[Add] Asset Validator

Assets/Features/VoxelWorld/Runtime/WorldPrefabCollection.cs

@@ -106,6 +106,111 @@ namespace InfiniteWorld.VoxelWorld
         public bool HasPrefab { get; }
     }
 
+    internal static class WorldPlacementValidation
+    {
+        public static bool TryGetCollectionBlockerReason(WorldPrefabCollection collection, out string reason)
+        {
+            if (collection == null)
+            {
+                reason = "collection reference is missing.";
+                return true;
+            }
+
+            if (collection.maxPlacementsPerChunk <= 0)
+            {
+                reason = "max placements per chunk must be greater than 0.";
+                return true;
+            }
+
+            if (collection.attemptsPerPlacement < 1)
+            {
+                reason = "attempts per placement must be at least 1.";
+                return true;
+            }
+
+            if (collection.chunkEdgePadding < 0)
+            {
+                reason = "chunk edge padding cannot be negative.";
+                return true;
+            }
+
+            if (collection.entries == null || collection.entries.Count == 0)
+            {
+                reason = "collection has no entries configured.";
+                return true;
+            }
+
+            reason = null;
+            return false;
+        }
+
+        public static bool TryGetEntryBlockerReason(WorldPrefabEntry entry, HashSet<string> usedIds, out string reason)
+        {
+            if (entry == null)
+            {
+                reason = "entry reference is missing.";
+                return true;
+            }
+
+            if (string.IsNullOrWhiteSpace(entry.id))
+            {
+                reason = "id is empty. A stable id is required for deterministic spawns and save data.";
+                return true;
+            }
+
+            if (usedIds != null && !usedIds.Add(entry.id))
+            {
+                reason = $"duplicate id '{entry.id}' in the same collection.";
+                return true;
+            }
+
+            if (entry.prefab == null)
+            {
+                reason = "prefab is missing.";
+                return true;
+            }
+
+            if (entry.weight <= 0f)
+            {
+                reason = "weight must be greater than 0.";
+                return true;
+            }
+
+            if (entry.spawnChancePercent <= 0f)
+            {
+                reason = "spawn chance must be greater than 0%.";
+                return true;
+            }
+
+            if (entry.footprint.x <= 0 || entry.footprint.y <= 0)
+            {
+                reason = "footprint must be at least 1x1.";
+                return true;
+            }
+
+            if (entry.clearance < 0)
+            {
+                reason = "clearance cannot be negative.";
+                return true;
+            }
+
+            if (entry.flattenPadding < 0)
+            {
+                reason = "flatten padding cannot be negative.";
+                return true;
+            }
+
+            if (entry.placementMode == WorldPlacementMode.FlattenTerrain && entry.flattenSearchRadius < 1)
+            {
+                reason = "flatten search radius must be at least 1 for FlattenTerrain mode.";
+                return true;
+            }
+
+            reason = null;
+            return false;
+        }
+    }
+
     public sealed class WorldTerrainPatch
     {
         private readonly List<Vector2Int> flattenedCells;