# 2 engines: NFA/DFA       RegEx-Art
# FA -> Finite Automation


class Regex:
    """
    Can only support a-z
    """
    def __init__(self):
        self.fsm = []

    def _char_to_int(self, char):
        """
        Returns 0 for a, 1 for b, 2 for c, ... 25 for z
        """
        return ord(char) - 97

    def create_state(self, default_value=0):
        return [default_value]*26

    def compile(self, regex_string):
        self.fsm = []
        # add state 0 as default failure state
        self.fsm.append(self.create_state())
        _iter = iter(regex_string)
        for char in _iter:
            next_valid_state = len(self.fsm) + 1
            if char == ".":
                state = self.create_state(next_valid_state)
                self.fsm.append(state)
            elif char == "[":
                state = self.create_state()
                while True:
                    try:
                        valid_char = next(_iter)
                        if valid_char == "]":
                            self.fsm.append(state)
                            break
                        else:
                            state[self._char_to_int(valid_char)] = next_valid_state
                    except StopIteration:
                        print("Invalid Regex: No ] found")
                        self.fsm = []
                        return
            else:
                state = self.create_state()
                state[self._char_to_int(char)] = next_valid_state
                self.fsm.append(state)

    def match(self, text):
        current_state = 1
        for input_char in text:
            current_state = self.fsm[current_state][self._char_to_int(input_char)]
            if current_state == 0:
                return False
        return current_state == len(self.fsm)


    def __str__(self):
        n = len(self.fsm)
        result = "    " + " ".join(str(x) for x in range(n)) + "\n"
        result += "----" + "--" * n + "\n"
        for number, row in enumerate(zip(*self.fsm), start=97):
            result += f"{chr(number)} | " + " ".join(str(x) for x in row) + "\n"
        return result

    __repr__ = __str__

r = Regex()
r.compile("abc")
print(r)