1 files changed, 76 insertions, 0 deletions
diff --git a/engine/Game.ts b/engine/Game.ts
new file mode 100644
index 0000000..c2a2c4f
--- /dev/null
+++ b/engine/Game.ts
@@ -0,0 +1,76 @@
+import { Entity } from "./entities";
+import { System } from "./systems";
+
+export class Game {
+  private systemOrder: string[];
+
+  private running: boolean;
+  private lastTimeStamp: number;
+
+  public entities: Map<number, Entity>;
+  public systems: Map<string, System>;
+  public componentEntities: Map<string, Set<number>>;
+
+  constructor() {
+    this.running = false;
+    this.systemOrder = [];
+    this.systems = new Map();
+    this.entities = new Map();
+    this.componentEntities = new Map();
+  }
+
+  public start() {
+    this.lastTimeStamp = performance.now();
+    this.running = true;
+  }
+
+  public addEntity(entity: Entity) {
+    this.entities.set(entity.id, entity);
+  }
+
+  public getEntity(id: number): Entity {
+    return this.entities.get(id);
+  }
+
+  public removeEntity(id: number) {
+    this.entities.delete(id);
+  }
+
+  public addSystem(system: System) {
+    if (!this.systemOrder.includes(system.name)) {
+      this.systemOrder.push(system.name);
+    }
+    this.systems.set(system.name, system);
+  }
+
+  public getSystem(name: string): System {
+    return this.systems.get(name);
+  }
+
+  public doGameLoop = (timeStamp: number) => {
+    if (!this.running) {
+      return;
+    }
+
+    const dt = timeStamp - this.lastTimeStamp;
+    this.lastTimeStamp = timeStamp;
+
+    this.componentEntities.clear();
+    this.entities.forEach((entity) =>
+      entity.getComponents().forEach((component) => {
+        if (!this.componentEntities.has(component.name)) {
+          this.componentEntities.set(
+            component.name,
+            new Set<number>([entity.id])
+          );
+          return;
+        }
+        this.componentEntities.get(component.name).add(entity.id);
+      })
+    );
+
+    this.systemOrder.forEach((systemName) => {
+      this.systems.get(systemName).update(dt, this);
+    });
+  };
+}