userProfile the user to be removed
+     * @return true if the user is removed, false if the user is not a friend
+     * @throws IllegalArgumentException if the user is null
+     */
+    boolean unfriend(UserProfile userProfile);
+
+    /**
+     * Checks if a user is already a friend.
+     *
+     * @param userProfile the user to be checked
+     * @return true if the user is a friend, false if the user is not a friend
+     * @throws IllegalArgumentException if the user is null
+     */
+    boolean isFriend(UserProfile userProfile);
+}
+```
+
+Обърнете внимание, че приятелството в нашата социална мрежа е симетрична релация.
+
+Интересите на даден потребител се моделират от следния enum:
+
+```java
+package bg.sofia.uni.fmi.mjt.socialnetwork.profile;
+
+public enum Interest {
+    SPORTS, BOOKS, TRAVEL, MUSIC, MOVIES, GAMES, FOOD
+}
+```
+
+### Post
+
+Пост в социалнта мрежа се моделира от класа `SocialFeedPost` в пакета `bg.sofia.uni.fmi.mjt.socialnetwork.post`. Класът трябва да има конструктор
+
+```java
+public SocialFeedPost(UserProfile author, String content)
+```
+и да имплементира интерфейса
+
+```java
+package bg.sofia.uni.fmi.mjt.socialnetwork.post;
+
+import bg.sofia.uni.fmi.mjt.socialnetwork.profile.UserProfile;
+
+import java.time.LocalDateTime;
+import java.util.Map;
+import java.util.Set;
+
+public interface Post {
+
+    /**
+     * Returns the unique id of the post.
+     * Each post is guaranteed to have a unique id.
+     *
+     * @return the unique id of the post
+     */
+    String getUniqueId();
+
+    /**
+     * Returns the author of the post.
+     *
+     * @return the author of the post
+     */
+    UserProfile getAuthor();
+
+    /**
+     * Returns the date and time when the post was published.
+     * A post is published once it is created.
+     *
+     * @return the date and time when the post was published
+     */
+    LocalDateTime getPublishedOn();
+
+    /**
+     * Returns the content of the post.
+     *
+     * @return the content of the post
+     */
+    String getContent();
+
+    /**
+     * Adds a reaction to the post.
+     * If the profile has already reacted to the post, the reaction is updated to the latest one.
+     * An author of a post can react to their own post.
+     *
+     * @param userProfile  the profile that adds the reaction
+     * @param reactionType the type of the reaction
+     * @return true if the reaction is added, false if the reaction is updated
+     * @throws IllegalArgumentException if the profile is null
+     * @throws IllegalArgumentException if the reactionType is null
+     */
+    boolean addReaction(UserProfile userProfile, ReactionType reactionType);
+
+    /**
+     * Removes a reaction from the post.
+     *
+     * @param userProfile the profile that removes the reaction
+     * @return true if the reaction is removed, false if the reaction is not present
+     * @throws IllegalArgumentException if the profile is null
+     */
+    boolean removeReaction(UserProfile userProfile);
+
+    /**
+     * Returns all reactions to the post.
+     * The returned map is unmodifiable.
+     *
+     * @return an unmodifiable view of all reactions to the post
+     */
+    Map<ReactionType, Set<UserProfile>> getAllReactions();
+
+    /**
+     * Returns the count of a specific reaction type to the post.
+     *
+     * @param reactionType the type of the reaction
+     * @return the count of reactions of the specified type
+     * @throws IllegalArgumentException if the reactionType is null
+     */
+    int getReactionCount(ReactionType reactionType);
+
+    /**
+     * Returns the total count of all reactions to the post.
+     *
+     * @return the total count of all reactions to the post
+     */
+    int totalReactionsCount();
+}
+```
+
+Реакциите се моделират от следния enum:
+
+```java
+package bg.sofia.uni.fmi.mjt.socialnetwork.post;
+
+public enum ReactionType {
+    LIKE, LOVE, ANGRY, LAUGH, SAD
+}
+```
+
+### Пакети
+
+Спазвайте имената на пакетите на всички по-горе описани типове, тъй като в противен случай, решението ви няма да може да бъде автоматично тествано.
+
+```
+src
+└── bg.sofia.uni.fmi.mjt.socialnetwork
+    ├── exception
+    │      └── UserRegistrationException.java 
+    ├── post
+    │      ├── Post.java
+    │      ├── ReactionType.java
+    │      ├── SocialFeedPost.java
+    │      └── (...)
+    ├── profile
+    │      ├── DefaultUserProfile.java
+    │      ├── Interest.java
+    │      ├── UserProfile.java
+    │      └── (...)
+    ├── SocialNetwork.java
+    ├── SocialNetworkImpl.java
+    └── (...)
+```
+
+### :warning: Забележки
+
+- Не променяйте по никакъв начин интерфейсите, дадени в условието.
+- Използването на [Java Stream API](https://docs.oracle.com/en/java/javase/23/docs/api/java.base/java/util/stream/package-summary.html) и/или [lambdas](https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html) **не е разрешено**. Задачата трябва да се реши с помощта на знанията от курса до момента.