.

build.gradle.kts

@@ -29,8 +29,8 @@ subprojects {
         // https://mvnrepository.com/artifact/com.google.guava/guava
         implementation("com.google.guava:guava:33.5.0-jre")
 
-        // https://www.mongodb.com/docs/drivers/java/sync/current/get-started/
-        implementation(platform("org.mongodb:mongodb-driver-bom:5.6.3"))
-        implementation("org.mongodb:mongodb-driver-sync")
+        // https://www.mongodb.com/docs/languages/java/reactive-streams-driver/current/get-started/download-and-install/
+        implementation(platform("org.mongodb:mongodb-driver-bom:5.6.1"))
+        implementation("org.mongodb:mongodb-driver-reactivestreams")
     }
 }

core-api/src/main/java/de/kentoj/scrow/services/EconomyService.java

@@ -11,9 +11,8 @@ public interface EconomyService {
 
     /**
      * @param playerId uuid of player
-     * @return new coins balance
      */
-    Mono<@NotNull Integer> depositCoins(UUID playerId, int amount);
+    Mono<@NotNull Void> depositCoins(UUID playerId, int amount);
 
     /**
      * @param playerId uuid of player

core-impl/src/main/java/de/kentoj/scrow/economy/EconomyServiceImpl.java

@@ -1,4 +1,73 @@
 package de.kentoj.scrow.economy;
 
-public class EconomyServiceImpl {
+import com.google.common.base.Preconditions;
+import com.mongodb.client.model.Filters;
+import com.mongodb.client.model.UpdateOptions;
+import com.mongodb.client.model.Updates;
+import com.mongodb.reactivestreams.client.MongoCollection;
+import com.mongodb.reactivestreams.client.MongoDatabase;
+import de.kentoj.scrow.services.EconomyService;
+import org.bson.Document;
+import org.jetbrains.annotations.NotNull;
+import reactor.core.publisher.Mono;
+
+import java.util.UUID;
+
+public class EconomyServiceImpl implements EconomyService {
+
+    private static final String COLLECTION_NAME = "economy";
+    private final @NotNull MongoDatabase database;
+
+    public EconomyServiceImpl(MongoDatabase database) {
+        this.database = database;
+        Mono.from(database.createCollection(COLLECTION_NAME)).block();
+    }
+
+    @Override
+    public Mono<@NotNull Integer> getCoins(UUID playerId) {
+        return Mono.from(
+                getCollection().find(Filters.eq("_id", playerId)).first()
+        ).map(result -> result.getInteger("coins")).defaultIfEmpty(0);
+    }
+
+    @Override
+    public Mono<@NotNull Void> setCoins(UUID playerId, int amount) {
+        Preconditions.checkArgument(amount >= 0, "amount can not be negative");
+
+        return Mono.from(
+                getCollection().updateOne(
+                        Filters.eq("_id", playerId),
+                        Updates.set("coins", amount),
+                        new UpdateOptions().upsert(true)
+                )
+        ).then();
+    }
+
+    @Override
+    public Mono<@NotNull Void> depositCoins(UUID playerId, int amount) {
+        Preconditions.checkArgument(amount >= 0, "amount can not be negative");
+
+        return Mono.from(getCollection().updateOne(
+                Filters.eq("_id", playerId),
+                Updates.inc("coins", amount),
+                new UpdateOptions().upsert(true)
+        )).then();
+    }
+
+    @Override
+    public Mono<@NotNull Boolean> tryWithdrawCoins(UUID playerId, int amount) {
+        Preconditions.checkArgument(amount >= 0, "amount can not be negative");
+
+        return Mono.from(getCollection().updateOne(
+                Filters.and(
+                        Filters.eq("_id", playerId),
+                        Filters.gte("coins", amount)
+                ),
+                Updates.inc("coins", -1 * amount)
+        )).map(result -> result.getModifiedCount() > 0);
+    }
+
+    private MongoCollection<Document> getCollection() {
+        return database.getCollection(COLLECTION_NAME);
+    }
 }

core-impl/src/main/java/de/kentoj/scrow/economy/Main.java

@@ -1,8 +1,28 @@
 package de.kentoj.scrow.economy;
 
+import de.kentoj.scrow.services.EconomyService;
+import reactor.core.publisher.Mono;
+
+import java.util.UUID;
+
 public class Main {
     public static void main(String[] args) {
-        var a = new MongoDbHelper();
-        a.close();
+        var con = new MongoDbHelper();
+
+        var playerId = UUID.randomUUID();
+        EconomyService economyService = new EconomyServiceImpl(con.getDatabase());
+        Mono.when(
+                        economyService.setCoins(playerId, 120),
+                        economyService.depositCoins(playerId, 100)
+                )
+                .then(economyService.tryWithdrawCoins(playerId, 300))
+                .doOnNext(a -> System.out.println("withdraw 1 success " + a))
+                .then(economyService.tryWithdrawCoins(playerId, 50))
+                .doOnNext(a -> System.out.println("withdraw 2 success " + a))
+                .then(economyService.getCoins(playerId))
+                .doOnNext(a -> System.out.println("coins: " + a))
+                .block();
+
+        con.close();
     }
 }

core-impl/src/main/java/de/kentoj/scrow/economy/MongoDbHelper.java

@@ -1,9 +1,12 @@
 package de.kentoj.scrow.economy;
 
-import com.mongodb.client.MongoClient;
-import com.mongodb.client.MongoClients;
-import com.mongodb.client.MongoDatabase;
+import com.mongodb.ConnectionString;
+import com.mongodb.MongoClientSettings;
+import com.mongodb.reactivestreams.client.MongoClient;
+import com.mongodb.reactivestreams.client.MongoClients;
+import com.mongodb.reactivestreams.client.MongoDatabase;
 import lombok.Getter;
+import org.bson.UuidRepresentation;
 
 import java.io.Closeable;
 
@@ -14,7 +17,11 @@ public class MongoDbHelper implements Closeable {
     private final MongoDatabase database;
 
     public MongoDbHelper() {
-        con = MongoClients.create("mongodb://:@localhost:27017/db?ssl=false");
+        var settings = MongoClientSettings.builder()
+                .applyConnectionString(new ConnectionString("mongodb://localhost:27017/scrow?ssl=false"))
+                .uuidRepresentation(UuidRepresentation.STANDARD)
+                .build();
+        con = MongoClients.create(settings);
         database = con.getDatabase("scrow");
     }