def encode(plaintext: str, key: str) -> str:
    table = generate_table(key)
    plaintext = prepare_input(plaintext)
    ciphertext = ""

    # https://en.wikipedia.org/wiki/Playfair_cipher#Description
    for char1, char2 in chunker(plaintext, 2):
        row1, col1 = divmod(table.index(char1), 5)
        row2, col2 = divmod(table.index(char2), 5)

        if row1 == row2:
            ciphertext += table[row1 * 5 + (col1 + 1) % 5]
            ciphertext += table[row2 * 5 + (col2 + 1) % 5]
        elif col1 == col2:
            ciphertext += table[((row1 + 1) % 5) * 5 + col1]
            ciphertext += table[((row2 + 1) % 5) * 5 + col2]
        else:  # rectangle
            ciphertext += table[row1 * 5 + col2]
            ciphertext += table[row2 * 5 + col1]

    return ciphertext