Exercise 1: Reviewing code

build-extra.gradle

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+dependencies {
+    implementation("com.google.code.gson:gson:2.13.2")
+}

src/main/java/App.java

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+public class App {
+    public static void main(String[] args) {
+        new Presenter(new LocalDatabaseModel(), new ConsoleView()).run();
+    }
+}

src/main/java/ConsoleView.java

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+import java.util.Scanner;
+
+public final class ConsoleView implements View {
+    private final Scanner scanner = new Scanner(System.in);
+
+    public void show(String text) {
+        // Prints `text` on the console
+        System.out.println(text);
+    }
+
+    public void run(Presenter presenter, String prompt) {
+        while (true) {
+            System.out.print(prompt);
+            String command = scanner.nextLine();
+            presenter.onInput(command);
+        }
+    }
+}

src/main/java/LocalDatabaseModel.java

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+import java.io.*;
+import java.util.*;
+import java.util.stream.*;
+import com.google.gson.*;
+
+public final class LocalDatabaseModel implements Model {
+    private final JsonObject root;
+
+    public LocalDatabaseModel() {
+        try(var reader = new InputStreamReader(Model.class.getResourceAsStream("/dsonames.json"))) {
+            root = JsonParser.parseReader(reader).getAsJsonObject();
+        } catch (IOException e) {
+            throw new IOError(e);
+        }
+    }
+
+    public List<String> names() {
+        var result = new ArrayList<String>();
+        for (var entry : root.entrySet()) {
+            var planet = entry.getValue().getAsJsonObject();
+            result.add(planet.get("name").getAsString());
+        }
+        return result;
+    }
+
+    public Map<String, String> translatedNames(String language) {
+        return root.entrySet().stream()
+                   .map(e -> e.getValue().getAsJsonObject())
+                   .filter(p -> p.has(language))
+                   .collect(Collectors.toMap(p -> p.get("name").getAsString(), p -> p.get(language).getAsString(), (a, b) -> a));
+    }
+}

src/main/java/Model.java

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+import java.util.*;
+
+public interface Model {
+    List<String> names();
+    Map<String, String> translatedNames(String language);
+}

src/main/java/Presenter.java

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+import java.util.*;
+import java.util.stream.*;
+
+public final class Presenter {
+    private final Model model;
+    private final View view;
+
+    public Presenter(Model model, View view) {
+       this.model = model;
+       this.view = view;
+    }
+
+    public void onInput(String command) {
+        if (command.equals("list")) {
+            showList(model.names());
+            return;
+        }
+
+        var parts = command.split(" ");
+        if (parts[0].equals("searcch")) {
+            showList(model.names().stream().filter(n -> n.contains(parts[0])).toList());
+            return;
+        }
+        if (parts[0].equals("translate")) {
+            var names = model.translatedNames(parts[1]).entrySet();
+            showList(names.stream().map(e -> e.getKey() + ": " + e.getValue()).toList());
+            return;
+        }
+
+        view.show("Unknown command");
+    }
+
+    public void run() {
+        view.show("Hi! This app gives you info on star groups.");
+        view.run(this, "Type 'list', 'search <name>', or 'translate <language>' (or Ctrl+C): ");
+    }
+
+    private void showList(List<String> list) {
+        view.show(list.stream().map(s -> "- " + s).collect(Collectors.joining("\n")));
+    }
+}

src/main/java/View.java

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+public interface View {
+    void show(String text);
+    void run(Presenter presenter, String prompt);
+}

src/test/java/Tests.java

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+import java.util.*;
+
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+
+final class ExampleTest {
+    @Test
+    void namesAreLoaded() {
+        var model = new LocalDatabaseModel();
+        var names = model.names();
+        assertThat(names, hasItems("Sextans Dwarf Spheroidal Galaxy"));
+    }
+
+    @Test
+    void translatedNamesAreLoaded() {
+        var model = new LocalDatabaseModel();
+        var names = model.translatedNames("fr");
+        assertThat(names, hasEntry(is("Sextans Dwarf Spheroidal Galaxy"), is("Galaxie naine sphéroïdale du Sextant")));
+    }
+
+    @Test
+    void presenterListTest() {
+        var view = new FakeView();
+        view.inputs.add("list");
+        var pres = new Presenter(new FakeModel(), view);
+        assertThat(view.outputs, empty());
+        pres.run();
+        assertThat(view.outputs, contains("Hi! This app gives you info on star groups.", "- X\n- Y\n- Z"));
+    }
+
+    @Test
+    void presenterTranslateTest() {
+        var view = new FakeView();
+        view.inputs.add("translate fr");
+        var pres = new Presenter(new FakeModel(), view);
+        assertThat(view.outputs.isEmpty(), is(true));
+        pres.run();
+        assertThat(view.outputs, contains("Hi! This app gives you info on star groups.", "- X: A\n- Y: fr\n- Z: C"));
+    }
+
+    private static final class FakeModel implements Model {
+        @Override
+        public List<String> names() {
+            return List.of("X", "Y", "Z");
+        }
+
+        @Override
+        public Map<String, String> translatedNames(String language) {
+            var result = new LinkedHashMap<String, String>();
+            result.put("X", "A");
+            result.put("Y", language);
+            result.put("Z", "C");
+            return result;
+        }
+    }
+
+    private static final class FakeView implements View {
+        public List<String> inputs = new ArrayList<>();
+        public List<String> outputs = new ArrayList<>();
+
+        @Override
+        public void show(String text) {
+            outputs.add(text);
+        }
+
+        @Override
+        public void run(Presenter presenter, String prompt) {
+            if (!inputs.isEmpty()) {
+                presenter.onInput(inputs.get(0));
+                inputs.remove(0);
+            }
+        }
+    }
+}