Refactor nip46

packages/lib/src/Deferred.ts

@@ -1,14 +1,27 @@
-export type Deferred<T> = Promise<T> & {
-  resolve: (arg: T) => void
-  reject: (arg: T) => void
+export type CustomPromise<T, E> = Promise<T> & {
+  __errorType: E
 }
 
-export const defer = <T>(): Deferred<T> => {
+export function makePromise<T, E>(
+  executor: (
+    resolve: (value: T | PromiseLike<T>) => void,
+    reject: (reason: E) => void
+  ) => void
+): CustomPromise<T, E> {
+  return new Promise(executor) as CustomPromise<T, E>
+}
+
+export type Deferred<T, E = T> = CustomPromise<T, E> & {
+  resolve: (arg: T) => void
+  reject: (arg: E) => void
+}
+
+export const defer = <T, E = T>(): Deferred<T, E> => {
   let resolve, reject
-  const p = new Promise((resolve_, reject_) => {
+  const p = makePromise((resolve_, reject_) => {
     resolve = resolve_
     reject = reject_
   })
 
-  return (Object.assign(p, {resolve, reject}) as unknown) as Deferred<T>
+  return (Object.assign(p, {resolve, reject}) as unknown) as Deferred<T, E>
 }