finite_automaton_checker.py

def read_states():
    while True:
        try:
            num_states = int(input("- Number of states: "))
            if num_states < 1:
                print("Error: Number of states must be 1 or more.")
            else:
                states = [input(f"Enter the {i + 1} state: ") for i in range(num_states)]
                return states
        except ValueError:
            print("Error: Please enter a valid integer for the number of states.")


def read_inputs():
    while True:
        try:
            num_inputs = int(input("\n- Number of inputs: "))
            if num_inputs < 1:
                print("Error: Number of inputs must be 1 or more.")
            else:
                inputs = [input(f"Enter the {i + 1} input: ") for i in range(num_inputs)]
                return inputs
        except ValueError:
            print("Error: Please enter a valid integer for the number of inputs.")


def read_initial_state(states):
    while True:
        initial_state = input("\n- Enter the initial state: ")
        if initial_state in states:
            return initial_state
        else:
            print("Error: Initial state must be one of the entered states. Please try again.")


def read_final_states(states):
    while True:
        try:
            num_final_states = int(input("\n- Number of final states: "))
            if num_final_states < 1:
                print("Error: Number of final states must be 1 or more.")
            elif num_final_states > len(states):
                print("Error: Number of final states must be equal to or less than the number of states.")
            else:
                final_states = [input(f"Enter the {i + 1} final state: ") for i in range(num_final_states)]
                if all(state in states for state in final_states):
                    return final_states
                else:
                    print("Error: Final states must be among the entered states. Please try again.")
        except ValueError:
            print("Error: Please enter a valid integer for the number of final states.")


def read_fsm_table(states, inputs):
    fsm_table = {}
    for state in states:
        for inp in inputs:
            while True:
                next_state = input(f"{{ {state}, {inp} }} = ")
                if next_state in states:
                    fsm_table[(state, inp)] = next_state
                    break
                else:
                    print("Error: Next state must be one of the entered states. Please try again.")
    return fsm_table


def print_fsm_table(states, inputs, fsm_table):
    print(f"{'δ'} {'|'} {' '.join(inputs)}")
    print("-----------------------------------------")

    for state in states:
        print(f"{state} {'|'} {' '.join(fsm_table.get((state, inp)) for inp in inputs)}")


def read_string(initial_state, final_states, fsm_table):
    while True:
        user_input = input(
            "\nEnter a string or type 'exit' to stop the program or enter 'again' to run the program again: ")

        if user_input.lower() == 'exit':
            exit()
        elif user_input.lower() == 'again':
            break

        current_state = initial_state

        for char in user_input:
            next_state = fsm_table.get((current_state, char), None)
            if next_state:
                print(f"{current_state} -{char}-> {next_state}")
                current_state = next_state
            else:
                print(f"No transition for {current_state} -{char}->")
                break

        print(f"Final state/s: {', '.join(final_states)}")
        print(f"Current state: {current_state}")
        result = current_state in final_states
        if result:
            print(f"The string is accepted for the Finite Automaton.")
        else:
            print(f"The string is rejected for the Finite Automaton.")


if __name__ == "__main__":
    states = read_states()
    inputs = read_inputs()
    initial_state = read_initial_state(states)
    final_states = read_final_states(states)
    fsm_table = read_fsm_table(states, inputs)
    print_fsm_table(states, inputs, fsm_table)
    read_string(initial_state, final_states, fsm_table)