extend ability system to support dynamic slot counts, add skill tree validation, new prerequisites API, and extended mod commands

src/main/java/net/fretux/skillengine/api/SkillEngineAPI.java

@@ -115,10 +115,11 @@ public final class SkillEngineAPI {
         if (unlockPlan == null) return false;
         for (SkillNode plannedNode : unlockPlan) {
             data.unlockNode(plannedNode);
-            if (plannedNode.getCost() > 0) {
+            int cost = Math.max(0, plannedNode.getCost());
+            if (cost > 0) {
                 MinecraftForge.EVENT_BUS.post(new SkillPointsChangedEvent(
                         player,
-                        plannedNode.getCost(),
+                        cost,
                         SkillPointsChangedEvent.Reason.SPENT,
                         plannedNode.getId()
                 ));
@@ -131,9 +132,10 @@ public final class SkillEngineAPI {
         PlayerSkillData data = getPlayerData(player);
         SkillNode node = SkillNodeRegistry.get(id);
         if (data == null || node == null || !data.refundNode(id)) return false;
+        int refunded = Math.max(0, node.getCost());
         MinecraftForge.EVENT_BUS.post(new SkillPointsChangedEvent(
                 player,
-                node.getCost(),
+                refunded,
                 SkillPointsChangedEvent.Reason.REFUNDED,
                 id
         ));

src/main/java/net/fretux/skillengine/capability/PlayerSkillData.java

@@ -55,7 +55,7 @@ public class PlayerSkillData {
         if (node == null) return;
         if (unlockedNodes.add(node.getId())) {
             activeTags.addAll(node.getTags());
-            skillPoints -= node.getCost();
+            skillPoints -= Math.max(0, node.getCost());
         }
     }
 
@@ -126,7 +126,7 @@ public class PlayerSkillData {
         ensureSlotCount();
         int idx = slot - 1;
         if (idx < 0 || idx >= abilityCooldowns.length) return;
-        abilityCooldowns[idx] = ticks;
+        abilityCooldowns[idx] = Math.max(0, ticks);
     }
 
     public int getCooldown(int slot) {
@@ -226,7 +226,7 @@ public class PlayerSkillData {
         int total = 0;
         for (ResourceLocation id : unlockedNodes) {
             SkillNode node = SkillNodeRegistry.get(id);
-            if (node != null) total += node.getCost();
+            if (node != null) total += Math.max(0, node.getCost());
         }
         return total;
     }
@@ -247,7 +247,7 @@ public class PlayerSkillData {
                 return false;
             }
         }
-        skillPoints += node.getCost();
+        skillPoints += Math.max(0, node.getCost());
         rebuildActiveTags();
         return true;
     }
@@ -259,8 +259,9 @@ public class PlayerSkillData {
         for (ResourceLocation id : toRefund) {
             SkillNode node = SkillNodeRegistry.get(id);
             if (node != null && unlockedNodes.remove(id)) {
-                skillPoints += node.getCost();
+                int cost = Math.max(0, node.getCost());
-                refunded += node.getCost();
+                skillPoints += cost;
+                refunded += cost;
             }
         }
         rebuildActiveTags();

src/main/java/net/fretux/skillengine/network/ClientboundSyncSkillDefinitionsPacket.java

@@ -20,6 +20,10 @@ import java.util.function.Supplier;
 
 public class ClientboundSyncSkillDefinitionsPacket {
 
+    private static final int MAX_SYNCED_NODES = 4096;
+    private static final int MAX_LIST_ENTRIES = 512;
+    private static final int MAX_PREREQUISITES = 256;
+
     private final List<SkillNode> skillNodes;
     private final List<AbilityNode> abilityNodes;
 
@@ -42,13 +46,13 @@ public class ClientboundSyncSkillDefinitionsPacket {
     }
 
     public static ClientboundSyncSkillDefinitionsPacket decode(FriendlyByteBuf buf) {
-        int skillNodeCount = buf.readInt();
+        int skillNodeCount = readBoundedCount(buf, MAX_SYNCED_NODES, "skill node definitions");
         List<SkillNode> skillNodes = new ArrayList<>(skillNodeCount);
         for (int i = 0; i < skillNodeCount; i++) {
             skillNodes.add(readSkillNode(buf));
         }
 
-        int abilityNodeCount = buf.readInt();
+        int abilityNodeCount = readBoundedCount(buf, MAX_SYNCED_NODES, "ability node definitions");
         List<AbilityNode> abilityNodes = new ArrayList<>(abilityNodeCount);
         for (int i = 0; i < abilityNodeCount; i++) {
             abilityNodes.add(readAbilityNode(buf));
@@ -136,7 +140,7 @@ public class ClientboundSyncSkillDefinitionsPacket {
     }
 
     private static List<ResourceLocation> readResourceLocationList(FriendlyByteBuf buf) {
-        int size = buf.readInt();
+        int size = readBoundedCount(buf, MAX_LIST_ENTRIES, "resource location list");
         List<ResourceLocation> ids = new ArrayList<>(size);
         for (int i = 0; i < size; i++) {
             ids.add(buf.readResourceLocation());
@@ -153,11 +157,19 @@ public class ClientboundSyncSkillDefinitionsPacket {
     }
 
     private static Map<String, Integer> readPrerequisites(FriendlyByteBuf buf) {
-        int size = buf.readInt();
+        int size = readBoundedCount(buf, MAX_PREREQUISITES, "prerequisites");
         Map<String, Integer> prerequisites = new HashMap<>(size);
         for (int i = 0; i < size; i++) {
             prerequisites.put(buf.readUtf(), buf.readInt());
         }
         return prerequisites;
     }
+
+    private static int readBoundedCount(FriendlyByteBuf buf, int max, String fieldName) {
+        int count = buf.readInt();
+        if (count < 0 || count > max) {
+            throw new IllegalArgumentException("Invalid " + fieldName + " count: " + count);
+        }
+        return count;
+    }
 }

src/main/java/net/fretux/skillengine/network/ClientboundSyncSkillsPacket.java

@@ -12,6 +12,9 @@ import java.util.function.Supplier;
 
 public class ClientboundSyncSkillsPacket {
 
+    private static final int MAX_SYNCED_NODES = 4096;
+    private static final int MAX_ABILITY_SLOTS = 64;
+
     private final Set<ResourceLocation> unlocked;
     private final Set<ResourceLocation> unlockedAbilities;
     private final int skillPoints;
@@ -46,15 +49,15 @@ public class ClientboundSyncSkillsPacket {
     }
 
     public static ClientboundSyncSkillsPacket decode(FriendlyByteBuf buf) {
-        int size = buf.readInt();
+        int size = readBoundedCount(buf, MAX_SYNCED_NODES, "unlocked skill nodes");
         Set<ResourceLocation> unlocked = new HashSet<>();
         for (int i = 0; i < size; i++) unlocked.add(buf.readResourceLocation());
-        int abilitySize = buf.readInt();
+        int abilitySize = readBoundedCount(buf, MAX_SYNCED_NODES, "unlocked abilities");
         Set<ResourceLocation> unlockedAbilities = new HashSet<>();
         for (int i = 0; i < abilitySize; i++) unlockedAbilities.add(buf.readResourceLocation());
         int points = buf.readInt();
-        int slotsCount = buf.readInt();
+        int slotsCount = readBoundedCount(buf, MAX_ABILITY_SLOTS, "ability slots");
-        ResourceLocation[] slots = new ResourceLocation[Math.max(slotsCount, 0)];
+        ResourceLocation[] slots = new ResourceLocation[slotsCount];
         for (int i = 0; i < slots.length; i++) {
             boolean present = buf.readBoolean();
             slots[i] = present ? buf.readResourceLocation() : null;
@@ -76,4 +79,12 @@ public class ClientboundSyncSkillsPacket {
         });
         ctx.get().setPacketHandled(true);
     }
+
+    private static int readBoundedCount(FriendlyByteBuf buf, int max, String fieldName) {
+        int count = buf.readInt();
+        if (count < 0 || count > max) {
+            throw new IllegalArgumentException("Invalid " + fieldName + " count: " + count);
+        }
+        return count;
+    }
 }

src/main/java/net/fretux/skillengine/network/ServerboundActivateAbilityPacket.java

@@ -46,10 +46,11 @@ public class ServerboundActivateAbilityPacket {
                 int cd = data.getCooldown(msg.slot);
                 if (cd > 0) return;
                 ability.execute(player);
-                data.setCooldown(msg.slot, ability.getCooldown());
+                int cooldown = Math.max(0, ability.getCooldown());
+                data.setCooldown(msg.slot, cooldown);
                 PacketHandler.CHANNEL.send(
                         PacketDistributor.PLAYER.with(() -> player),
-                        new ClientboundSyncCooldownPacket(msg.slot, ability.getCooldown())
+                        new ClientboundSyncCooldownPacket(msg.slot, cooldown)
                 );
             });
         });

src/main/java/net/fretux/skillengine/network/ServerboundUnlockNodePacket.java

@@ -42,10 +42,11 @@ public class ServerboundUnlockNodePacket {
                     if (unlockPlan != null) {
                         for (SkillNode plannedNode : unlockPlan) {
                             data.unlockNode(plannedNode);
-                            if (plannedNode.getCost() > 0) {
+                            int cost = Math.max(0, plannedNode.getCost());
+                            if (cost > 0) {
                                 MinecraftForge.EVENT_BUS.post(new SkillPointsChangedEvent(
                                         player,
-                                        plannedNode.getCost(),
+                                        cost,
                                         SkillPointsChangedEvent.Reason.SPENT,
                                         plannedNode.getId()
                                 ));

src/main/java/net/fretux/skillengine/skilltree/SkillLogic.java

@@ -33,7 +33,7 @@ public class SkillLogic {
 
         int totalCost = 0;
         for (SkillNode plannedNode : plan) {
-            totalCost += plannedNode.getCost();
+            totalCost += Math.max(0, plannedNode.getCost());
         }
         if (data.getSkillPoints() < totalCost) {
             return Optional.empty();

src/main/java/net/fretux/skillengine/skilltree/SkillTreeValidator.java

@@ -33,6 +33,9 @@ public final class SkillTreeValidator {
         if (!isPngTexture(node.getIcons())) {
             issues.add(node.getId() + " has invalid icon path " + node.getIcons() + " (expected a .png texture)");
         }
+        if (node.getCost() < 0) {
+            issues.add(node.getId() + " has negative cost " + node.getCost());
+        }
         for (ResourceLocation parent : node.getLinks()) {
             if (SkillNodeRegistry.get(parent) == null) {
                 issues.add(node.getId() + " links to missing skill node " + parent);
@@ -83,6 +86,9 @@ public final class SkillTreeValidator {
         if (!isPngTexture(ability.getIcon())) {
             issues.add(ability.getId() + " has invalid icon path " + ability.getIcon() + " (expected a .png texture)");
         }
+        if (ability.getCooldown() < 0) {
+            issues.add(ability.getId() + " has negative cooldown " + ability.getCooldown());
+        }
         for (ResourceLocation parent : ability.getLinks()) {
             if (SkillNodeRegistry.get(parent) == null && AbilityNodeRegistry.get(parent) == null) {
                 issues.add(ability.getId() + " links to missing node or ability " + parent);