From 514034d329262228f5eb79866f6429397fbd4e8d Mon Sep 17 00:00:00 2001
From: Kevin Ansfield <kevin@lookingsideways.co.uk>
Date: Thu, 28 May 2020 11:03:33 +0100
Subject: [PATCH] Fixed and improved members stats "debounced" fetches

no issue

- the "days changed" logic was incorrect so we were always performing new fetches rather than using existing data
- added a minor improvement that returns an in-progress fetch promise if we have one and params haven't changed - avoids triggering unnecessary extra fetches in the rare occasions the chart is re-rendered before a previous stats fetch has finished
---
 ghost/admin/app/services/members-stats.js | 34 +++++++++++++++--------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/ghost/admin/app/services/members-stats.js b/ghost/admin/app/services/members-stats.js
index be1d1481ab..bf524f783f 100644
--- a/ghost/admin/app/services/members-stats.js
+++ b/ghost/admin/app/services/members-stats.js
@@ -1,5 +1,6 @@
 import Service from '@ember/service';
 import {inject as service} from '@ember/service';
+import {task} from 'ember-concurrency-decorators';
 import {tracked} from '@glimmer/tracking';
 
 export default class MembersStatsService extends Service {
@@ -9,26 +10,35 @@ export default class MembersStatsService extends Service {
     @tracked stats = null;
 
     fetch({days}) {
-        // return existing stats unless data is > 1 min old
-        let daysChanged = days === this._days;
+        let daysChanged = days !== this._days;
         let staleData = this._lastFetched && this._lastFetched - new Date() > 1 * 60 * 1000;
+
+        // return an already in-progress promise unless params have changed
+        if (this._fetchTask.isRunning && !this._forceRefresh && !daysChanged) {
+            return this._fetchTask.last;
+        }
+
+        // return existing stats unless data is > 1 min old
         if (this.stats && !this._forceRefresh && !daysChanged && !staleData) {
             return Promise.resolve(this.stats);
         }
 
-        this._forceRefresh = false;
-        this._days = days;
-        this._lastFetched = new Date();
-
-        let statsUrl = this.ghostPaths.url.api('members/stats');
-
-        return this.ajax.request(statsUrl, {data: {days}}).then((stats) => {
-            this.stats = stats;
-            return stats;
-        });
+        return this._fetchTask.perform(...arguments);
     }
 
     invalidate() {
         this._forceRefresh = true;
     }
+
+    @task
+    *_fetchTask({days}) {
+        this._days = days;
+        this._lastFetched = new Date();
+        this._forceRefresh = false;
+
+        let statsUrl = this.ghostPaths.url.api('members/stats');
+        let stats = yield this.ajax.request(statsUrl, {data: {days}});
+        this.stats = stats;
+        return stats;
+    }
 }