Don't repeat validation in AvailableCommands

When deserializing an AvailableCommands packet, we do a few sanity checks to ensure the packet is valid. Some of this work was repeated for each cycle (notably the root) so we now check the children and any redirects are defined only once.

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/AvailableCommands.java

@@ -204,6 +204,7 @@ public class AvailableCommands implements MinecraftPacket {
     private final int redirectTo;
     private final @Nullable ArgumentBuilder<CommandSource, ?> args;
     private @MonotonicNonNull CommandNode<CommandSource> built;
+    private boolean validated;
 
     private WireNode(int idx, byte flags, int[] children, int redirectTo,
         @Nullable ArgumentBuilder<CommandSource, ?> args) {
@@ -212,10 +213,10 @@ public class AvailableCommands implements MinecraftPacket {
       this.children = children;
       this.redirectTo = redirectTo;
       this.args = args;
+      this.validated = false;
     }
 
-    boolean toNode(WireNode[] wireNodes) {
+    void validate(WireNode[] wireNodes) {
-      if (this.built == null) {
       // Ensure all children exist. Note that we delay checking if the node has been built yet;
       // that needs to come after this node is built.
       for (int child : children) {
@@ -224,6 +225,21 @@ public class AvailableCommands implements MinecraftPacket {
         }
       }
 
+      if (redirectTo != -1) {
+        if (redirectTo >= wireNodes.length) {
+          throw new IllegalStateException("Node points to non-existent index " + redirectTo);
+        }
+      }
+
+      this.validated = true;
+    }
+
+    boolean toNode(WireNode[] wireNodes) {
+      if (!this.validated) {
+        this.validate(wireNodes);
+      }
+
+      if (this.built == null) {
         int type = flags & FLAG_NODE_TYPE;
         if (type == NODE_TYPE_ROOT) {
           this.built = new RootCommandNode<>();
@@ -234,10 +250,6 @@ public class AvailableCommands implements MinecraftPacket {
 
           // Add any redirects
           if (redirectTo != -1) {
-            if (redirectTo >= wireNodes.length) {
-              throw new IllegalStateException("Node points to non-existent index " + redirectTo);
-            }
-
             WireNode redirect = wireNodes[redirectTo];
             if (redirect.built != null) {
               args.redirect(redirect.built);