From 457f1ee53ebd011bce3e41e34dd2be885a1ac3ec Mon Sep 17 00:00:00 2001
From: Matei Adriel <rafaeladriel11@gmail.com>
Date: Thu, 26 Dec 2019 17:05:16 +0200
Subject: [PATCH] typescript(option): feat: added the 'combine' helper

Signed-off-by: prescientmoon <git@moonythm.dev>
---
 typescript/option/src/helpers/combine.test.ts | 26 +++++++++++++++++++
 typescript/option/src/helpers/combine.ts      | 19 ++++++++++++++
 typescript/option/src/helpers/external.ts     |  3 ++-
 3 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 typescript/option/src/helpers/combine.test.ts
 create mode 100644 typescript/option/src/helpers/combine.ts

diff --git a/typescript/option/src/helpers/combine.test.ts b/typescript/option/src/helpers/combine.test.ts
new file mode 100644
index 0000000..cd96495
--- /dev/null
+++ b/typescript/option/src/helpers/combine.test.ts
@@ -0,0 +1,26 @@
+import { expect } from 'chai'
+import { combine } from './combine'
+import { someX } from '../../test/constants'
+import { None } from '../types'
+import { isSome } from './isSome'
+
+describe('The combine helepr', () => {
+    it('should return None if the iterable contains any Nones', () => {
+        // act
+        const result = combine([someX, someX, None, someX, someX])
+
+        // assert
+        expect(result).to.equal(None)
+    })
+
+    it("should return Some when the iterable doesn't contain any None", () => {
+        // arrange
+        const items = Array(50).fill(someX)
+
+        // act
+        const result = combine(items)
+
+        // act
+        expect(isSome(result)).to.be.true
+    })
+})
diff --git a/typescript/option/src/helpers/combine.ts b/typescript/option/src/helpers/combine.ts
new file mode 100644
index 0000000..b922a57
--- /dev/null
+++ b/typescript/option/src/helpers/combine.ts
@@ -0,0 +1,19 @@
+import { Option, None, Some } from '../types'
+import { isNone } from './isNone'
+
+/**
+ * If every Option in the list is present, return all of the values unwrapped.
+ * If there are any Nones, the whole function fails and returns None.
+ *
+ * @param iterable The iterable to combine.
+ */
+export const combine = <T>(iterable: Iterable<Option<T>>) => {
+    const set = new Set(iterable)
+
+    if (set.has(None)) {
+        return None
+    }
+
+    const array = Array.from(set) as T[]
+    return array as Option<T[]>
+}
diff --git a/typescript/option/src/helpers/external.ts b/typescript/option/src/helpers/external.ts
index 9cddd76..a992f59 100644
--- a/typescript/option/src/helpers/external.ts
+++ b/typescript/option/src/helpers/external.ts
@@ -1,5 +1,6 @@
 export * from './bind'
 export * from './bindAsync'
+export * from './combine'
 export * from './count'
 export * from './exists'
 export * from './filter'
@@ -24,6 +25,6 @@ export * from './toArray'
 export * from './toNullable'
 export * from './unpack'
 export * from './unwrap'
+export * from './values'
 export * from './withDefault'
 export * from './withDefaultLazy'
-export * from './values'