initial commit

.gitignore

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+build/
+.gradle/

README.md

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+# 能率
+I’m trying to prove a point by implementing something in Java.
+More details will follow on [my blog](https://ruru.moe).

build.gradle.kts

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+plugins {
+  java
+  application
+}
+
+group = "moe.kageru"
+version = "0.1.0"
+
+repositories {
+  mavenCentral()
+}
+
+java {
+  sourceCompatibility = JavaVersion.VERSION_15
+  targetCompatibility = JavaVersion.VERSION_15
+}
+
+tasks.withType<JavaCompile> {
+  options.compilerArgs.add("--enable-preview")
+}
+
+tasks.run {
+}
+
+tasks.test {
+  useJUnitPlatform()
+  jvmArgs("--enable-preview")
+}
+
+application {
+  mainClass.set("nouritsu.Nouritsu")
+  applicationDefaultJvmArgs = listOf("--enable-preview")
+}
+
+dependencies {
+  implementation("org.nanohttpd:nanohttpd:2.3.1")
+  implementation("io.vavr:vavr:1.0.0-alpha-3")
+  testImplementation("junit", "junit", "4.12")
+}

settings.gradle.kts

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+rootProject.name = "nouritsu"
+

src/main/java/nouritsu/Dao.java

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+package nouritsu;
+
+import io.vavr.collection.List;
+import io.vavr.control.Either;
+import nouritsu.types.Message;
+
+import java.util.stream.Collectors;
+
+public class Dao {
+  public Either<Message, String> clearList(String id) {
+    return Either.right("Cleared list of user “%s“".formatted(id));
+  }
+
+  public Either<Message, String> getList(String id) {
+    return Either.right(List.of("first", "second", "third")
+      .collect(Collectors.joining(",")));
+  }
+}

src/main/java/nouritsu/Nouritsu.java

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+package nouritsu;
+
+import fi.iki.elonen.NanoHTTPD;
+import fi.iki.elonen.NanoHTTPD.Response.Status;
+import io.vavr.Tuple2;
+import io.vavr.collection.HashMap;
+import io.vavr.collection.List;
+import io.vavr.collection.Map;
+import io.vavr.control.Either;
+import io.vavr.control.Try;
+import nouritsu.types.Message;
+
+import java.io.IOException;
+import java.util.function.Function;
+
+public class Nouritsu extends NanoHTTPD {
+  private final Dao dao;
+
+  public Nouritsu(int port, Dao dao) throws IOException {
+    super(port);
+    start(10_000, false);
+    this.dao = dao;
+  }
+
+  @Override
+  public Response serve(IHTTPSession session) {
+    return Try.of(() -> processRequest(session, dao))
+      .fold(
+        err -> newFixedLengthResponse(Status.INTERNAL_ERROR, MIME_PLAINTEXT, err.getMessage()),
+        response -> newFixedLengthResponse(response.status(), MIME_PLAINTEXT, response.text())
+      );
+  }
+
+  private static final String HELP = """
+    Valid endpoints are (not case sensitive):
+    /addStore/?name=storeName&sections=first,second,third
+    /addItem/?name=itemName&category=itemCategory
+    /addToList/?user=userId&itemName
+    /getList/?user=userId&store=optionalStoreName
+    /clearList/?user=userId
+    """;
+
+  private static Message processRequest(IHTTPSession session, Dao dao) {
+    var params = extractParams(session);
+    return switch (session.getUri().replaceAll("/", "").toLowerCase()) {
+      case "", "index.html" -> new Message(HELP, Status.OK);
+      case "addstore" -> addStore(params, dao);
+      case "additem" -> addItem(params, dao);
+      case "addtolist" -> addToList(params, dao);
+      case "getlist" -> getList(params, dao);
+      case "clearlist" -> clearList(params, dao);
+      default -> new Message(HELP, Status.NOT_FOUND);
+    };
+  }
+
+  // Repack the parameters into vavr collections.
+  private static Map<String, List<String>> extractParams(IHTTPSession session) {
+    return session.getParameters()
+      .entrySet()
+      .stream()
+      .map(e -> new Tuple2<>(e.getKey(), List.ofAll(e.getValue())))
+      .collect(HashMap.collector());
+  }
+
+  private static Message clearList(Map<String, List<String>> params, Dao dao) {
+    return getFromParams(params, "user")
+      .map(List::head) // save, the list can’t be empty
+      .flatMap(dao::clearList)
+      .fold(Function.identity(), Message.OK);
+  }
+
+  private static Message getList(Map<String, List<String>> params, Dao dao) {
+    return getFromParams(params, "user")
+      .map(List::head) // save, the list can’t be empty
+      .flatMap(dao::getList)
+      .fold(Function.identity(), Message.OK);
+  }
+
+  private static Message addToList(Map<String, List<String>> params, Dao dao) {
+    return new Message("", Status.NOT_IMPLEMENTED);
+  }
+
+  private static Message addItem(Map<String, List<String>> params, Dao dao) {
+    return new Message("", Status.NOT_IMPLEMENTED);
+  }
+
+  private static Message addStore(Map<String, List<String>> params, Dao dao) {
+    return new Message("", Status.NOT_IMPLEMENTED);
+  }
+
+  private static Either<Message, List<String>> getFromParams(Map<String, List<String>> params, String key) {
+    return params.get(key).toEither(new Message("Parameter “%s” not found".formatted(key), Status.NOT_FOUND));
+  }
+
+  public static void main(String[] args) {
+    try {
+      new Nouritsu(14523, new Dao());
+    } catch (IOException e) {
+      e.printStackTrace();
+    }
+  }
+}

src/main/java/nouritsu/types/Category.java

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+package nouritsu.types;
+
+public enum Category {
+    CANS,
+    FRUITS,
+    VEGETABLES,
+    PASTA,
+    RICE,
+    MEAT,
+    DAIRY,
+    HYGIENE,
+}

src/main/java/nouritsu/types/Message.java

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+package nouritsu.types;
+
+import fi.iki.elonen.NanoHTTPD.Response.Status;
+import io.vavr.Function1;
+
+public record Message(String text, Status status) {
+  public static Function1<String, Message> OK = Function1.of(s -> new Message(s, Status.OK));
+  public static Function1<String, Message> BAD_REQUEST = Function1.of(s -> new Message(s, Status.BAD_REQUEST));
+  public static Function1<String, Message> CREATED = Function1.of(s -> new Message(s, Status.CREATED));
+  public static Function1<String, Message> NOT_FOUND = Function1.of(s -> new Message(s, Status.NOT_FOUND));
+}

src/main/java/nouritsu/types/ShoppingItem.java

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+package nouritsu.types;
+
+public record ShoppingItem(String name, Category category) {
+}

src/main/java/nouritsu/types/Store.java

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+package nouritsu.types;
+
+import java.util.List;
+
+/**
+ * A store with an ordered list of sections from entrance to exit.
+ */
+public record Store(String name, List<Category> sections) {
+}