From 28d0b8e13abf4abeb7238c48c0f6c927bfdbe3c6 Mon Sep 17 00:00:00 2001
From: Muthu Kumar <muthukumar@thefeathers.in>
Date: Fri, 1 Jun 2018 11:59:55 +0530
Subject: [PATCH] [Promise.object] initial implementation

* Resolves normal objects
* Resolves promises in objects
* Resolves nested promises
* Fails on circular objects with more than one ref to self
---
 index.js | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 index.js

diff --git a/index.js b/index.js
new file mode 100644
index 0000000..5b43d01
--- /dev/null
+++ b/index.js
@@ -0,0 +1,67 @@
+"use strict";
+
+const isObject = obj => obj && typeof obj === 'object' && obj.constructor === Object;
+
+const makeCircular = (obj, path) => {
+	const start = (o, p, i = 1) => {
+		if (i === path.length) return o[p[0]] = obj;
+		if (p.length > 0) {
+			o[p[0]] = {};
+			return start(o[p[0]], p.slice(1), i + 1);
+		} else return obj;
+	}
+	return start(obj, path);
+};
+
+const findPath = (obj, query) => {
+	return Object.keys(obj).reduce((acc, key) => {
+		const value = obj[key];
+		if (value === query) return [...acc, key];
+		if (isObject(value)) return [...acc, ...findPath(value)];
+		else return acc;
+	}, []);
+};
+
+// Resolves array
+const PromiseMap = (arr, functor) =>
+	Promise.all(arr.map(x => Promise.resolve(x).then(functor)));
+
+// Resolves objects
+const ResolveObject = obj =>
+	Promise.all(
+		Object.keys(obj).map(key =>
+			Promise.resolve(obj[key]).then(val => obj[key] = val))
+	)
+	.then(_ => obj);
+
+// Resolves recrusive deep objects
+const PromiseObject = parent => {
+	const ResolveDeepObject = object =>
+		Promise
+		.resolve(object)
+		.then(obj => {
+			if (Array.isArray(obj)) {
+				return PromiseMap(obj, obj => ResolveDeepObject(obj));
+			} else if (isObject(obj)) {
+				return ResolveObject(
+					Object
+					.keys(obj)
+					.reduce((acc, key) =>
+						(obj[key] === parent) ? {
+							...acc,
+							[key]: '[[ SELF ]]',
+						} : {
+							...acc,
+							[key]: ResolveDeepObject(obj[key]),
+						}, {}));
+			}
+			return obj;
+		});
+	return ResolveDeepObject(parent)
+		.then(obj => {
+			const path = findPath(obj, '[[ SELF ]]');
+			return path.length > 0 ? makeCircular(obj, path) : obj;
+		})
+};
+
+module.exports = PromiseObject;
\ No newline at end of file