1 files changed, 114 insertions, 0 deletions
diff --git a/FrontEnd/src/components/alert/AlertService.ts b/FrontEnd/src/components/alert/AlertService.ts
new file mode 100644
index 00000000..b9cda752
--- /dev/null
+++ b/FrontEnd/src/components/alert/AlertService.ts
@@ -0,0 +1,114 @@
+import { ThemeColor, Text } from "../common";
+
+const defaultDismissTime = 5000;
+
+export interface AlertInfo {
+  color?: ThemeColor;
+  message: Text;
+  dismissTime?: number | "never";
+}
+
+export interface AlertInfoWithId extends AlertInfo {
+  id: number;
+}
+
+interface AlertServiceAlert extends AlertInfoWithId {
+  timerId: number | null;
+}
+
+export type AlertsListener = (alerts: AlertInfoWithId[]) => void;
+
+export class AlertService {
+  private listeners: AlertsListener[] = [];
+  private alerts: AlertServiceAlert[] = [];
+  private currentId = 1;
+
+  getAlert(alertId?: number | null | undefined): AlertServiceAlert | null {
+    for (const alert of this.alerts) {
+      if (alert.id === alertId) return alert;
+    }
+    return null;
+  }
+
+  registerListener(listener: AlertsListener): void {
+    this.listeners.push(listener);
+    listener(this.alerts);
+  }
+
+  unregisterListener(listener: AlertsListener): void {
+    this.listeners = this.listeners.filter((l) => l !== listener);
+  }
+
+  notify() {
+    for (const listener of this.listeners) {
+      listener(this.alerts);
+    }
+  }
+
+  push(alert: AlertInfo): void {
+    const newAlert: AlertServiceAlert = {
+      ...alert,
+      id: this.currentId++,
+      timerId: null,
+    };
+
+    this.alerts = [...this.alerts, newAlert];
+    this._resetDismissTimer(newAlert);
+
+    this.notify();
+  }
+
+  private _dismiss(alert: AlertServiceAlert) {
+    if (alert.timerId != null) {
+      window.clearTimeout(alert.timerId);
+    }
+    this.alerts = this.alerts.filter((a) => a !== alert);
+    this.notify();
+  }
+
+  dismiss(alertId?: number | null | undefined) {
+    const alert = this.getAlert(alertId);
+    if (alert != null) {
+      this._dismiss(alert);
+    }
+  }
+
+  private _clearDismissTimer(alert: AlertServiceAlert) {
+    if (alert.timerId != null) {
+      window.clearTimeout(alert.timerId);
+      alert.timerId = null;
+    }
+  }
+
+  clearDismissTimer(alertId?: number | null | undefined) {
+    const alert = this.getAlert(alertId);
+    if (alert != null) {
+      this._clearDismissTimer(alert);
+    }
+  }
+
+  private _resetDismissTimer(
+    alert: AlertServiceAlert,
+    dismissTime?: number | null | undefined,
+  ) {
+    this._clearDismissTimer(alert);
+
+    const realDismissTime =
+      dismissTime ?? alert.dismissTime ?? defaultDismissTime;
+
+    if (typeof realDismissTime === "number") {
+      alert.timerId = window.setTimeout(() => {
+        this._dismiss(alert);
+      }, realDismissTime);
+    }
+  }
+
+  resetDismissTimer(alertId?: number | null | undefined) {
+    const alert = this.getAlert(alertId);
+    if (alert != null) {
+      this._resetDismissTimer(alert);
+    }
+  }
+}
+
+export const alertService = new AlertService();