add bus class

web/static/src/ts/core/bus.ts

@@ -0,0 +1,32 @@
+type Callback = (...args: any[]) => void;
+
+interface Subscription {
+  owner: any;
+  callback: Callback;
+}
+
+export default class Bus {
+  private subscriptions: { [eventType: string]: Subscription[] } = {};
+
+  on(eventType: string, owner: any, callback: Callback) {
+    if (!this.subscriptions[eventType]) {
+      this.subscriptions[eventType] = [];
+    }
+    this.subscriptions[eventType].push({
+      owner,
+      callback
+    });
+  }
+  off(eventType: string, owner: any) {
+    const subs = this.subscriptions[eventType];
+    if (subs) {
+      this.subscriptions[eventType] = subs.filter(s => s.owner !== owner);
+    }
+  }
+  trigger(eventType: string, ...args: any[]) {
+    const subs = this.subscriptions[eventType] || [];
+    for (let sub of subs) {
+      sub.callback(...args);
+    }
+  }
+}