src/codewars/kata_vigenere_cipher_helper.py

@@ -0,0 +1,40 @@
+class VigenereCipher(object):
+    def __init__(self, key, alphabet):
+        self.key = key
+        self.alphabet = alphabet
+
+    def encode(self, text):
+        encoded = []
+        idx_key = 0
+
+        for char in text:
+            if char in self.alphabet:
+                text_pos = self.alphabet.index(char)
+                key_char = self.key[idx_key % len(self.key)]
+                key_pos = self.alphabet.index(key_char)
+
+                pos = (text_pos + key_pos) % len(self.alphabet)
+                encoded.append(self.alphabet[pos])
+            else:
+                encoded.append(char)
+            idx_key += 1
+
+        return "".join(encoded)
+
+    def decode(self, text):
+        decoded = []
+        idx_key = 0
+
+        for char in text:
+            if char in self.alphabet:
+                text_pos = self.alphabet.index(char)
+                key_char = self.key[idx_key % len(self.key)]
+                key_pos = self.alphabet.index(key_char)
+
+                pos = (text_pos - key_pos) % len(self.alphabet)
+                decoded.append(self.alphabet[pos])
+            else:
+                decoded.append(char)
+            idx_key += 1
+
+        return "".join(decoded)