# Creating the getDetails function.
# Gets the username and opens the file of the username.
# If the file doesn't exit / username is invalid,
# An error message is shown.
def getDetails():
    # Makes the variable "username" global.
    # Can be accessed by other functions later.
    global username
    username = username_entry.get()
    try:
        usernameFile = open(username + ".txt", 'r+')
        usernameFileLine = usernameFile.readlines()
        # Gets the password the user input.
        password = password_entry.get()
        username_error.pack_forget()
        # Checks if the password is correct.
        # If not, an error message is shown.
        if password == usernameFileLine[0]:
            # Function to open the optionUI.
            optionMenu()
            # Closes the loginUI.
            loginUI.destroy()
        else:
            password_error.pack()
    # Checks if the username is invalid.
    except FileNotFoundError:
        # Packs the error message for invalid username.
        username_error.pack()


# Creates the main loginUI.
# Don't need a function for this.
loginUI = tkinter.Tk()
loginUI.title("loginUI")
loginUI.geometry("400x200")
loginUI.configure(background="#a1dbcd")
# Creating all the labels and entries for the loginUI.
blank_label = tkinter.Label(loginUI, text="", bg="#a1dbcd")
username_label = tkinter.Label(loginUI, text="USERNAME", font="Arial 8 bold", bg="#a1dbcd")
username_entry = tkinter.Entry(loginUI)
password_label = tkinter.Label(loginUI, text="PASSWORD", font="Arial 8 bold", bg="#a1dbcd")
password_entry = tkinter.Entry(loginUI, show="•")
username_error = tkinter.Label(loginUI, text="[ERROR] INVALID USERNAME", font="Arial 7 bold", fg="#ff0000", bg="#a1dbcd")
password_error = tkinter.Label(loginUI, text="[ERROR] INVALID PASSWORD", font="Arial 7 bold", fg="#ff0000", bg="#a1dbcd")
blank_label_two = tkinter.Label(loginUI, text="", bg="#a1dbcd")
loginUI_button = tkinter.Button(loginUI, text="LOGIN", bg="#d8dbfd", command=getDetails, width="5", font="Arial 11 bold")
# Packs all the labels and entries.
# Will be shown in the loginUI window.
blank_label.pack()
username_label.pack()
username_entry.pack()
password_label.pack()
password_entry.pack()
blank_label_two.pack()
loginUI_button.pack()
# Runs the loginUI
loginUI.mainloop()