# https://en.wikipedia.org/wiki/Deterministic_finite_automaton
class DFA: #Deterministic Finite Automaton

    def __init__ (self ,states : set , alphabets : set, transition_function , initial ,  accepted_states : set):

        self.states = states
        self.alphabets = alphabets

        if (self.__checkTransitionFunction__(transition_function)):
            self.transitionFunction = transition_function
        else :
            print ("Error: The Transition function has some errors")

        if (self.__checkInitialState__(initial)):
            self.initialState = initial
        else :
            print ("Error: The initial states in not in all valid states. Here states =", self.states)

        if (self.__checkAcceptedStates__(accepted_states)):
            self.acceptedStates = accepted_states
        else:
            print("Error: The accepted states are not in all valid states. Here states are =" , self.states)



    def __checkInitialState__ (self , initalState):
        return initalState in self.states

    def __checkAcceptedStates__ (self , accepted_states):
        return accepted_states.issubset(self.states)

    def __checkTransitionFunction__(self, transition_function):

        def checkKey(key):
            return len(key)==2 and key[0] in self.states and key[1] in self.alphabets

        if (set (transition_function.values()).issubset(self.states)):
            for key in transition_function :
                if not checkKey(key):
                    return False
            else:
                return True

    def getFinalState (self , inputData):
        currentState = self.initialState
        for input in inputData:
            if (input not in self.alphabets):
                print ("Input is not from the Alphabets")
                break
            currentState = self.transitionFunction.get((currentState, input) , None)
            if currentState == None:
                print("Error: The Transition Function do not have state for currentState: ", currentState , "input: ", input )
        return currentState

    def isAccepted (self , input):
        return self.getFinalState(input) in self.acceptedStates