use common/utils/singleton class for the stores

Signed-off-by: Roman <ixrock@gmail.com>

src/common/utils/singleton.ts

@@ -0,0 +1,27 @@
+/**
+ * Narrowing class instances to the one.
+ * Use "private" or "protected" modifier for constructor (when overriding) to disallow "new" usage.
+ *
+ * @example
+ *  const usersStore: UsersStore = UsersStore.getInstance();
+ */
+
+export class Singleton {
+  private static instances = new WeakMap<object, Singleton>();
+
+  // todo: figure out how to infer child class type + arguments
+  static getInstance<T extends Singleton>(...args: any[]): T {
+    if (!Singleton.instances.has(this)) {
+      Singleton.instances.set(this, Reflect.construct(this, args));
+    }
+    return Singleton.instances.get(this) as T;
+  }
+
+  static resetInstance() {
+    Singleton.instances.delete(this);
+  }
+
+  protected constructor() {
+    return this;
+  }
+}