Use a persistent notifications model to improve load times of the notifications view

src/state/models/me.ts

@@ -1,6 +1,7 @@
 import {makeAutoObservable, runInAction} from 'mobx'
 import {RootStoreModel} from './root-store'
 import {MembershipsViewModel} from './memberships-view'
+import {NotificationsViewModel} from './notifications-view'
 
 export class MeModel {
   did?: string
@@ -9,9 +10,11 @@ export class MeModel {
   description?: string
   notificationCount: number = 0
   memberships?: MembershipsViewModel
+  notifications: NotificationsViewModel
 
   constructor(public rootStore: RootStoreModel) {
     makeAutoObservable(this, {rootStore: false}, {autoBind: true})
+    this.notifications = new NotificationsViewModel(this.rootStore, {})
   }
 
   clear() {
@@ -43,7 +46,12 @@ export class MeModel {
       this.memberships = new MembershipsViewModel(this.rootStore, {
         actor: this.did,
       })
-      await this.memberships?.setup()
+      await this.memberships?.setup().catch(e => {
+        console.error('Failed to setup memberships model', e)
+      })
+      await this.notifications.setup().catch(e => {
+        console.error('Failed to setup notifications model', e)
+      })
     } else {
       this.clear()
     }
@@ -56,7 +64,12 @@ export class MeModel {
   async fetchStateUpdate() {
     const res = await this.rootStore.api.app.bsky.notification.getCount()
     runInAction(() => {
+      const newNotifications = this.notificationCount !== res.data.count
       this.notificationCount = res.data.count
+      if (newNotifications) {
+        // trigger pre-emptive fetch on new notifications
+        this.notifications.refresh()
+      }
     })
   }
 

src/state/models/notifications-view.ts

@@ -203,7 +203,6 @@ export class NotificationsViewModel {
     await this._pendingWork()
     this._loadPromise = this._initialLoad(isRefreshing)
     await this._loadPromise
-    this._updateReadState()
     this._loadPromise = undefined
   }
 
@@ -240,6 +239,20 @@ export class NotificationsViewModel {
     this._updatePromise = undefined
   }
 
+  /**
+   * Update read/unread state
+   */
+  async updateReadState() {
+    try {
+      await this.rootStore.api.app.bsky.notification.updateSeen({
+        seenAt: new Date().toISOString(),
+      })
+      this.rootStore.me.clearNotificationCount()
+    } catch (e) {
+      console.log('Failed to update notifications read state', e)
+    }
+  }
+
   // state transitions
   // =
 
@@ -329,11 +342,10 @@ export class NotificationsViewModel {
   }
 
   private async _replaceAll(res: ListNotifications.Response) {
-    this.notifications.length = 0
-    return this._appendAll(res)
+    return this._appendAll(res, true)
   }
 
-  private async _appendAll(res: ListNotifications.Response) {
+  private async _appendAll(res: ListNotifications.Response, replace = false) {
     this.loadMoreCursor = res.data.cursor
     this.hasMore = !!this.loadMoreCursor
     let counter = this.notifications.length
@@ -357,7 +369,11 @@ export class NotificationsViewModel {
       )
     })
     runInAction(() => {
-      this.notifications = this.notifications.concat(itemModels)
+      if (replace) {
+        this.notifications = itemModels
+      } else {
+        this.notifications = this.notifications.concat(itemModels)
+      }
     })
   }
 
@@ -374,17 +390,6 @@ export class NotificationsViewModel {
       }
     }
   }
-
-  private async _updateReadState() {
-    try {
-      await this.rootStore.api.app.bsky.notification.updateSeen({
-        seenAt: new Date().toISOString(),
-      })
-      this.rootStore.me.clearNotificationCount()
-    } catch (e) {
-      console.log('Failed to update notifications read state', e)
-    }
-  }
 }
 
 function groupNotifications(