feat: observable pattern

Author: hamed-musallam

src/observables/index.ts

@@ -0,0 +1,44 @@
+import { Subject, Observer } from './subject';
+import { EventData, EventType } from '../actions/types';
+
+const NAMESPACE = '__nmrium_events__';
+
+function initSubject(event: EventType) {
+  if (!window?.[NAMESPACE]?.[event]) {
+    window[NAMESPACE] = {
+      ...window[NAMESPACE],
+      [event]: new Subject(),
+    };
+  }
+}
+
+function trigger<T extends EventType>(event: T, data: EventData<T>) {
+  initSubject(event);
+  window[NAMESPACE][event].notify(data);
+}
+
+function unsubscribe(event: EventType, observerID: string) {
+  return () => {
+    if (window?.[NAMESPACE]?.[event]) {
+      window[NAMESPACE][event].unsubscribe(observerID);
+    } else {
+      throw new Error('No event Registered');
+    }
+  };
+}
+
+function subscribe<T extends EventType>(
+  event: T,
+  onData: (data: EventData<T>) => void,
+) {
+  initSubject(event);
+  const id = Math.random().toString(36).slice(2, 9);
+
+  const observer: Observer = { id, update: onData } as Observer;
+
+  (window[NAMESPACE][event] as Subject).subscribe(observer);
+
+  return unsubscribe(event, id);
+}
+
+export default { trigger, subscribe };

src/observables/subject.ts

@@ -0,0 +1,24 @@
+export interface Observer {
+  readonly id: string;
+  update: (data: unknown) => void;
+}
+
+export class Subject {
+  private observers: Observer[] = [];
+
+  subscribe(observer: Observer) {
+    this.observers.push(observer);
+  }
+
+  unsubscribe(observerID: string) {
+    this.observers = this.observers.filter((_observer) => {
+      return _observer.id !== observerID;
+    });
+  }
+
+  notify(data: unknown) {
+    this.observers.forEach((observer) => {
+      observer.update(data);
+    });
+  }
+}