# standard imports
import enum

# local imports
from shep.error import (
        StateExists,
        StateInvalid,
        )


class State:

    def __init__(self, bits, logger=None, store=None):
        self.__bits = bits
        self.__limit = (1 << bits) - 1
        self.__c = 0
        self.__reverse = {}
        self.__logger = logger
        self.__store = store


    def __is_pure(self, v):
        c = 1
        for i in range(self.__bits):
            if c & v > 0:
                break
            c <<= 1
        return c == v


    def __check_name(self, k):
        if not k.isalpha():
            raise ValueError('only alpha')
        k = k.upper()
        try:
            getattr(self, k)
            raise StateExists(k)
        except AttributeError:
            pass
        return k


    def __check_valid(self, v):
        v = int(v)
        if self.__reverse.get(v):
            raise StateExists(v)
        return v


    def __check_value(self, v):
        v = self.__check_valid(v)
        if v > self.__limit:
            raise OverflowError(v)
        return v


    def __check_value_cursor(self, v):
        v = self.__check_valid(v)
        if v > 1 << self.__c:
            raise StateInvalid(v)
        return v


    def __set(self, k, v):
        setattr(self, k, v)
        self.__reverse[v] = k
        self.__c += 1


    def add(self, k):
        v = 1 << self.__c
        k = self.__check_name(k)
        v = self.__check_value(v)
        self.__set(k, v)
        

    def alias(self, k, v):
        k = self.__check_name(k)
        v = self.__check_value_cursor(v)
        if self.__is_pure(v):
            raise ValueError('use add to add pure values')
        self.__set(k, v)


    def all(self):
        l = []
        for k in dir(self):
            if k[0] == '_':
                continue
            if k.upper() != k:
                continue
            l.append(k)
        l.sort()
        return l


    def match(self, v, pure=False):
        r = []
        if not pure:
            m = self.__reverse.get(v)
            if m != None:
                r.append(m)
        c = 1
        for i in range(self.__bits):
            if v & c > 0:
                try:
                    k = self.__reverse[c]
                    r.append(k)
                except KeyError:
                    pass
            c <<= 1

        return r