feat: apply

src/ecs.js

@@ -9,6 +9,7 @@ class Ecs {
   Components = {};
   entities = new Map();
   Systems = {};
+  tracking = true;
 
   constructor({Components, Systems}) {
     for (const componentName in Components) {
@@ -31,6 +32,38 @@ class Ecs {
     };
   }
 
+  apply(diff) {
+    const {tracking} = this;
+    this.tracking = false;
+    for (const [entityId, change] of diff) {
+      const entity = this.entities.get(entityId);
+      if (false === change) {
+        this.destroyImmediately(entity);
+        continue;
+      }
+      if (!entity) {
+        this.createSpecific(entityId, change);
+        continue;
+      }
+      for (const componentName in change) {
+        const values = change[componentName];
+        const Component = this.Components[componentName];
+        if (false === values) {
+          entity.removeComponent(Component);
+          continue;
+        }
+        if (!entity.has(componentName)) {
+          entity.addComponent(Component, values);
+          continue;
+        }
+        for (const key in values) {
+          entity[componentName][key] = values[key];
+        }
+      }
+    }
+    this.tracking = tracking;
+  }
+
   create(components = {}) {
     return this.createSpecific(this.nextId(), components);
   }
@@ -117,8 +150,10 @@ class Ecs {
   }
 
   markChange(entityId, componentName, change) {
-    this.$$diff = undefined;
-    this.changes.push({entityId, componentName, change});
+    if (this.tracking) {
+      this.$$diff = undefined;
+      this.changes.push({entityId, componentName, change});
+    }
   }
 
   static merge(l, r) {

src/ecs.test.js

@@ -106,3 +106,21 @@ test('serialization', async () => {
   schema.encode(ecs.diff(), view);
   expect(schema.decode(view)).to.deep.equal(ecs.diff());
 });
+
+test('apply', () => {
+  const ecs = new Ecs({Components: {A}, Systems: {}});
+  ecs.apply(new Map([[32, {}]]))
+  const entity = ecs.entities.get(32);
+  expect(entity).not.to.be.undefined;
+  expect(entity.has('A')).to.be.false;
+  ecs.apply(new Map([[32, {A: {}}]]))
+  expect(entity.has('A')).to.be.true;
+  expect(entity.A.a).to.equal(64);
+  ecs.apply(new Map([[32, {A: {a: 128}}]]))
+  expect(entity.A.a).to.equal(128);
+  ecs.apply(new Map([[32, {A: false}]]))
+  expect(entity.has('A')).to.be.false;
+  ecs.apply(new Map([[32, false]]))
+  expect(ecs.entities.get(32)).to.be.undefined;
+  expect(ecs.diff()).to.deep.equal(new Map());
+});