finish http handling, start persistence work

build.gradle.kts

@@ -34,6 +34,7 @@ application {
 
 dependencies {
   implementation("org.nanohttpd:nanohttpd:2.3.1")
+  implementation("redis.clients:jedis:3.3.0")
   implementation("io.vavr:vavr:1.0.0-alpha-3")
   testImplementation("junit", "junit", "4.12")
 }

src/main/java/nouritsu/Dao.java

@@ -1,18 +1,54 @@
 package nouritsu;
 
-import io.vavr.collection.List;
+import io.vavr.collection.HashSet;
 import io.vavr.control.Either;
-import nouritsu.types.Message;
+import nouritsu.types.Resp;
+import nouritsu.types.Section;
+import nouritsu.types.ShoppingItem;
+import nouritsu.types.Store;
+import redis.clients.jedis.Jedis;
+import redis.clients.jedis.JedisPool;
 
-import java.util.stream.Collectors;
+import java.util.function.Function;
 
 public class Dao {
-  public Either<Message, String> clearList(String id) {
-    return Either.right("Cleared list of user “%s“".formatted(id));
+  private final JedisPool pool;
+
+  Dao() {
+    pool = new JedisPool();
   }
 
-  public Either<Message, String> getList(String id) {
-    return Either.right(List.of("first", "second", "third")
-      .collect(Collectors.joining(",")));
+  private <T> T withRedis(Function<Jedis, T> f) {
+    try (var redis = pool.getResource()) {
+      return f.apply(redis);
+    }
+  }
+
+  public String clearList(String id) {
+    withRedis(redis -> redis.del(id));
+    // Just always return okay, even if we didn’t have data to begin with.
+    // Idempotency yay \o/
+    return "Cleared list of user “%s“".formatted(id);
+  }
+
+  public Either<Resp, HashSet<ShoppingItem>> getList(String id) {
+    return withRedis(redis ->
+      redis.exists(id)
+        ? Either.right(HashSet.ofAll(redis.smembers(id)).map(s -> new ShoppingItem(s, Section.CANS)))
+        : Either.left(Resp.NOT_FOUND.apply("No list found for user “%s”".formatted(id)))
+    );
+  }
+
+  public Either<Resp, String> addToList(String id, String item) {
+    return Either.right("Added “%s“ to list of user “%s”".formatted(item, id));
+  }
+
+  public String addItem(ShoppingItem item) {
+    return "Registered new item “%s” under the section “%s”"
+      .formatted(item.name(), item.section().name().toLowerCase());
+  }
+
+  public Either<Resp, String> addStore(Store store) {
+    return Either.right("Registered new store “%s” with the sections [%s]".formatted(store.name(), store.sections()));
   }
 }

src/main/java/nouritsu/Nouritsu.java

@@ -2,15 +2,18 @@ package nouritsu;
 
 import fi.iki.elonen.NanoHTTPD;
 import fi.iki.elonen.NanoHTTPD.Response.Status;
+import io.vavr.Tuple;
 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 nouritsu.types.Resp;
+import nouritsu.types.ShoppingItem;
+import nouritsu.types.Store;
 
 import java.io.IOException;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 
 public class Nouritsu extends NanoHTTPD {
@@ -26,6 +29,7 @@ public class Nouritsu extends NanoHTTPD {
   public Response serve(IHTTPSession session) {
     return Try.of(() -> processRequest(session, dao))
       .fold(
+        // This won’t be exposed to the outside world, so returning the error message is fine
         err -> newFixedLengthResponse(Status.INTERNAL_ERROR, MIME_PLAINTEXT, err.getMessage()),
         response -> newFixedLengthResponse(response.status(), MIME_PLAINTEXT, response.text())
       );
@@ -35,61 +39,81 @@ public class Nouritsu extends NanoHTTPD {
     Valid endpoints are (not case sensitive):
     /addStore/?name=storeName&sections=first,second,third
     /addItem/?name=itemName&category=itemCategory
-    /addToList/?user=userId&itemName
+    /addToList/?user=userId&item=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);
+  private static Resp processRequest(IHTTPSession session, Dao dao) {
+    // Type inference can’t handle this :feelsBadMan:
+    BiFunction<Map<String, String>, Dao, Resp> handler =
+      switch (session.getUri().replaceAll("/", "").toLowerCase()) {
+        case "addstore" -> Nouritsu::addStore;
+        case "additem" -> Nouritsu::addItem;
+        case "addtolist" -> Nouritsu::addToList;
+        case "getlist" -> Nouritsu::getList;
+        case "clearlist" -> Nouritsu::clearList;
+        default -> (_1, _2) -> Resp.NOT_FOUND.apply(HELP);
       };
+    return handler.apply(extractParams(session), dao);
   }
 
-  // Repack the parameters into vavr collections.
-  private static Map<String, List<String>> extractParams(IHTTPSession session) {
+  // Repack the parameters into a vavr Map<Key, Head(Value)>.
+  // Each parameter should only occur once per request.
+  private static Map<String, String> extractParams(IHTTPSession session) {
     return session.getParameters()
       .entrySet()
       .stream()
-      .map(e -> new Tuple2<>(e.getKey(), List.ofAll(e.getValue())))
-      .collect(HashMap.collector());
+      .map(Tuple::fromEntry)
+      .collect(HashMap.collector())
+      // guaranteed to be non-empty
+      .mapValues(list -> list.get(0));
   }
 
-  private static Message clearList(Map<String, List<String>> params, Dao dao) {
+  private static Resp clearList(Map<String, 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);
+      .map(dao::clearList)
+      .fold(Function.identity(), Resp.CREATED);
   }
 
-  private static Message getList(Map<String, List<String>> params, Dao dao) {
+  private static Resp getList(Map<String, 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);
+      .map(shoppingItems -> shoppingItems.mkString(","))
+      .fold(Function.identity(), Resp.OK);
   }
 
-  private static Message addToList(Map<String, List<String>> params, Dao dao) {
-    return new Message("", Status.NOT_IMPLEMENTED);
+  private static Resp addToList(Map<String, String> params, Dao dao) {
+    return getAsTuple(params, "user", "item")
+      // This is where Kotlin-like destructuring would be really nice to have:
+      // flatMap(id, item -> ...)
+      .flatMap(t -> dao.addToList(t._1, t._2))
+      .fold(Function.identity(), Resp.CREATED);
   }
 
-  private static Message addItem(Map<String, List<String>> params, Dao dao) {
-    return new Message("", Status.NOT_IMPLEMENTED);
+  private static Resp addItem(Map<String, String> params, Dao dao) {
+    return getAsTuple(params, "name", "category")
+      .flatMap(t -> ShoppingItem.tryParse(t._1, t._2))
+      .map(dao::addItem)
+      .fold(Function.identity(), Resp.CREATED);
   }
 
-  private static Message addStore(Map<String, List<String>> params, Dao dao) {
-    return new Message("", Status.NOT_IMPLEMENTED);
+  private static Resp addStore(Map<String, String> params, Dao dao) {
+    return getAsTuple(params, "name", "categories")
+      .flatMap(t -> Store.tryParse(t._1, t._2))
+      .flatMap(dao::addStore)
+      .fold(Function.identity(), Resp.CREATED);
   }
 
-  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));
+  private static Either<Resp, String> getFromParams(Map<String, String> params, String key) {
+    return params.get(key).toEither(Resp.NOT_FOUND.apply("Parameter “%s” not found".formatted(key)));
+  }
+
+  // Get k1 and k2 as a tuple in Either.Right or Either.Left if k1 or k2 is/are not in the map.
+  private static Either<Resp, Tuple2<String, String>> getAsTuple(Map<String, String> params, String k1, String k2) {
+    return getFromParams(params, k1)
+      .map(Tuple::of)
+      .flatMap(name -> getFromParams(params, k2).map(name::append));
   }
 
   public static void main(String[] args) {

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

@@ -1,12 +0,0 @@
-package nouritsu.types;
-
-public enum Category {
-    CANS,
-    FRUITS,
-    VEGETABLES,
-    PASTA,
-    RICE,
-    MEAT,
-    DAIRY,
-    HYGIENE,
-}

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

@@ -1,11 +0,0 @@
-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/Resp.java

@@ -0,0 +1,11 @@
+package nouritsu.types;
+
+import fi.iki.elonen.NanoHTTPD.Response.Status;
+import io.vavr.Function1;
+
+public record Resp(String text, Status status) {
+  public static Function1<String, Resp> OK = Function1.of(s -> new Resp(s, Status.OK));
+  public static Function1<String, Resp> BAD_REQUEST = Function1.of(s -> new Resp(s, Status.BAD_REQUEST));
+  public static Function1<String, Resp> CREATED = Function1.of(s -> new Resp(s, Status.CREATED));
+  public static Function1<String, Resp> NOT_FOUND = Function1.of(s -> new Resp(s, Status.NOT_FOUND));
+}

src/main/java/nouritsu/types/Section.java

@@ -0,0 +1,21 @@
+package nouritsu.types;
+
+import io.vavr.collection.Stream;
+import io.vavr.control.Either;
+
+public enum Section {
+  CANS,
+  FRUITS,
+  VEGETABLES,
+  PASTA,
+  RICE,
+  MEAT,
+  DAIRY,
+  HYGIENE;
+
+  public static Either<Resp, Section> tryParse(String catName) {
+    return Stream.of(Section.values())
+      .find(c -> c.name().equalsIgnoreCase(catName))
+      .toEither(Resp.BAD_REQUEST.apply("Category “%s” not found".formatted(catName)));
+  }
+}

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

@@ -1,4 +1,9 @@
 package nouritsu.types;
 
-public record ShoppingItem(String name, Category category) {
+import io.vavr.control.Either;
+
+public record ShoppingItem(String name, Section section) {
+  public static Either<Resp, ShoppingItem> tryParse(String name, String category) {
+    return Section.tryParse(category).map(c -> new ShoppingItem(name, c));
+  }
 }

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

@@ -1,9 +1,16 @@
 package nouritsu.types;
 
-import java.util.List;
+import io.vavr.collection.List;
+import io.vavr.collection.Seq;
+import io.vavr.control.Either;
 
 /**
  * A store with an ordered list of sections from entrance to exit.
  */
-public record Store(String name, List<Category> sections) {
+public record Store(String name, Seq<Section>sections) {
+  public static Either<Resp, Store> tryParse(String name, String sections) {
+    return Either.traverse(List.of(sections.split(",")), Section::tryParse)
+      .mapLeft(errors -> Resp.BAD_REQUEST.apply(errors.mkString("\n")))
+      .map(secs -> new Store(name, secs));
+  }
 }