From 92a81a2290613f91471c6ba1e34f0a905eb1b049 Mon Sep 17 00:00:00 2001
From: Exortions <75327059+Exortions@users.noreply.github.com>
Date: Fri, 27 May 2022 08:58:45 -0700
Subject: [PATCH] merge: Add Twin Primes algorithm (#1024)

* Create TwinPrime.js

* Update TwinPrime.js

* Create TwinPrime.test.js

* Update TwinPrime.js

* Update TwinPrime.js

* Add suggestions

* Update TwinPrime.test.js

* Update TwinPrime.js

* Styling
---
 Maths/TwinPrime.js           | 29 +++++++++++++++++++++++++++++
 Maths/test/TwinPrime.test.js | 10 ++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 Maths/TwinPrime.js
 create mode 100644 Maths/test/TwinPrime.test.js

diff --git a/Maths/TwinPrime.js b/Maths/TwinPrime.js
new file mode 100644
index 000000000..871b1eab7
--- /dev/null
+++ b/Maths/TwinPrime.js
@@ -0,0 +1,29 @@
+import { PrimeCheck } from './PrimeCheck'
+
+/**
+ * @function twinPrime
+ * Gets the 'twin prime' of a prime number.
+ *
+ * @param {Integer} n The number to find the twin prime of.
+ * @returns {Integer} Either the twin, or -1 if n or n + 2 is not prime.
+ *
+ * @see https://en.wikipedia.org/wiki/Twin_prime
+ *
+ * @example twinPrime(5) = 7
+ * @example twinPrime(4) = -1
+*/
+function twinPrime (n) {
+  const prime = PrimeCheck(n)
+
+  if (!prime) {
+    return -1
+  }
+
+  if (!PrimeCheck(n + 2)) {
+    return -1
+  }
+
+  return n + 2
+}
+
+export { twinPrime }
diff --git a/Maths/test/TwinPrime.test.js b/Maths/test/TwinPrime.test.js
new file mode 100644
index 000000000..c3e057e10
--- /dev/null
+++ b/Maths/test/TwinPrime.test.js
@@ -0,0 +1,10 @@
+import { twinPrime } from '../TwinPrime.js'
+
+describe('Twin Primes', () => {
+  it('Should be valid twin primes', () => {
+    expect(twinPrime(3)).toBe(5)
+    expect(twinPrime(5)).toBe(7)
+    expect(twinPrime(4)).toBe(-1)
+    expect(twinPrime(17)).toBe(19)
+  })
+})