Add cache interface, factory, and basic in-mem implementation

src/support/cache/MemoryCache.ts

@@ -0,0 +1,28 @@
+import {Collection} from "@extollo/util"
+import {Cache} from "./Cache"
+
+export class MemoryCache extends Cache {
+    private static cacheItems: Collection<{key: string, value: string}> = new Collection<{key: string; value: string}>()
+
+    public fetch(key: string): string | Promise<string | undefined> | undefined {
+        return MemoryCache.cacheItems
+            .firstWhere('key', '=', key)?.value
+    }
+
+    public put(key: string, value: string): void | Promise<void> {
+        const existing = MemoryCache.cacheItems.firstWhere('key', '=', key)
+        if ( existing ) {
+            existing.value = value
+        } else {
+            MemoryCache.cacheItems.push({ key, value })
+        }
+    }
+
+    public has(key: string): boolean | Promise<boolean> {
+        return !!MemoryCache.cacheItems.firstWhere('key', '=', key)
+    }
+
+    public drop(key: string): void | Promise<void> {
+        MemoryCache.cacheItems = MemoryCache.cacheItems.where('key', '!=', key)
+    }
+}