Check for conflicts when mapping items

src/main/java/org/geysermc/packgenerator/mappings/GeyserMapping.java

@@ -55,4 +55,20 @@ public record GeyserMapping(ResourceLocation model, ResourceLocation bedrockIden
                 ).apply(instance, BedrockOptions::new)
         );
     }
+
+    public boolean conflictsWith(GeyserMapping other) {
+        if (!model.equals(other.model)) {
+            return false;
+        } else if (predicates.size() == other.predicates.size()) {
+            boolean predicatesAreEqual = true;
+            for (GeyserPredicate predicate : predicates) {
+                if (!other.predicates.contains(predicate)) {
+                    predicatesAreEqual = false;
+                    break;
+                }
+            }
+            return predicatesAreEqual;
+        }
+        return false;
+    }
 }

src/main/java/org/geysermc/packgenerator/mappings/GeyserMappings.java

@@ -39,7 +39,11 @@ public class GeyserMappings {
     }
 
     public void map(Holder<Item> item, GeyserMapping mapping) {
-        // TODO conflict detection
+        for (GeyserMapping existing : mappings.get(item)) {
+            if (existing.conflictsWith(mapping)) {
+                throw new IllegalArgumentException("Mapping conflicts with existing mapping");
+            }
+        }
         mappings.put(item, mapping);
     }