feat(notifications): implement notification service

services/Notifications.qml

@@ -0,0 +1,74 @@
+pragma Singleton
+
+import QtQuick
+import Quickshell
+import Quickshell.Services.Notifications
+
+Singleton {
+    id: root
+
+    // Notifications currently shown in the OSD, tracked by the server.
+    readonly property alias popups: server.trackedNotifications
+    readonly property int popupCount: popups.values.length
+
+    // Do-not-disturb: notifications are recorded but not displayed.
+    property bool dnd: false
+
+    // Maximum amount of simultaneously displayed popups.
+    property int maxPopups: 5
+
+    // History of received notifications (newest first), for future dashboards.
+    property var history: []
+    property int historyLimit: 100
+
+    NotificationServer {
+        id: server
+
+        keepOnReload: false
+
+        bodySupported: true
+        bodyMarkupSupported: true
+        actionsSupported: true
+
+        onNotification: notification => {
+            root.addHistory(notification);
+
+            if (root.dnd || notification.transient)
+                return;
+
+            notification.tracked = true;
+
+            const tracked = server.trackedNotifications.values;
+            if (tracked.length > root.maxPopups)
+                tracked[0].expire();
+        }
+    }
+
+    function clearHistory(): void {
+        root.history = [];
+    }
+
+    function addHistory(notification: Notification): void {
+        const entry = {
+            id: notification.id,
+            appName: notification.appName,
+            appIcon: notification.appIcon,
+            desktopEntry: notification.desktopEntry,
+            summary: notification.summary,
+            body: notification.body,
+            image: notification.image,
+            urgency: notification.urgency,
+            transient: notification.transient,
+            time: Date.now(),
+            actions: notification.actions.map(action => ({
+                        identifier: action.identifier,
+                        text: action.text
+                    }))
+        };
+
+        let next = [entry, ...root.history];
+        if (next.length > root.historyLimit)
+            next = next.slice(0, root.historyLimit);
+        root.history = next;
+    }
+}