move demo/static/src/ts/core to src/

src/event_bus.ts

@@ -0,0 +1,77 @@
+/**
+ * We define here a simple event bus: it can
+ * - emit events
+ * - add/remove listeners.
+ *
+ * This is a useful pattern of communication in some cases.
+ */
+
+//------------------------------------------------------------------------------
+// Types
+//------------------------------------------------------------------------------
+
+export type Callback = (...args: any[]) => void;
+
+export interface Subscription {
+  owner: any;
+  callback: Callback;
+}
+
+//------------------------------------------------------------------------------
+// EventBus
+//------------------------------------------------------------------------------
+
+export class EventBus {
+  subscriptions: { [eventType: string]: Subscription[] } = {};
+
+  /**
+   * Add a listener for the 'eventType' events.
+   *
+   * Note that the 'owner' of this event can be anything, but will more likely
+   * be a widget or a class. The idea is that the callback will be called with
+   * the proper owner bound.
+   *
+   * Also, the owner should be kind of unique. This will be used to remove the
+   * listener.
+   */
+  on(eventType: string, owner: any, callback: Callback) {
+    if (!callback) {
+      throw new Error("Missing callback");
+    }
+    if (!this.subscriptions[eventType]) {
+      this.subscriptions[eventType] = [];
+    }
+    this.subscriptions[eventType].push({
+      owner,
+      callback
+    });
+  }
+
+  /**
+   * Remove a listener
+   */
+  off(eventType: string, owner: any) {
+    const subs = this.subscriptions[eventType];
+    if (subs) {
+      this.subscriptions[eventType] = subs.filter(s => s.owner !== owner);
+    }
+  }
+
+  /**
+   * Emit an event of type 'eventType'.  Any extra arguments will be passed to
+   * the listeners callback.
+   */
+  trigger(eventType: string, ...args: any[]) {
+    const subs = this.subscriptions[eventType] || [];
+    for (let sub of subs) {
+      sub.callback.call(sub.owner, ...args);
+    }
+  }
+
+  /**
+   * Remove all subscriptions.
+   */
+  clear() {
+    this.subscriptions = {};
+  }
+}