1import re
  2
  3class SingletonType(type):
  4    def __new__(mcs, name, bases, attrs):
  5        def singleton_new(cls):
  6            if not hasattr(cls, 'instance'):
  7                cls.instance = object.__new__(cls)
  8            return cls.instance
  9        attrs['__new__'] = singleton_new
 10        return type.__new__(mcs, name, bases, attrs)
 11
 12
 13class Santa(metaclass = SingletonType):
 14    """A class for greedy kids."""
 15    all_kids = set()
 16    kids_objects = {}
 17    kids_ages = {}
 18    gifts = {}
 19    naughty_kids = set()
 20
 21    def extract_gift(self, letter: str):
 22        """Extracts a gift from a letter or call."""
 23        pattern_gift = r'(?:\")([A-Za-z0-9]+[A-Za-z0-9 ]*)(?:\")|(?:\')([A-Za-z0-9]+[A-Za-z0-9 ]*)(?:\')'
 24        pattern = re.compile(pattern_gift, re.MULTILINE)
 25        gifts = pattern.findall(letter)
 26
 27        for gift_tuple in reversed(gifts):
 28            for gift in gift_tuple:
 29                if gift:
 30                    return gift
 31        return None
 32
 33    def extract_signature_from_letter(self, letter: str):
 34        """Extracts a signiture from a letter."""
 35        pattern_signature = r'\s*(\d+)\s*'
 36        pattern = re.compile(pattern_signature, re.MULTILINE)
 37        signature = pattern.findall(letter)
 38        if signature:
 39            return signature[-1]
 40        return None
 41
 42    def __matmul__(self, letter: str):
 43        """Predefined operator @ when a kid writes a letter to Santa."""
 44        gift = self.extract_gift(letter)
 45        signature = self.extract_signature_from_letter(letter)
 46
 47        index = int(signature)
 48        self.gifts[index] = gift
 49        self.all_kids.add(index)
 50        self.kids_ages[index] = 0
 51        if id(signature) in self.kids_objects:
 52            self.kids_objects[signature] = signature
 53
 54    def __call__(self, child, wish: str):
 55        """Predefined operator () when a kid calls Santa."""
 56        index = id(child)
 57        self.gifts[index] = self.extract_gift(wish)
 58
 59    def __iter__(self):
 60        return iter(self.gifts.values())
 61
 62    def get_most_wanted_gift_this_year(self):
 63        """Calculates what is the most wanted gift this year."""
 64        this_years_gifts = [gift for gift in self.gifts.values() if gift is not None]
 65
 66        if set(this_years_gifts):
 67            most_wanted_gift_this_year = max(set(this_years_gifts) , key = this_years_gifts.count)
 68        else:
 69            most_wanted_gift_this_year = None
 70        return most_wanted_gift_this_year
 71
 72    def remove_kid(self, keys_to_delete):
 73        """Deletes kid because it is too old for presents."""
 74        for key in keys_to_delete:
 75            del self.gifts[key]
 76            del self.kids_ages[key]
 77            del self.kids_objects[key]
 78            self.all_kids.remove(key)
 79
 80    def mark_as_naughty(self, kid):
 81        """Marks a kid as naughty."""
 82        if id(kid) in self.all_kids:
 83            self.naughty_kids.add(id(kid))
 84
 85    def xmas(self):
 86        """Time for presents."""
 87        for key in self.kids_ages:
 88            self.kids_ages[key] += 1
 89
 90        most_wanted_gift = self.get_most_wanted_gift_this_year()
 91        keys_to_delete = []
 92
 93        for kid, age in self.kids_ages.items():
 94            cur_gift = self.gifts[kid]
 95            if age > 5:
 96                keys_to_delete.append(kid)
 97                continue
 98            elif age <= 5:
 99                kid_obj = self.kids_objects.get(kid)
100                if all(value == None for value in self.gifts.values()):
101                    break
102                elif kid in self.naughty_kids:
103                    kid_obj("coal")
104                elif cur_gift is None:
105                    kid_obj(most_wanted_gift)
106                else:
107                    kid_obj(cur_gift)
108
109        for cur_gift in self.gifts:
110            self.gifts[cur_gift] = None
111
112        self.remove_kid(keys_to_delete)
113        self.naughty_kids.clear()
114
115
116def detect_naughty_kid(func):
117    """Checks if the kid is naughty."""
118    def wrapper(self, *args, **kwargs):
119        try:
120            return func(self, *args, **kwargs)
121        except Exception:
122            Santa().mark_as_naughty(self)
123            raise
124    return wrapper
125
126
127class Kid(type):
128    """A class that defines a kid."""
129    def __new__(mcs, name, bases, attrs):
130        if '__call__' not in attrs:
131            raise NotImplementedError("Sorry, you should implement the __call__ method of the kid :).")
132        for key, value in attrs.items():
133            if callable(value) and not key.startswith("_"):
134                attrs[key] = detect_naughty_kid(value)
135        return super().__new__(mcs, name, bases, attrs)
136
137    def __call__(cls, *args, **kwargs):
138        instance = super().__call__(*args, **kwargs)
139        if id(instance) not in Santa().all_kids:
140            Santa().all_kids.add(id(instance))
141            Santa().gifts[id(instance)] = None
142            Santa().kids_ages[id(instance)] = 0
143            Santa().kids_objects[id(instance)] = instance
144        return instance