From aa08a8943a9a2d4a0e51893eebe6900bca7a7251 Mon Sep 17 00:00:00 2001
From: Elizabeth Hunt <elizabeth.hunt@simponic.xyz>
Date: Fri, 1 Mar 2024 16:45:58 -0700
Subject: ecs init

---
 src/engine/index.ts | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 src/engine/index.ts

(limited to 'src/engine/index.ts')

diff --git a/src/engine/index.ts b/src/engine/index.ts
new file mode 100644
index 0000000..2df9f17
--- /dev/null
+++ b/src/engine/index.ts
@@ -0,0 +1,90 @@
+import { Entity } from "./entities";
+import { System } from "./systems";
+
+export class Game {
+  private systemOrder: string[];
+
+  private running: boolean;
+  private lastTimeStamp: number;
+
+  public entities: Map<string, Entity>;
+  public systems: Map<string, System>;
+  public componentEntities: Map<string, Set<string>>;
+
+  constructor() {
+    this.lastTimeStamp = performance.now();
+    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: string): Entity | undefined {
+    return this.entities.get(id);
+  }
+
+  public removeEntity(id: string) {
+    this.entities.delete(id);
+  }
+
+  public forEachEntityWithComponent(
+    componentName: string,
+    callback: (entity: Entity) => void,
+  ) {
+    this.componentEntities.get(componentName)?.forEach((entityId) => {
+      const entity = this.getEntity(entityId);
+      if (!entity) return;
+
+      callback(entity);
+    });
+  }
+
+  public addSystem(system: System) {
+    if (!this.systemOrder.includes(system.name)) {
+      this.systemOrder.push(system.name);
+    }
+    this.systems.set(system.name, system);
+  }
+
+  public getSystem<T>(name: string): T {
+    return this.systems.get(name) as unknown as T;
+  }
+
+  public doGameLoop(timeStamp: number) {
+    if (!this.running) {
+      return;
+    }
+
+    const dt = timeStamp - this.lastTimeStamp;
+    this.lastTimeStamp = timeStamp;
+
+    // rebuild the Component -> { Entity } map
+    this.componentEntities.clear();
+    this.entities.forEach((entity) =>
+      entity.getComponents().forEach((component) => {
+        if (!this.componentEntities.has(component.name)) {
+          this.componentEntities.set(
+            component.name,
+            new Set<string>([entity.id]),
+          );
+          return;
+        }
+        this.componentEntities.get(component.name)?.add(entity.id);
+      }),
+    );
+
+    this.systemOrder.forEach((systemName) => {
+      this.systems.get(systemName)?.update(dt, this);
+    });
+  }
+}
-- 
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