1 files changed, 59 insertions, 0 deletions
diff --git a/Timeline/ClientApp/src/common/alert-service.ts b/Timeline/ClientApp/src/common/alert-service.ts
new file mode 100644
index 00000000..305752eb
--- /dev/null
+++ b/Timeline/ClientApp/src/common/alert-service.ts
@@ -0,0 +1,59 @@
+import pull from 'lodash/pull';
+
+export interface AlertInfo {
+  type?: 'primary' | 'secondary' | 'success' | 'danger' | 'warning' | 'info';
+  message: string;
+}
+
+export interface AlertInfoEx extends AlertInfo {
+  id: number;
+}
+
+export type AlertConsumer = (alerts: AlertInfoEx) => void;
+
+export class AlertService {
+  private consumers: AlertConsumer[] = [];
+  private savedAlerts: AlertInfoEx[] = [];
+  private currentId = 1;
+
+  private produce(alert: AlertInfoEx): void {
+    for (const consumer of this.consumers) {
+      consumer(alert);
+    }
+  }
+
+  registerConsumer(consumer: AlertConsumer): void {
+    this.consumers.push(consumer);
+    if (this.savedAlerts.length !== 0) {
+      for (const alert of this.savedAlerts) {
+        this.produce(alert);
+      }
+      this.savedAlerts = [];
+    }
+  }
+
+  unregisterConsumer(consumer: AlertConsumer): void {
+    pull(this.consumers, consumer);
+  }
+
+  push(alert: AlertInfo): void {
+    const newAlert: AlertInfoEx = { ...alert, id: this.currentId++ };
+    if (this.consumers.length === 0) {
+      this.savedAlerts.push(newAlert);
+    } else {
+      this.produce(newAlert);
+    }
+  }
+}
+
+export const alertService = new AlertService();
+
+export function pushAlert(alert: AlertInfo): void {
+  alertService.push(alert);
+}
+
+export const kAlertHostId = 'alert-host';
+
+export function getAlertHost(): HTMLElement | null {
+  return document.getElementById(kAlertHostId);
+}