SimpleCache: allow specifying max items, add better type support

src/SimpleCache.ts

@@ -2,15 +2,19 @@ import Timeout = NodeJS.Timeout;
 
 const CLEAN_INTERVAL = 1000;
 
-export class SimpleCache {
+export class SimpleCache<T = any> {
-  protected readonly retentionTime;
+  protected readonly retentionTime: number;
+  protected readonly maxItems: number;
+
   protected cleanTimeout: Timeout;
   protected unloaded: boolean;
 
-  protected store: Map<string, { remove_at: number; value: any }>;
+  protected store: Map<string, { remove_at: number; value: T }>;
 
-  constructor(retentionTime) {
+  constructor(retentionTime: number, maxItems?: number) {
     this.retentionTime = retentionTime;
+    this.maxItems = maxItems;
+
     this.store = new Map();
   }
 
@@ -32,14 +36,19 @@ export class SimpleCache {
     }
   }
 
-  set(key: string, value) {
+  set(key: string, value: T) {
     this.store.set(key, {
       remove_at: Date.now() + this.retentionTime,
       value,
     });
+
+    if (this.maxItems && this.store.size > this.maxItems) {
+      const keyToDelete = this.store.keys().next().value;
+      this.store.delete(keyToDelete);
+    }
   }
 
-  get(key: string) {
+  get(key: string): T {
     const info = this.store.get(key);
     if (!info) return null;