Add Future implementation

dist.js

@@ -6,6 +6,7 @@ module.exports = {
   ...require('./lib/datetime.js'),
   ...require('./lib/error.js'),
   ...require('./lib/events.js'),
+  ...require('./lib/future.js'),
   ...require('./lib/http.js'),
   ...require('./lib/objects.js'),
   ...require('./lib/pool.js'),

lib/future.js

@@ -0,0 +1,63 @@
+'use strict';
+
+class Future {
+  #executor;
+
+  constructor(executor) {
+    this.#executor = executor;
+  }
+
+  static of(value) {
+    return new Future((resolve) => resolve(value));
+  }
+
+  chain(fn) {
+    return new Future((resolve, reject) =>
+      this.fork(
+        (value) => fn(value).fork(resolve, reject),
+        (error) => reject(error),
+      ),
+    );
+  }
+
+  map(fn) {
+    return new Future((resolve, reject) =>
+      this.fork(
+        (value) =>
+          new Future((resolve, reject) => {
+            try {
+              resolve(fn(value));
+            } catch (error) {
+              reject(error);
+            }
+          }).fork(resolve, reject),
+        (error) => reject(error),
+      ),
+    );
+  }
+
+  fork(successed, failed) {
+    this.#executor(successed, failed);
+  }
+
+  promise() {
+    return new Promise((resolve, reject) => {
+      this.fork(
+        (value) => resolve(value),
+        (error) => reject(error),
+      );
+    });
+  }
+}
+
+const futurify =
+  (fn) =>
+  (...args) =>
+    new Future((resolve, reject) => {
+      fn(...args, (err, data) => {
+        if (err) reject(err);
+        else resolve(data);
+      });
+    });
+
+module.exports = { Future, futurify };

metautil.js

@@ -9,6 +9,7 @@ module.exports = {
   ...require('./lib/error.js'),
   ...require('./lib/events.js'),
   ...require('./lib/fs.js'),
+  ...require('./lib/future.js'),
   ...require('./lib/http.js'),
   ...require('./lib/network.js'),
   ...require('./lib/objects.js'),