implement the ProxyManager

untested

core/build.gradle.kts

@@ -1,6 +1,7 @@
 plugins {
     alias(libs.plugins.blossom)
     alias(libs.plugins.indragit)
+    alias(libs.plugins.protobuf)
 }
 
 description = "Core functions for valiobungee"
@@ -20,3 +21,24 @@ java {
     withJavadocJar()
     withSourcesJar()
 }
+
+dependencies {
+    api(project(":valiobungee-api"))
+    api(libs.protobuf)
+    api(libs.caffeine)
+    api(libs.slf4j)
+
+    testImplementation(libs.testing.juipter)
+    testImplementation(libs.testing.slf4j.simple)
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+protobuf {
+    protoc {
+        artifact = libs.protoc.get().toString()
+    }
+}
+

core/src/main/java/net/limework/valiobungee/core/ProxyManager.java

@@ -0,0 +1,103 @@
+/*
+* Copyright (c) 2026-present ValioBungee contributors
+* All rights reserved. This program and the accompanying materials
+* are made available under the terms of the GNU GENERAL PUBLIC LICENSE Version 3
+* which accompanies this distribution, and is available at
+* https://www.gnu.org/licenses/gpl-3.0.txt
+*/
+package net.limework.valiobungee.core;
+
+import com.github.benmanes.caffeine.cache.Cache;
+import com.github.benmanes.caffeine.cache.Caffeine;
+import com.github.benmanes.caffeine.cache.RemovalCause;
+import com.github.benmanes.caffeine.cache.RemovalListener;
+import java.time.Duration;
+import java.util.UUID;
+import net.limework.valiobungee.core.proto.messages.*;
+import net.limework.valiobungee.core.util.logging.LogProviderFactory;
+import org.slf4j.Logger;
+
+/**
+ * This abstract class is responsible for proxy discovery and count online players as its cached
+ * locally Why abstract? Because it allows us to develop alternative implementation to use other
+ * software than valkey or redis
+ */
+public abstract class ProxyManager {
+
+  protected final UUID proxyManagerId = UUID.randomUUID();
+  protected final ValioBungeePlatform platform;
+
+  public ProxyManager(ValioBungeePlatform platform) {
+    this.platform = platform;
+  }
+
+  protected final Logger log = LogProviderFactory.get();
+
+  // proxy info class here stores the ProxyManager ID hence we use another cache for online players
+  // reason we use caffeine cache it allows us to auto remove entries without need for scheduled
+  // tasks in the proxies when a proxy disappears without sending death message
+  private final Cache<String, Heartbeat> heartbeats =
+      Caffeine.newBuilder()
+          .expireAfterWrite(Duration.ofSeconds(30))
+          .removalListener(
+              (RemovalListener<String, Heartbeat>)
+                  (key, value, cause) -> {
+                    if (cause == RemovalCause.EXPIRED) {
+                      assert value != null;
+                      log.warn("proxy {} has disconnected but did not send death message", value);
+                    }
+                  })
+          .build();
+
+  protected void handleProxyHeartBeat(Heartbeat payload) {
+    if (!this.heartbeats.asMap().containsKey(payload.getSender().getProxyId()))
+      log.info("Proxy {} has connected!", payload.getSender().getProxyId());
+    this.heartbeats.put(payload.getSender().getProxyId(), payload);
+  }
+
+  protected void handleProxyDeath(Death payload) {
+    this.heartbeats.invalidate(payload.getSender().getProxyId());
+    log.info("Proxy {} has disconnected", payload.getSender().getProxyId());
+  }
+
+  public int onlinePlayersCount() {
+    // reason we + local online players because our proxy is not inside it own heartbeat cache
+    return heartbeats.asMap().values().stream().mapToInt(Heartbeat::getOnlinePlayersCount).sum()
+        + platform.localOnlinePlayers();
+  }
+
+  public int onlinePlayersCount(String proxyId) {
+    if (proxyId.equals(this.platform.proxyId())) {
+      return platform.localOnlinePlayers();
+    } else {
+      if (!heartbeats.asMap().containsKey(proxyId)) return 0; // don't error?
+      return heartbeats.asMap().get(proxyId).getOnlinePlayersCount();
+    }
+  }
+
+  protected ProxyInfo createProxyInfo() {
+    return ProxyInfo.newBuilder()
+        .setProxyId(platform.proxyId())
+        .setProxyManagerId(this.proxyManagerId.toString())
+        .build();
+  }
+
+  protected Death createDeathPayload() {
+    return Death.newBuilder().setSender(createProxyInfo()).setReason(DeathReason.SHUTDOWN).build();
+  }
+
+  protected Heartbeat createHeartbeatPayload() {
+    return Heartbeat.newBuilder()
+        .setSender(createProxyInfo())
+        .setOnlinePlayersCount(platform.localOnlinePlayers())
+        .build();
+  }
+
+  protected abstract void publishDeathPayload();
+
+  protected abstract void publishHeartbeatPayload();
+
+  public abstract void init();
+
+  public abstract void close();
+}

core/src/main/java/net/limework/valiobungee/core/ValioBungeePlatform.java

@@ -0,0 +1,21 @@
+/*
+* Copyright (c) 2026-present ValioBungee contributors
+* All rights reserved. This program and the accompanying materials
+* are made available under the terms of the GNU GENERAL PUBLIC LICENSE Version 3
+* which accompanies this distribution, and is available at
+* https://www.gnu.org/licenses/gpl-3.0.txt
+*/
+package net.limework.valiobungee.core;
+
+public interface ValioBungeePlatform {
+
+  int localOnlinePlayers();
+
+  String platformProxyVendor();
+
+  String networkId();
+
+  String proxyId();
+
+  ProxyManager proxyManager();
+}

core/src/main/java/net/limework/valiobungee/core/api/impl/ImplNetworkProxy.java

@@ -0,0 +1,38 @@
+/*
+* Copyright (c) 2026-present ValioBungee contributors
+* All rights reserved. This program and the accompanying materials
+* are made available under the terms of the GNU GENERAL PUBLIC LICENSE Version 3
+* which accompanies this distribution, and is available at
+* https://www.gnu.org/licenses/gpl-3.0.txt
+*/
+package net.limework.valiobungee.core.api.impl;
+
+import net.limework.valiobungee.api.NetworkProxy;
+import net.limework.valiobungee.core.ValioBungeePlatform;
+
+public class ImplNetworkProxy implements NetworkProxy {
+
+  private final ValioBungeePlatform platform;
+
+  private final String proxyId;
+
+  public ImplNetworkProxy(ValioBungeePlatform platform, String proxyId) {
+    this.platform = platform;
+    this.proxyId = proxyId;
+  }
+
+  @Override
+  public String proxyId() {
+    return this.proxyId;
+  }
+
+  @Override
+  public int onlinePlayers() {
+    return this.platform.proxyManager().onlinePlayersCount(this.proxyId);
+  }
+
+  @Override
+  public boolean isMe() {
+    return this.platform.proxyId().equals(proxyId);
+  }
+}

core/src/main/java/net/limework/valiobungee/core/util/logging/LogProviderFactory.java

@@ -0,0 +1,24 @@
+/*
+* Copyright (c) 2026-present ValioBungee contributors
+* All rights reserved. This program and the accompanying materials
+* are made available under the terms of the GNU GENERAL PUBLIC LICENSE Version 3
+* which accompanies this distribution, and is available at
+* https://www.gnu.org/licenses/gpl-3.0.txt
+*/
+package net.limework.valiobungee.core.util.logging;
+
+import org.slf4j.Logger;
+
+public class LogProviderFactory {
+  private static Logger instance;
+
+  public static void register(Logger logger) {
+    if (instance != null) throw new IllegalStateException("Logger already registered");
+    instance = logger;
+  }
+
+  public static Logger get() {
+    if (instance == null) throw new IllegalStateException("No logger registered");
+    return instance;
+  }
+}

core/src/main/proto/message-protocol.proto

@@ -0,0 +1,28 @@
+syntax = "proto3";
+
+package net.limework.valiobungee.core.proto.messages;
+option java_multiple_files = true;
+
+message ProxyInfo {
+  string proxy_id = 1; // UNIQUE ID
+  string proxy_manager_id = 2; // ProxyManager id. changes every reboot, used to detect duplicate proxy names
+}
+
+// heartbeat ._.?
+
+message Heartbeat {
+  ProxyInfo sender = 1;
+  int32 online_players_count = 2;
+}
+
+// death
+enum DeathReason {
+  UNSPECIFIED = 0; // TESTING ONLY
+  RELOAD = 1; // plugin reload
+  SHUTDOWN = 2; // proxy shutdown
+}
+message Death {
+  ProxyInfo sender = 1; // proxy that died
+  DeathReason reason = 2;
+}
+