Improve error handling to be more defined

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

@@ -1,5 +1,7 @@
 package net.hypixel.modapi;
 
+import net.hypixel.modapi.error.ErrorReason;
+import net.hypixel.modapi.error.ModAPIException;
 import net.hypixel.modapi.handler.ClientboundPacketHandler;
 import net.hypixel.modapi.packet.HypixelPacket;
 import net.hypixel.modapi.packet.HypixelPacketType;
@@ -36,8 +38,8 @@ public void handle(String identifier, PacketSerializer serializer) {
 
         // All responses contain a boolean of if the response is a success, if not then a string is included with the error message
         if (!serializer.readBoolean()) {
-            String errorMessage = serializer.readString();
-            throw new RuntimeException("Received error response for packet " + packetType + ": " + errorMessage);
+            ErrorReason reason = ErrorReason.getById(serializer.readVarInt());
+            throw new ModAPIException(packetType, reason);
         }
 
         HypixelPacket packet = packetType.getPacketFactory().apply(serializer);

src/main/java/net/hypixel/modapi/error/BuiltinErrorReason.java

@@ -0,0 +1,33 @@
+package net.hypixel.modapi.error;
+
+import java.util.Arrays;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public enum BuiltinErrorReason implements ErrorReason {
+    DISABLED(1),
+    INTERNAL_SERVER_ERROR(2),
+    RATE_LIMITED(3),
+    INVALID_PACKET_VERSION(4),
+    NO_LONGER_SUPPORTED(5),
+    ;
+
+    private static final Map<Integer, BuiltinErrorReason> BY_ID = Arrays.stream(values())
+            .collect(Collectors.toMap(BuiltinErrorReason::getId, Function.identity()));
+
+    static BuiltinErrorReason getById(int id) {
+        return BY_ID.get(id);
+    }
+
+    private final int id;
+
+    BuiltinErrorReason(int id) {
+        this.id = id;
+    }
+
+    @Override
+    public int getId() {
+        return id;
+    }
+}

src/main/java/net/hypixel/modapi/error/ErrorReason.java

@@ -0,0 +1,14 @@
+package net.hypixel.modapi.error;
+
+public interface ErrorReason {
+    int getId();
+
+    static ErrorReason getById(int id) {
+        BuiltinErrorReason reason = BuiltinErrorReason.getById(id);
+        if (reason != null) {
+            return reason;
+        }
+
+        return new UnknownErrorReason(id);
+    }
+}

src/main/java/net/hypixel/modapi/error/ModAPIException.java

@@ -0,0 +1,30 @@
+package net.hypixel.modapi.error;
+
+import net.hypixel.modapi.packet.HypixelPacketType;
+
+public class ModAPIException extends RuntimeException {
+    private final HypixelPacketType packetType;
+    private final ErrorReason reason;
+
+    public ModAPIException(HypixelPacketType packetType, ErrorReason reason) {
+        super(String.format("Received error response '%s' from packet '%s'", reason, packetType));
+        this.packetType = packetType;
+        this.reason = reason;
+    }
+
+    public HypixelPacketType getPacketType() {
+        return packetType;
+    }
+
+    public ErrorReason getReason() {
+        return reason;
+    }
+
+    @Override
+    public String toString() {
+        return "ModAPIException{" +
+                "packetType=" + packetType +
+                ", reason=" + reason +
+                "} " + super.toString();
+    }
+}

src/main/java/net/hypixel/modapi/error/UnknownErrorReason.java

@@ -0,0 +1,21 @@
+package net.hypixel.modapi.error;
+
+public class UnknownErrorReason implements ErrorReason {
+    private final int id;
+
+    UnknownErrorReason(int id) {
+        this.id = id;
+    }
+
+    @Override
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public String toString() {
+        return "UnknownErrorReason{" +
+                "id=" + id +
+                '}';
+    }
+}