feat: indexed zipper (#378)

Author: Tchips46

packages/ecs-lib/lib/libecs.d.ts

@@ -50,6 +50,7 @@ export interface Registry extends ClassHandle {
   getComponents(_0: Component): SparseArray;
   spawnEntity(): Entity;
   getZipper(_0: Component[]): any[];
+  getIndexedZipper(_0: Component[]): any[];
   killEntity(_0: Entity): void;
   clearEntities(): void;
   removeComponent(_0: Entity, _1: Component): void;

packages/ecs-lib/test/Zipper.spec.ts

@@ -97,18 +97,35 @@ describe("Zipper", () => {
       let zip = r.getZipper([Velocity]);
       expect(zip).toBeDefined();
 
-      for (let i = 0; i < 20; i++) {
-        if (zip[i]) {
-          zip[i]["Velocity"].y *= 2;
-        }
-      }
+      zip.forEach(({ Velocity }) => {
+        Velocity.y *= 2;
+      });
 
       zip = r.getZipper([Velocity]);
+      expect(zip).toBeDefined();
+
+      zip.forEach((entity) => {
+        expect(entity).toStrictEqual({ Velocity: new Velocity(0, 2) });
+      });
+    });
+  });
+
+  describe("indexed zipper", () => {
+    it("should reflect index of the zipped entities components", async () => {
+      const m = await Module();
+      const r = new m.Registry();
+
       for (let i = 0; i < 20; i++) {
-        if (zip[i]) {
-          expect(zip[i]).toStrictEqual({ Velocity: new Velocity(0, 2) });
-        }
+        const e = r.spawnEntity();
+        if (i % 5 === 0) r.addComponent(e, new Velocity(0, i));
       }
+
+      const zip = r.getIndexedZipper([Velocity]);
+      expect(zip).toBeDefined();
+
+      zip.forEach((entity, index) => {
+        expect(entity).toStrictEqual({ id: index * 5, Velocity: new Velocity(0, index * 5) });
+      });
     });
   });
 });

packages/ecs-lib/wasm/Registry.cpp

@@ -57,6 +57,7 @@ namespace nfo {
             .function("removeSystem", &Registry::remove_system)
             .function("clearSystems", &Registry::clear_systems)
             .function("getZipper", &Registry::get_zipper)
+            .function("getIndexedZipper", &Registry::get_indexed_zipper)
             .function("maxEntities", &Registry::max_entities);
     }
 } // namespace nfo

packages/ecs-lib/wasm/Registry.hpp

@@ -323,6 +323,46 @@ namespace nfo {
             return ZipperOutput(arr);
         }
 
+        /**
+         * Get the indexed zipper output for the given components.
+         *
+         * @param comps An array of component types to zip.
+         * @return A ZipperOutput containing the id of the entity and it's zipped components.
+         * @throws std::runtime_error if the input is not an array.
+         */
+        ZipperOutput get_indexed_zipper(const ZipperInput &comps)
+        {
+            if (!comps.isArray())
+                throw std::runtime_error("getIndexedZipper: need an array of comps as parameter");
+
+            std::size_t max = SIZE_MAX;
+            std::map<std::string, SparseArray<emscripten::val> *> arrays;
+            for (int i = 0; i < comps["length"].as<unsigned int>(); i++) {
+                SparseArray<emscripten::val> &components = get_components(Component(comps[i]));
+                arrays[get_js_class_name(comps[i])] = &components;
+                max = (std::min)(components.size(), max);
+            }
+
+            emscripten::val arr = emscripten::val::array();
+            std:size_t zipper_idx = 0;
+            for (std::size_t idx = 0; idx < max; idx++) {
+                emscripten::val obj = emscripten::val::object();
+                bool need_to_add = true;
+                for (const auto &[name, sparse_array] : arrays) {
+                    if (!(*sparse_array)[idx].has_value()) {
+                        need_to_add = false;
+                        break;
+                    }
+                    obj.set(name, (*sparse_array)[idx].value());
+                }
+                if (need_to_add) {
+                    obj.set("id", idx);
+                    arr.set(zipper_idx++, obj);
+                }
+            }
+            return ZipperOutput(arr);
+        }
+
       private:
         std::unordered_map<std::string, std::any> _components_arrays;