refactor: tighten project structure and strengthen tooling

src/utils/EventEmitter.ts

@@ -1 +1,54 @@
-// src/utils/EventEmitter.ts
+type Listener<TPayload> = (payload: TPayload) => void;
+
+export class EventEmitter<TEvents extends Record<string, unknown>> {
+  private readonly listeners = new Map<
+    keyof TEvents,
+    Set<Listener<TEvents[keyof TEvents]>>
+  >();
+
+  on<TKey extends keyof TEvents>(
+    event: TKey,
+    listener: Listener<TEvents[TKey]>,
+  ): () => void {
+    const currentListeners = this.listeners.get(event) ?? new Set();
+    currentListeners.add(listener as Listener<TEvents[keyof TEvents]>);
+    this.listeners.set(event, currentListeners);
+
+    return () => {
+      this.off(event, listener);
+    };
+  }
+
+  off<TKey extends keyof TEvents>(
+    event: TKey,
+    listener: Listener<TEvents[TKey]>,
+  ): void {
+    const currentListeners = this.listeners.get(event);
+
+    if (!currentListeners) {
+      return;
+    }
+
+    currentListeners.delete(listener as Listener<TEvents[keyof TEvents]>);
+
+    if (currentListeners.size === 0) {
+      this.listeners.delete(event);
+    }
+  }
+
+  emit<TKey extends keyof TEvents>(event: TKey, payload: TEvents[TKey]): void {
+    const currentListeners = this.listeners.get(event);
+
+    if (!currentListeners) {
+      return;
+    }
+
+    currentListeners.forEach((listener) => {
+      listener(payload as TEvents[keyof TEvents]);
+    });
+  }
+
+  clear(): void {
+    this.listeners.clear();
+  }
+}