Implement mod implementation interface for use in downstream mods (#40)

This change will provide better expansion moving forward for the
downstream mod implementations, for now, the major addition is allowing
downstream mods to track if we are connected to Hypixel to prevent
sending plugin messages when we're not.

Author: ConnorLinfoot

src/main/java/net/hypixel/modapi/HypixelModAPI.java

@@ -16,11 +16,11 @@
 import net.hypixel.modapi.packet.impl.serverbound.ServerboundRegisterPacket;
 import net.hypixel.modapi.serializer.PacketSerializer;
 import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.function.Predicate;
 
 public class HypixelModAPI {
     private static final HypixelModAPI INSTANCE = new HypixelModAPI();
@@ -33,12 +33,12 @@ public static HypixelModAPI getInstance() {
     private final Map<String, Collection<RegisteredHandlerImpl<?>>> handlers = new ConcurrentHashMap<>();
     private final Set<String> subscribedEvents = ConcurrentHashMap.newKeySet();
     private Set<String> lastSubscribedEvents = Collections.emptySet();
-    private Predicate<HypixelPacket> packetSender = null;
+    @Nullable
+    private HypixelModAPIImplementation modImplementation;
 
     private HypixelModAPI() {
         registerHypixelPackets();
         registerEventPackets();
-        registerDefaultHandler();
     }
 
     private void registerHypixelPackets() {
@@ -77,8 +77,8 @@ private void registerDefaultHandler() {
     }
 
     private void sendRegisterPacket(boolean alwaysSendIfNotEmpty) {
-        if (packetSender == null) {
-            // Allow registering events before the mod has fully initialized
+        if (modImplementation == null || !modImplementation.isConnectedToHypixel()) {
+            // Allow registering events when not connected to Hypixel
             return;
         }
 
@@ -144,11 +144,18 @@ public void handleError(String identifier, ErrorReason reason) {
     }
 
     @ApiStatus.Internal
-    public void setPacketSender(Predicate<HypixelPacket> packetSender) {
-        if (this.packetSender != null) {
-            throw new IllegalArgumentException("Packet sender already set");
+    public void setModImplementation(HypixelModAPIImplementation modImplementation) {
+        if (this.modImplementation != null) {
+            throw new IllegalStateException("Mod implementation already set");
+        }
+
+        if (modImplementation == null) {
+            throw new NullPointerException("modImplementation cannot be null");
         }
-        this.packetSender = packetSender;
+
+        this.modImplementation = modImplementation;
+        this.modImplementation.onInit();
+        registerDefaultHandler();
     }
 
     /**
@@ -184,11 +191,11 @@ public void subscribeToEventPacket(Class<? extends EventPacket> packet) {
      * @return whether the packet was sent successfully
      */
     public boolean sendPacket(HypixelPacket packet) {
-        if (packetSender == null) {
-            throw new IllegalStateException("Packet sender not set");
+        if (modImplementation == null) {
+            throw new IllegalStateException("Mod implementation not set");
         }
 
-        return packetSender.test(packet);
+        return modImplementation.sendPacket(packet);
     }
 
     private static class RegisteredHandlerImpl<T extends ClientboundHypixelPacket> implements RegisteredHandler<T> {

src/main/java/net/hypixel/modapi/HypixelModAPIImplementation.java

@@ -0,0 +1,15 @@
+package net.hypixel.modapi;
+
+import net.hypixel.modapi.packet.HypixelPacket;
+import org.jetbrains.annotations.ApiStatus;
+
+@ApiStatus.Internal
+public interface HypixelModAPIImplementation {
+
+    void onInit();
+
+    boolean sendPacket(HypixelPacket packet);
+
+    boolean isConnectedToHypixel();
+
+}