From 253421fee90fea1f6bb06167f5ec4fbba787a187 Mon Sep 17 00:00:00 2001
From: divlo <contact@divlo.fr>
Date: Wed, 21 Oct 2020 11:30:48 +0200
Subject: [PATCH] feat(solution): add typescript-caesar-cipher

---
 .../typescript-caesar-cipher/README.md        |  5 +++
 .../typescript-caesar-cipher/solution.ts      | 42 +++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 challenges/caesar-cipher/solutions/typescript-caesar-cipher/README.md
 create mode 100644 challenges/caesar-cipher/solutions/typescript-caesar-cipher/solution.ts

diff --git a/challenges/caesar-cipher/solutions/typescript-caesar-cipher/README.md b/challenges/caesar-cipher/solutions/typescript-caesar-cipher/README.md
new file mode 100644
index 0000000..7698fae
--- /dev/null
+++ b/challenges/caesar-cipher/solutions/typescript-caesar-cipher/README.md
@@ -0,0 +1,5 @@
+# typescript-caesar-cipher - caesar-cipher
+
+Programming language : TypeScript
+
+Created by [@Divlo](https://github.com/Divlo) on 21 October 2020.
diff --git a/challenges/caesar-cipher/solutions/typescript-caesar-cipher/solution.ts b/challenges/caesar-cipher/solutions/typescript-caesar-cipher/solution.ts
new file mode 100644
index 0000000..a8a0a41
--- /dev/null
+++ b/challenges/caesar-cipher/solutions/typescript-caesar-cipher/solution.ts
@@ -0,0 +1,42 @@
+const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('')
+
+interface ShiftedLetter {
+  origin: string
+  shifted: string
+}
+
+function shiftAlphabet (shift: number): ShiftedLetter[] {
+  const result: ShiftedLetter[] = []
+  for (let index = 0; index < alphabet.length; index++) {
+    const letter = alphabet[index]
+    let shiftedIndex = index + shift
+    if (shiftedIndex > alphabet.length - 1) {
+      shiftedIndex = Math.abs(alphabet.length - shiftedIndex)
+    }
+    result.push({
+      origin: letter,
+      shifted: alphabet[shiftedIndex]
+    })
+  }
+  return result
+}
+
+function solution (str: string, shift: number): string {
+  const shiftedAlphabet = shiftAlphabet(shift)
+  let result = ''
+  for (const letter of str) {
+    if (letter === ' ') {
+      result += ' '
+    } else {
+      for (const { origin, shifted } of shiftedAlphabet) {
+        if (letter === shifted) {
+          result += origin
+          break
+        }
+      }
+    }
+  }
+  return result
+}
+
+export default solution