Implement new structure

src/common/emitter.ts

@@ -0,0 +1,40 @@
+export interface Disposable {
+  dispose(): void
+}
+
+export interface Event<T> {
+  (listener: (value: T) => void): Disposable
+}
+
+/**
+ * Emitter typecasts for a single event type.
+ */
+export class Emitter<T> {
+  private listeners: Array<(value: T) => void> = []
+
+  public get event(): Event<T> {
+    return (cb: (value: T) => void): Disposable => {
+      this.listeners.push(cb)
+
+      return {
+        dispose: (): void => {
+          const i = this.listeners.indexOf(cb)
+          if (i !== -1) {
+            this.listeners.splice(i, 1)
+          }
+        },
+      }
+    }
+  }
+
+  /**
+   * Emit an event with a value.
+   */
+  public emit(value: T): void {
+    this.listeners.forEach((cb) => cb(value))
+  }
+
+  public dispose(): void {
+    this.listeners = []
+  }
+}