Day 16: Withstanding the change of time.

README.md

@@ -61,6 +61,7 @@ Here are the different challenges :
 - [Day 13: Find a way to eliminate the irrelevant, and amplify the essentials of those tests.](exercise/day13/docs/challenge.md)
 - [Day 14: Do not use exceptions anymore.](exercise/day14/docs/challenge.md)
 - [Day 15: Put a code under tests.](exercise/day15/docs/challenge.md)
+- [Day 16: Make this code immutable.](exercise/day16/docs/challenge.md)
 
 ### Solutions
 A solution proposal will be published here every day during the `Advent Of Craft` containing `the code` and a `step by step` guide.

exercise/day16/docs/challenge.md

@@ -0,0 +1,25 @@
+## Day 16: Withstanding the change of time.
+
+Today, you are passing through a agitated sea.
+A tornado is raging not far from your area, and you have to change course.
+
+Today's exercise is about sustaining code.
+A code that is robust and that will weather changes.
+
+There are different avenues for code improvement:
+
+- We looked at breaking conditions, better naming, avoiding complexity
+  and even dependency check.
+
+But we are not talking about these refactoring steps.
+No, today we focus our effort into a simple question:
+
+_Is my code better mutable or immutable?_
+
+> **Day 16: Make this code immutable.**
+
+May you be protected on your crafting journey!
+
+- <u>💡HINT:</u> Code from usage for this one.
+
+![snippet of the day](snippet.png)

exercise/day16/pom.xml

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>com.advent-of-craft</groupId>
+        <artifactId>advent-of-craft2023</artifactId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>blog-part3</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <properties>
+        <instancio-junit.version>3.0.0</instancio-junit.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.instancio</groupId>
+            <artifactId>instancio-junit</artifactId>
+            <version>${instancio-junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

exercise/day16/src/main/java/blog/Article.java

@@ -0,0 +1,37 @@
+package blog;
+
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.List;
+
+public class Article {
+    private final String name;
+    private final String content;
+    private final ArrayList<Comment> comments;
+
+    public Article(String name, String content) {
+        this.name = name;
+        this.content = content;
+        this.comments = new ArrayList<>();
+    }
+
+    private void addComment(
+            String text,
+            String author,
+            LocalDate creationDate) throws CommentAlreadyExistException {
+        var comment = new Comment(text, author, creationDate);
+
+        if (comments.contains(comment)) {
+            throw new CommentAlreadyExistException();
+        } else comments.add(comment);
+    }
+
+    public void addComment(String text, String author) throws CommentAlreadyExistException {
+        addComment(text, author, LocalDate.now());
+    }
+
+    public List<Comment> getComments() {
+        return comments;
+    }
+}
+

exercise/day16/src/main/java/blog/Comment.java

@@ -0,0 +1,6 @@
+package blog;
+
+import java.time.LocalDate;
+
+public record Comment(String text, String author, LocalDate creationDate) {
+}

exercise/day16/src/main/java/blog/CommentAlreadyExistException.java

@@ -0,0 +1,4 @@
+package blog;
+
+public class CommentAlreadyExistException extends Exception {
+}

exercise/day16/src/test/java/blog/ArticleBuilder.java

@@ -0,0 +1,34 @@
+package blog;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class ArticleBuilder {
+    public static final String AUTHOR = "Pablo Escobar";
+    public static final String COMMENT_TEXT = "Amazing article !!!";
+    private final HashMap<String, String> comments;
+
+    public ArticleBuilder() {
+        comments = new HashMap<>();
+    }
+
+    public static ArticleBuilder anArticle() {
+        return new ArticleBuilder();
+    }
+
+    public ArticleBuilder commented() {
+        this.comments.put(COMMENT_TEXT, AUTHOR);
+        return this;
+    }
+
+    public Article build() throws CommentAlreadyExistException {
+        var article = new Article(
+                "Lorem Ipsum",
+                "consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore"
+        );
+        for (Map.Entry<String, String> comment : comments.entrySet()) {
+            article.addComment(comment.getKey(), comment.getValue());
+        }
+        return article;
+    }
+}

exercise/day16/src/test/java/blog/ArticleTests.java

@@ -0,0 +1,73 @@
+package blog;
+
+import org.assertj.core.api.ThrowingConsumer;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+import java.util.function.Function;
+
+import static blog.ArticleBuilder.*;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.instancio.Instancio.create;
+
+class ArticleTests {
+    private Article article;
+
+    @Test
+    void should_add_comment_in_an_article() throws CommentAlreadyExistException {
+        when(article -> article.addComment(COMMENT_TEXT, AUTHOR));
+        then(article -> {
+            assertThat(article.getComments()).hasSize(1);
+            assertComment(article.getComments().get(0), COMMENT_TEXT, AUTHOR);
+        });
+    }
+
+    @Test
+    void should_add_comment_in_an_article_containing_already_a_comment() throws Throwable {
+        final var newComment = create(String.class);
+        final var newAuthor = create(String.class);
+
+        when(ArticleBuilder::commented, article -> article.addComment(newComment, newAuthor));
+        then(article -> {
+            assertThat(article.getComments()).hasSize(2);
+            assertComment(article.getComments().getLast(), newComment, newAuthor);
+        });
+    }
+
+    @Nested
+    class Fail {
+        @Test
+        void when__adding_an_existing_comment() throws CommentAlreadyExistException {
+            var article = anArticle()
+                    .commented()
+                    .build();
+
+            assertThatThrownBy(() -> {
+                article.addComment(article.getComments().get(0).text(), article.getComments().get(0).author());
+            }).isInstanceOf(CommentAlreadyExistException.class);
+        }
+    }
+
+    private static void assertComment(Comment comment, String commentText, String author) {
+        assertThat(comment.text()).isEqualTo(commentText);
+        assertThat(comment.author()).isEqualTo(author);
+    }
+
+    private void when(ArticleBuilder articleBuilder, ThrowingConsumer<Article> act) throws CommentAlreadyExistException {
+        article = articleBuilder.build();
+        act.accept(article);
+    }
+
+    private void when(ThrowingConsumer<Article> act) throws CommentAlreadyExistException {
+        when(anArticle(), act);
+    }
+
+    private void when(Function<ArticleBuilder, ArticleBuilder> options, ThrowingConsumer<Article> act) throws Throwable {
+        when(options.apply(anArticle()), act);
+    }
+
+    private void then(ThrowingConsumer<Article> act) {
+        act.accept(article);
+    }
+}

exercise/pom.xml

@@ -24,6 +24,7 @@
 		<module>day13</module>
 		<module>day14</module>
 		<module>day15</module>
+		<module>day16</module>
     </modules>
 
     <properties>