refactor

src/utils.ts

@@ -70,30 +70,6 @@ export function reverseAsyncComparer<T>(comparer: MaybeAsyncComparer<T>): AsyncC
   return async (a, b) => await comparer(b, a);
 }
 
-export function* asGenerator<T>(iterator: Iterator<T>) {
-  while (true) {
-    const next = iterator.next();
-
-    if (next.done) {
-      return next.value;
-    }
-
-    yield next.value;
-  }
-}
-
-export async function* asAsyncGenerator<T>(iterator: MaybeAsyncIterator<T>) {
-  while (true) {
-    const next = await iterator.next();
-
-    if (next.done) {
-      return next.value;
-    }
-
-    yield next.value;
-  }
-}
-
 export function asArray<T>(iterable: Iterable<T>) {
   return Array.isArray(iterable) ? <T[]>iterable : Array.from(iterable);
 }
@@ -110,6 +86,44 @@ class WrappedIterator<T> implements Iterable<T> {
   }
 }
 
-export function wrapAsIterable<T>(iterator: Iterator<T>): Iterable<T> {
+export function asIterable<T>(iterator: Iterator<T>): Iterable<T> {
   return isIterable<T>(iterator) ? iterator : new WrappedIterator(iterator);
 }
+
+class WrappedAsyncIterator<T> implements AsyncIterable<T> {
+  readonly #iterator: AsyncIterator<T>;
+
+  constructor(iterator: AsyncIterator<T>) {
+    this.#iterator = iterator;
+  }
+
+  [Symbol.asyncIterator]() {
+    return this.#iterator;
+  }
+}
+
+export function asAsyncIterable<T>(iterator: AsyncIterator<T>): AsyncIterable<T> {
+  return isAsyncIterable<T>(iterator) ? iterator : new WrappedAsyncIterator(iterator);
+}
+
+const _emptyIterableIterator = new class EmptyIterableIterator implements IterableIterator<any> {
+  [Symbol.iterator]() {
+    return this;
+  }
+
+  next(): IteratorResult<any, any> {
+    return { done: true, value: undefined };
+  }
+
+  return(value?: any): IteratorResult<any, any> {
+    throw new Error("Method not implemented.");
+  }
+
+  throw(e?: any): IteratorResult<any, any> {
+    throw new Error("Method not implemented.");
+  }
+}
+
+export function emptyIterableIterator<T>(): IterableIterator<T> {
+  return _emptyIterableIterator;
+}