from common.common import clear

def fin_01():
    """A shift code is where a message can be easily encoded and is one of the
        simplest codes to use. Each letter is moved forwards through the alphabet
        a set number of letters to be represented by a new letter. For instance,
        'abc' becomes 'bcd' when the code is shifted by one (i.e. each letter in
        the alphabet is moved forward one character). You need to create a
        program which will display the following menu:
                        1) Make a code
                        2) Decode a message
                        3) Quit

                        Enter your selection:
        If the user selects 1, they should be able to type in a message
        (including spaces) and then enter a number. Python should then display
        the encoded message once the shift code has been applied. If the user
        selects 2, they should enter an encoded message and the correct number
        and it should display the decoded message (i.e. move the correct number
        of letters backwards through the alphabet). If they select 3 it should
        stop the program from running. After they have encoded or decoded a
        message the menu should be displayed to them again until they select quit."""
    abc = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
           'n', 'ñ', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

    def code_msg(msg, steps):
        coded_message = ""
        for letter in msg:
            if letter in abc:
                ind = abc.index(letter)
                ind += steps
                while ind >= len(abc):
                    ind -= len(abc)
                coded_message += abc[ind]
            else:
                coded_message += letter
        print(coded_message)

    def decode_msg(msg, steps):
        decoded_message = ""
        for letter in msg:
            if letter in abc:
                ind = abc.index(letter)
                ind -= steps
                while ind < -len(abc):
                    ind += len(abc)
                decoded_message += abc[ind]
            else:
                decoded_message += letter
        print(decoded_message)

    while True:
        clear()
        print("""
        1) Codificar mensaje
        2) Decodificar mensaje
        s) Salir
        """)
        sel = input("Ingresa una opción: ")
        match sel:
            case '1':
                msg = input("Ingresa el mensaje a codificar: ")
                steps = int(input("Ingresa el nro. de pasos: "))
                code_msg(msg, steps)
                input("\nPresiona Enter para continuar\n")
            case '2':
                msg = input("Ingresa el mensaje a decodificar: ")
                steps = int(input("Ingresa el nro. de pasos: "))
                decode_msg(msg, steps)
                input("\nPresiona Enter para continuar\n")
            case 's':
                break
            case _:
                print("Debes ingresar una opción válida")
                input("\nPresiona Enter para continuar\n")