# Separate the line into 2 parts, split at the delimiter. Also strips the \n from the end of the line
def readAccount(line):
    return line.strip().split(":", 1)

# Try to find the account in the file
def findAccount(file, username):
  # Loop through each line ("account") in the file
  for line in file:
    # Separate the line into 2 parts, split at the ":" delimiter
    foundUsername, foundPassword = readAccount(line)

    # Comapre the usernames to see if they match
    if foundUsername == username:
      # If they match, return the username and password
      return [foundUsername, foundPassword]

  # If the account is not found, return None
  return None

def promptAndFindAccount():
  # Prompt the user to enter a username
  username = input("Enter a username: ")

  # Open the file in read mode to check if the username is already taken
  file = open("accounts.txt", "r")

  # Try to find the account
  account = findAccount(file, username)

  # We are done reading, close the file
  file.close()

  # Return the username and found account
  return username, account

def createAccount():
  # Try to find the account
  username, foundAccount = promptAndFindAccount()

  # If the account exists, print username already taken and return
  if foundAccount:
    print("Username already taken")
    return

  # The account doesn't already exist, so we can create it
  # Prompt the user to enter a password
  password = input("Enter a password: ")

  # Combine the username and password with a ":" delimiter
  account = username + ":" + password

  # Append the account to the file
  file = open("accounts.txt", "a")
  file.write(account + "\n")
  file.close()

  # Print success message
  print("Account created successfully")

def login():
  # Try to find the account
  username, existingAccount = promptAndFindAccount()

  # If the account doesn't exist, print login failed and try again
  if not existingAccount:
    print("Login failed. No account found.")
    return

  # Get the password from the account
  existingPassword = existingAccount[1]

  # If the account exists, compare passwords
  # Compare passwords
  password = input("Enter your password: ")

  # If the password is incorrect, print failed message and try again
  if password != existingPassword:
    print("Login failed. Incorrect password.")
    return

  # If the password is correct, print success message and return
  print("Login successful")

def showAccounts():
  # Open the file
  file = open("accounts.txt", "r")

  # Loop through each line and get the username and print it
  for line in file:
    username, _password = readAccount(line)
    print(f"Username: {username}")

  # We are done reading, close the file
  file.close()

def main():
  print("Welcome to the login system")

  while True:
    print ("--------------------------------")
    print("1. Create account")
    print("2. Login")
    print("3. Show accounts")
    print("4. Exit")

    # Prompt the user to enter a choice
    choice = input("Enter your choice: ")

    # If the choice is 1, create an account
    if choice == "1":
      createAccount()

    # If the choice is 2, login
    elif choice == "2":
      login()

    # If the choice is 3, show accounts
    elif choice == "3":
      showAccounts()

    # If the choice is 4, exit
    elif choice == "4":
      exit()

    # If the choice is invalid, print invalid choice and continue
    else:
      print("Invalid choice")

main()