stuff

0-Plugin/src/main/java/cli/Subcommand.java

@@ -21,7 +21,7 @@ abstract public class Subcommand {
 			commandExists(args[0]);
 			return commands.get(args[0]).apply(args);
 		}
-		catch (IndexOutOfBoundsException e) {
+		catch (IndexOutOfBoundsException | IllegalArgumentException e) {
 			throw new CliError("Missing a value! " + getUsage());
 		}
 	}

0-Plugin/src/main/java/cli/link/LinkCommands.java

@@ -16,6 +16,7 @@ public class LinkCommands extends Subcommand {
 		commands.put("category", this::getByCategory);
 		commands.put("user", this::getByUser);
 		commands.put("tag", this::getByTag);
+		commands.put("hosts", this::groupByHosts);
 	}
 
 	@Override
@@ -30,7 +31,9 @@ public class LinkCommands extends Subcommand {
 				getSubcommand() + " get " + System.lineSeparator() +
 				getSubcommand() + " category aCategoryName " + System.lineSeparator() +
 				getSubcommand() + " tag aTagName " + System.lineSeparator() +
-                getSubcommand() + "user aUserName ";
+				getSubcommand() + " user aUserName " + System.lineSeparator() +
+				getSubcommand() + " hosts";
+
 	}
 
 	private String addLink(String[] args) {
@@ -41,18 +44,27 @@ public class LinkCommands extends Subcommand {
 	}
 
 	private String getAll(String[] args) {
-        return String.join(System.lineSeparator(), linkCliAdapter.getLinks());
+		var firstLine = "All available Links:" + System.lineSeparator();
+		return firstLine + String.join(System.lineSeparator(), linkCliAdapter.getLinks());
 	}
 
 	private String getByCategory(String[] args) {
-        return String.join(System.lineSeparator(), linkCliAdapter.getLinksForCategory(args[1]));
+		var firstLine = "All available Links for the category:" + System.lineSeparator();
+		return firstLine + String.join(System.lineSeparator(), linkCliAdapter.getLinksForCategory(args[1]));
 	}
 
 	private String getByUser(String[] args) {
-        return String.join(System.lineSeparator(), linkCliAdapter.getLinksForUser(args[1]));
+		var firstLine = "All available Links for the user:" + System.lineSeparator();
+		return firstLine + String.join(System.lineSeparator(), linkCliAdapter.getLinksForUser(args[1]));
 	}
 
 	private String getByTag(String[] args) {
-        return String.join(System.lineSeparator(), linkCliAdapter.getLinksForTag(args[1]));
+		var firstLine = "All available Links for the tag:" + System.lineSeparator();
+		return firstLine + String.join(System.lineSeparator(), linkCliAdapter.getLinksForTag(args[1]));
+	}
+
+	private String groupByHosts(String[] strings) {
+		var firstLine = "All available Links grouped by the host names:" + System.lineSeparator();
+		return firstLine + String.join(System.lineSeparator(), linkCliAdapter.groupByHosts());
 	}
 }

0-Plugin/src/main/java/cli/tag/TagCommands.java

@@ -30,6 +30,7 @@ public class TagCommands extends Subcommand {
     }
 
     private String getTags(String[] args) {
-        return String.join(System.lineSeparator(), customTagsCliAdapter.getAllTagNames());
+        var firstLine = "All available Tags:" + System.lineSeparator();
+        return firstLine + String.join(System.lineSeparator(), customTagsCliAdapter.getAllTagNames());
     }
 }

0-Plugin/src/main/java/main/Main.java

@@ -19,6 +19,5 @@ public class Main {
 		catch (RuntimeException runtimeException) {
 			System.out.println(runtimeException.getMessage());
 		}
-
 	}
 }

1-Adapter/src/main/java/cli/link/LinkCliAdapter.java

@@ -7,6 +7,7 @@ import link.LinkUseCase;
 import tag.TagName;
 import user.Username;
 
+import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -39,4 +40,8 @@ public class LinkCliAdapter {
     public Set<String> getLinksForUser(String userName) {
         return linkUseCase.getLinksForUser(new Username(userName)).stream().map(LinkDto::toString).collect(Collectors.toSet());
     }
+
+    public List<String> groupByHosts() {
+        return linkUseCase.groupByHosts().stream().map(LinkDto::toString).collect(Collectors.toList());
+    }
 }

1-Adapter/src/main/java/persistence/link/LinkEntity.java

@@ -33,13 +33,13 @@ public class LinkEntity implements CSVSerializable {
 		this.id = Integer.parseInt(fields[0]);
 		this.creator = fields[1];
 		this.url = fields[2];
-		this.categoryIds =
+		this.categoryIds = fields.length > 3 ?
 				(Arrays.stream(fields[3].split(CSVSerializable.listSeperator)).map(Integer::parseInt)).collect(
-						Collectors.toSet());
+						Collectors.toSet()) : Set.of();
 
-		this.tags = (Arrays
+		this.tags = fields.length > 4 ?  (Arrays
 				.stream(fields[4].split(CSVSerializable.listSeperator))
-				.map(TagEntity::new)).collect(Collectors.toSet());
+				.map(TagEntity::new)).collect(Collectors.toSet()) : Set.of();
 	}
 
 	public LinkEntity(Link link) {

2-Application/src/main/java/link/LinkUseCase.java

@@ -10,11 +10,13 @@ import tag.TagName;
 import tag.TaggingUseCase;
 import user.Username;
 
+import java.util.List;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
 public class LinkUseCase {
+
 	private final LinkRepository linkRepository;
 	private final CategoryRepository categoryRepository;
 	private final TaggingUseCase taggingUseCase;
@@ -41,22 +43,30 @@ public class LinkUseCase {
 		linkRepository.add(link);
 	}
 
-
 	public Set<LinkDto> getLinks() {
 		return linkRepository.getAll().stream().map(this::convertLink).collect(Collectors.toSet());
 	}
 
 	public Set<LinkDto> getLinksForCategory(CategoryName categoryName) {
-        return linkRepository.getByCategory(categoryRepository.getIdByName(categoryName).id()).stream().map(this::convertLink).collect(Collectors.toSet());
+		return linkRepository
+				.getByCategory(categoryRepository.getIdByName(categoryName))
+				.stream()
+				.map(this::convertLink)
+				.collect(Collectors.toSet());
 	}
 
 	public Set<LinkDto> getLinksForTag(TagName tagName) {
 		return linkRepository.getByTag(tagName).stream().map(this::convertLink).collect(Collectors.toSet());
 	}
+
 	public Set<LinkDto> getLinksForUser(Username username) {
 		return linkRepository.getByUser(username).stream().map(this::convertLink).collect(Collectors.toSet());
 	}
 
+	public List<LinkDto> groupByHosts() {
+		return linkRepository.groupByHost().stream().map(this::convertLink).collect(Collectors.toList());
+	}
+
 	private LinkDto convertLink(Link link) {
 		return new LinkDto(link.getCreator(), link.getUrl(), getCategoriesOf(link), link.getTags());
 	}
@@ -71,4 +81,5 @@ public class LinkUseCase {
 				.orElseThrow(() -> new CategroyDoesNotExist(
 						"A Category for a certain id does not exits. You must create it first."));
 	}
+
 }

2-Application/src/main/java/link/RandomLinkIdGenerator.java

@@ -1,13 +1,13 @@
 package link;
 
-public class RandomLinkIdGenerator implements LinkIdGenerator {
+public class RandomLinkIdGenerator {
+
 	private final LinkRepository linkRepository;
 
 	public RandomLinkIdGenerator(LinkRepository linkRepository) {
 		this.linkRepository = linkRepository;
 	}
 
-	@Override
 	public LinkId generateId() {
 		var randomID = (int) (Math.random() * 10000);
 

3-Domain/src/main/java/link/Link.java

@@ -2,6 +2,7 @@ package link;
 
 import category.CategoryId;
 import tag.Tag;
+import tag.TagName;
 import user.Username;
 
 import java.util.Set;
@@ -34,10 +35,22 @@ public class Link {
 		return url;
 	}
 
+	public boolean hasCategoryId(CategoryId categoryId) {
+		return categoryIds.contains(categoryId);
+	}
+
 	public Set<CategoryId> getCategoryIds() {
 		return categoryIds;
 	}
 
+	public boolean hasTagName(TagName tagName) {
+		return tags.stream().anyMatch(tag -> tag.getName().equals(tagName));
+	}
+
+	public boolean wasCreatedBy(Username username) {
+		return this.creator.equals(username);
+	}
+
 	public Set<Tag> getTags() {
 		return tags;
 	}

3-Domain/src/main/java/link/LinkRepository.java

@@ -2,12 +2,15 @@ package link;
 
 import abstraction.CustomSetPersistenceDecorator;
 import abstraction.PersistenceAdapter;
+import category.CategoryId;
 import datastructures.set.CustomSet;
 import exeptions.LinkAlreadyExists;
 import exeptions.LinkDoesNotExist;
 import tag.TagName;
 import user.Username;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -63,15 +66,36 @@ public class LinkRepository {
 		}
 	}
 
-    public Set<Link> getByCategory(int id) {
-        return links.stream().filter(it -> it.getCategoryIds().contains(id)).collect(Collectors.toSet());
+	public Set<Link> getByCategory(CategoryId id) {
+		return links.stream().filter(link -> link.hasCategoryId(id)).collect(Collectors.toSet());
 	}
 
 	public Set<Link> getByTag(TagName tagName) {
-        return links.stream().filter(it -> it.getTags().stream().anyMatch(tag -> tag.getName().equals(tagName))).collect(Collectors.toSet());
+		return links.stream().filter(link -> link.hasTagName(tagName)).collect(Collectors.toSet());
 	}
 
 	public Set<Link> getByUser(Username username) {
-        return links.stream().filter(it -> it.getCreator().equals(username)).collect(Collectors.toSet());
+		return links.stream().filter(link -> link.wasCreatedBy(username)).collect(Collectors.toSet());
+	}
+
+	public List<Link> groupByHost() {
+		var input = new ArrayList<>(links.stream().toList());
+		var result = new ArrayList<Link>();
+
+		boolean changed = false;
+		while (!input.isEmpty()) {
+			input.removeAll(result);
+			changed = false;
+			for (Link link : input) {
+				if (result.stream().anyMatch(resultLink -> resultLink.getUrl().hostEquals(link.getUrl()))) {
+					result.add(link);
+					changed = true;
+				}
+			}
+			if (!changed && !input.isEmpty()) {
+				result.add(input.get(0));
+			}
+		}
+		return result;
 	}
 }

3-Domain/src/main/java/link/LinkUrl.java

@@ -22,6 +22,25 @@ public class LinkUrl {
 		return url;
 	}
 
+	public boolean hostEquals(LinkUrl other) {
+		return this.url.getHost().equals(other.getUrl().getHost());
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (o == null || getClass() != o.getClass()) return false;
+
+		LinkUrl linkUrl = (LinkUrl) o;
+
+		return url != null ? url.toString().equals(linkUrl.url.toString()) : linkUrl.url == null;
+	}
+
+	@Override
+	public int hashCode() {
+		return url != null ? url.toString().hashCode() : 0;
+	}
+
 	@Override
 	public String toString() {
 		return url.toString();