Fix pagination and rendering of suggested follows (#95)

src/state/models/suggested-actors-view.ts

@@ -2,9 +2,9 @@ import {makeAutoObservable} from 'mobx'
 import {AppBskyActorGetSuggestions as GetSuggestions} from '@atproto/api'
 import {RootStoreModel} from './root-store'
 
-export type SuggestedActor = GetSuggestions.Actor & {
-  _reactKey: string
-}
+const PAGE_SIZE = 30
+
+export type SuggestedActor = GetSuggestions.Actor
 
 export class SuggestedActorsViewModel {
   // state
@@ -12,6 +12,9 @@ export class SuggestedActorsViewModel {
   isRefreshing = false
   hasLoaded = false
   error = ''
+  hasMore = true
+  loadMoreCursor?: string
+  private _loadMorePromise: Promise<void> | undefined
 
   // data
   suggestions: SuggestedActor[] = []
@@ -41,12 +44,17 @@ export class SuggestedActorsViewModel {
   // public api
   // =
 
-  async setup() {
-    await this._fetch()
+  async refresh() {
+    return this.loadMore(true)
   }
 
-  async refresh() {
-    await this._fetch(true)
+  async loadMore(isRefreshing = false) {
+    if (this._loadMorePromise) {
+      return this._loadMorePromise
+    }
+    this._loadMorePromise = this._loadMore(isRefreshing)
+    await this._loadMorePromise
+    this._loadMorePromise = undefined
   }
 
   // state transitions
@@ -71,46 +79,43 @@ export class SuggestedActorsViewModel {
   // loader functions
   // =
 
-  private async _fetch(isRefreshing = false) {
-    this.suggestions.length = 0
+  private async _loadMore(isRefreshing = false) {
+    if (!this.hasMore) {
+      return
+    }
     this._xLoading(isRefreshing)
-    let cursor
-    let res
     try {
+      if (this.isRefreshing) {
+        this.suggestions = []
+      }
+      let res
+      let totalAdded = 0
       do {
         res = await this.rootStore.api.app.bsky.actor.getSuggestions({
-          limit: 20,
-          cursor,
+          limit: PAGE_SIZE,
+          cursor: this.loadMoreCursor,
         })
-        this._appendAll(res)
-        cursor = res.data.cursor
-      } while (
-        cursor &&
-        res.data.actors.length === 20 &&
-        this.suggestions.length < 20
-      )
+        totalAdded += await this._appendAll(res)
+      } while (totalAdded < PAGE_SIZE && this.hasMore)
       this._xIdle()
     } catch (e: any) {
       this._xIdle(e)
     }
   }
 
-  private _appendAll(res: GetSuggestions.Response) {
-    for (const item of res.data.actors) {
-      if (item.did === this.rootStore.me.did) {
-        continue // skip self
+  private async _appendAll(res: GetSuggestions.Response) {
+    this.loadMoreCursor = res.data.cursor
+    this.hasMore = !!this.loadMoreCursor
+    const newSuggestions = res.data.actors.filter(actor => {
+      if (actor.did === this.rootStore.me.did) {
+        return false // skip self
       }
-      if (item.myState?.follow) {
-        continue // skip already-followed users
+      if (actor.myState?.follow) {
+        return false // skip already-followed users
       }
-      this._append({
-        _reactKey: `item-${this.suggestions.length}`,
-        ...item,
+      return true
     })
-    }
-  }
-
-  private _append(item: SuggestedActor) {
-    this.suggestions.push(item)
+    this.suggestions = this.suggestions.concat(newSuggestions)
+    return newSuggestions.length
   }
 }

src/view/com/discover/SuggestedFollows.tsx

@@ -44,7 +44,7 @@ export const SuggestedFollows = observer(
 
     useEffect(() => {
       view
-        .setup()
+        .loadMore()
         .catch((err: any) =>
           store.log.error('Failed to fetch suggestions', err),
         )
@@ -56,12 +56,20 @@ export const SuggestedFollows = observer(
       }
     }, [view, view.isLoading, view.hasError, view.hasContent, onNoSuggestions])
 
-    const onPressTryAgain = () =>
+    const onRefresh = () => {
       view
-        .setup()
+        .refresh()
         .catch((err: any) =>
           store.log.error('Failed to fetch suggestions', err),
         )
+    }
+    const onEndReached = () => {
+      view
+        .loadMore()
+        .catch(err =>
+          view?.rootStore.log.error('Failed to load more suggestions', err),
+        )
+    }
 
     const onPressFollow = async (item: SuggestedActor) => {
       try {
@@ -108,16 +116,12 @@ export const SuggestedFollows = observer(
     }
     return (
       <View style={styles.container}>
-        {view.isLoading ? (
-          <View>
-            <ActivityIndicator />
-          </View>
-        ) : view.hasError ? (
+        {view.hasError ? (
           <ErrorScreen
             title="Failed to load suggestions"
             message="There was an error while trying to load suggested follows."
             details={view.error}
-            onPressTryAgain={onPressTryAgain}
+            onPressTryAgain={onRefresh}
           />
         ) : view.isEmpty ? (
           <View />
@@ -125,10 +129,19 @@ export const SuggestedFollows = observer(
           <View style={[styles.suggestionsContainer, pal.view]}>
             <FlatList
               data={view.suggestions}
-              keyExtractor={item => item._reactKey}
+              keyExtractor={item => item.did}
+              refreshing={view.isRefreshing}
+              onRefresh={onRefresh}
+              onEndReached={onEndReached}
               renderItem={renderItem}
-              style={s.flex1}
+              initialNumToRender={15}
+              ListFooterComponent={() => (
+                <View style={styles.footer}>
+                  {view.isLoading && <ActivityIndicator />}
+                </View>
+              )}
               contentContainerStyle={s.contentContainer}
+              style={s.flex1}
             />
           </View>
         )}
@@ -214,6 +227,10 @@ const styles = StyleSheet.create({
   suggestionsContainer: {
     flex: 1,
   },
+  footer: {
+    height: 200,
+    paddingTop: 20,
+  },
 
   actor: {
     borderTopWidth: 1,