From f1b267cc9fe7f6e5566dc2535b064b92aef92df1 Mon Sep 17 00:00:00 2001
From: Leonid Logvinov <logvinov.leon@gmail.com>
Date: Wed, 6 Dec 2017 20:55:09 +0300
Subject: Refactor web3Wrapper to a separate package

---
 packages/utils/src/promisify.ts | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 packages/utils/src/promisify.ts

(limited to 'packages/utils/src/promisify.ts')

diff --git a/packages/utils/src/promisify.ts b/packages/utils/src/promisify.ts
new file mode 100644
index 000000000..c114cf32f
--- /dev/null
+++ b/packages/utils/src/promisify.ts
@@ -0,0 +1,24 @@
+import * as _ from 'lodash';
+
+/**
+ * Transforms callback-based function -- func(arg1, arg2 .. argN, callback) -- into an ES6-compatible Promise.
+ * Promisify provides a default callback of the form (error, result) and rejects when `error` is not null. You can also
+ * supply thisArg object as the second argument which will be passed to `apply`.
+ */
+export function promisify<T>(
+    originalFn: (
+        ...args: any[],
+        // HACK: This can't be properly typed without variadic kinds https://github.com/Microsoft/TypeScript/issues/5453
+    ) => void,
+    thisArg?: any,
+): (...callArgs: any[]) => Promise<T> {
+    const promisifiedFunction = async (...callArgs: any[]): Promise<T> => {
+        return new Promise<T>((resolve, reject) => {
+            const callback = (err: Error|null, data?: T) => {
+                _.isNull(err) ? resolve(data) : reject(err);
+            };
+            originalFn.apply(thisArg, [...callArgs, callback]);
+        });
+    };
+    return promisifiedFunction;
+}
-- 
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