Use promise cache to load remote thumbnails

1 files changed, 20 insertions, 2 deletions

diff --git a/server/helpers/promise-cache.ts b/server/helpers/promise-cache.ts
index 07e8a9962..303bab976 100644
--- a/server/helpers/promise-cache.ts
+++ b/server/helpers/promise-cache.ts
@@ -1,4 +1,4 @@
-export class PromiseCache <A, R> {
+export class CachePromiseFactory <A, R> {
   private readonly running = new Map<string, Promise<R>>()
 
   constructor (
@@ -8,14 +8,32 @@ export class PromiseCache <A, R> {
   }
 
   run (arg: A) {
+    return this.runWithContext(null, arg)
+  }
+
+  runWithContext (ctx: any, arg: A) {
     const key = this.keyBuilder(arg)
 
     if (this.running.has(key)) return this.running.get(key)
 
-    const p = this.fn(arg)
+    const p = this.fn.apply(ctx || this, [ arg ])
 
     this.running.set(key, p)
 
     return p.finally(() => this.running.delete(key))
   }
 }
+
+export function CachePromise (options: {
+  keyBuilder: (...args: any[]) => string
+}) {
+  return function (_target, _key, descriptor: PropertyDescriptor) {
+    const promiseCache = new CachePromiseFactory(descriptor.value, options.keyBuilder)
+
+    descriptor.value = function () {
+      if (arguments.length !== 1) throw new Error('Cache promise only support methods with 1 argument')
+
+      return promiseCache.runWithContext(this, arguments[0])
+    }
+  }
+}