feat: initial version

Author: gr2m

index.ts

@@ -0,0 +1,44 @@
+type ApiExtension = { [key: string]: any };
+type TestPlugin = (instance: Base) => ApiExtension | undefined;
+type Constructor<T> = new (...args: any[]) => T;
+
+/**
+ * @author https://stackoverflow.com/users/2887218/jcalz
+ * @see https://stackoverflow.com/a/50375286/10325032
+ */
+type UnionToIntersection<Union> = (Union extends any
+  ? (argument: Union) => void
+  : never) extends (argument: infer Intersection) => void // tslint:disable-line: no-unused
+  ? Intersection
+  : never;
+
+type AnyFunction = (...args: any) => any;
+
+type ReturnTypeOf<T extends AnyFunction | AnyFunction[]> = T extends AnyFunction
+  ? ReturnType<T>
+  : T extends AnyFunction[]
+  ? UnionToIntersection<ReturnType<T[number]>>
+  : never;
+
+export class Base {
+  static plugins: TestPlugin[] = [];
+  static plugin<T extends TestPlugin | TestPlugin[]>(plugin: T) {
+    const currentPlugins = this.plugins;
+
+    class NewTest extends this {
+      static plugins = currentPlugins.concat(plugin);
+    }
+
+    type Extension = ReturnTypeOf<T>;
+    return NewTest as typeof NewTest & Constructor<Extension>;
+  }
+
+  constructor() {
+    // apply plugins
+    // https://stackoverflow.com/a/16345172
+    const classConstructor = this.constructor as typeof Base;
+    classConstructor.plugins.forEach(plugin => {
+      Object.assign(this, plugin(this));
+    });
+  }
+}