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)