Add ability tree composite implementation (#44)

Author: mperor

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/composite/Ability.java

@@ -0,0 +1,17 @@
+package pl.mperor.lab.java.design.pattern.structural.composite;
+
+public interface Ability {
+
+    String name();
+
+    int value();
+
+    static Ability of(String name, int value) {
+        return new SimpleAbility(name, value);
+    }
+
+    static Ability of(String name, Ability... abilities) {
+        return new ComplexAbility(name, abilities);
+    }
+
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/composite/AbilityUtils.java

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+package pl.mperor.lab.java.design.pattern.structural.composite;
+
+import java.util.stream.Collectors;
+
+public class AbilityUtils {
+
+    private AbilityUtils() {
+    }
+
+    public static void printAbilityTree(Ability root) {
+        System.out.println(printAbilityTree(root, 0));
+    }
+
+    private static String printAbilityTree(Ability ability, int level) {
+        var nested = "";
+        if (ability instanceof ComplexAbility ca) {
+            nested = ca.abilities().stream()
+                    .map(a -> printAbilityTree(a, level + 1))
+                    .collect(Collectors.joining());
+        }
+
+        return "%s%s (%d)%n%s".formatted(" ".repeat(level), ability.name(), ability.value(), nested);
+    }
+
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/composite/ComplexAbility.java

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+package pl.mperor.lab.java.design.pattern.structural.composite;
+
+import java.util.Arrays;
+import java.util.List;
+
+public record ComplexAbility(String name, List<Ability> abilities) implements Ability {
+
+    public ComplexAbility(String name, Ability... abilities) {
+        this(name, Arrays.asList(abilities));
+    }
+
+    @Override
+    public int value() {
+        return (int) abilities.stream()
+                .mapToInt(Ability::value)
+                .average()
+                .orElse(0);
+    }
+
+}

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/structural/composite/SimpleAbility.java

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+package pl.mperor.lab.java.design.pattern.structural.composite;
+
+public record SimpleAbility(String name, int value) implements Ability {
+}

DesignPatterns/src/test/java/pl/mperor/lab/java/design/pattern/structural/composite/AbilityTreeCompositeTest.java

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+package pl.mperor.lab.java.design.pattern.structural.composite;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class AbilityTreeCompositeTest {
+
+    @Test
+    public void testCreateAbilityTree() {
+        var physicalHealth = Ability.of("Physical Health",
+                Ability.of("Fitness",
+                        Ability.of("Jogging", 20),
+                        Ability.of("Stretching", 40),
+                        Ability.of("Swimming", 60)
+                ),
+                Ability.of("Sleep", 50),
+                Ability.of("Nutrition", 30)
+        );
+        Assertions.assertEquals(40, physicalHealth.value());
+
+        var mentalHealth = Ability.of("Mental Health",
+                Ability.of("Stress Management", 50)
+        );
+        Assertions.assertEquals(50, mentalHealth.value());
+
+        var lifeAndHealth = Ability.of("Life and Health",
+                physicalHealth,
+                mentalHealth,
+                Ability.of("Social Skills", 30)
+        );
+        Assertions.assertEquals(40, lifeAndHealth.value());
+
+        AbilityUtils.printAbilityTree(lifeAndHealth);
+    }
+
+}