#!/usr/bin/env python3
"""
Utility to generate Caesar-shifted ciphertext for the challenge.
Usage: python3 generate_cipher.py --text "YOUR PLAINTEXT" --shift 3
"""
import argparse

ALPHA = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

def caesar_encrypt(text: str, shift: int) -> str:
    out = []
    for ch in text:
        if ch.isalpha():
            is_lower = ch.islower()
            base = ch.upper()
            idx = ALPHA.index(base)
            new_idx = (idx + shift) % 26
            new_ch = ALPHA[new_idx]
            out.append(new_ch.lower() if is_lower else new_ch)
        else:
            out.append(ch)
    return ''.join(out)

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('--text', required=True)
    parser.add_argument('--shift', type=int, default=3)
    args = parser.parse_args()
    print(caesar_encrypt(args.text, args.shift))