# File:    validPassword.py
# Author:  Dr. Gibson
# Date:    2/22/2017
# Section: N/A
# E-mail:  k.gibson@umbc.edu 
# Description:
#   This file contains python code that asks the user to
#   enter a password, with specific requirements needed
#   in order for the password to be valid

MIN_LEN = 8      # minimum length of password
MAX_LEN = 20     # maximum length of password
BAD_CHAR1 = " "  # disallowed character #1
BAD_CHAR2 = "_"  # disallowed character #2

def main():

    #set up the boolean flag
    passwordValid = False
    
    # this will evaluate to True as long as the password is NOT valid
    while passwordValid == False:

        # get the password and assume (for now) that it's valid
        password = input("Please enter a password: ")
        passwordValid = True

        # if the password is too short, it's invalid
        if len(password) < MIN_LEN:
            print("Your password is too short.")
            passwordValid = False

        # if the password is too long, it's invalid
        if len(password) > MAX_LEN:
            print("Your password is too long.")
            passwordValid = False
            

        # to check for the disallowed characters, we need to iterate
        # over the entire list, by looking at each element (by index)
        place = 0
        while place < len(password):
            # if they have the first bad character (space), it's invalid
            if password[place] == BAD_CHAR1:
                print("You can't have any", BAD_CHAR1, "in your password")
                passwordValid = False
            # if they have the second bad character (underscore), it's invalid
            if password[place] == BAD_CHAR2:
                print("You can't have any", BAD_CHAR2, "in your password")
                passwordValid = False
            place += 1

        # if none of these if conditionals was true, then passwordValid
        # will still be True, and the while loop will exit

    # exited the while loop, so print out the chosen password
    print("Thanks for picking the super-secure password", password)

main()