1import re
 2from collections import OrderedDict
 3
 4class Santa:
 5    instance = None
 6    AGE_LIMIT = 5
 7    BAD_KID_GIFT = 'coal'
 8    presents = OrderedDict()
 9    childrens = {}
10    childrens_years = {}
11
12    def __new__(cls):
13        if not cls.instance:
14            cls.instance = super().__new__(cls)
15        return cls.instance
16
17    def __iter__(self):
18        for kid_id in self.childrens:
19            if self.presents.get(kid_id):
20                yield self.presents.get(kid_id)
21    
22    def add_child(self, child):
23        child_id = id(child)
24        self.childrens[child_id] = child
25        self.childrens_years[child_id] = 0        
26                 
27    def __call__(self, child, letter):
28        self.add_present(id(child), letter)
29             
30    def __matmul__(self, letter):
31        if not isinstance(letter, str):
32            raise TypeError
33        id_pattern = r'^\s*\d+\s*$'
34        child_id = re.search(id_pattern, letter, re.MULTILINE)
35        if child_id:
36            self.add_present(int(child_id.group()), letter)
37                
38    def add_present(self, child_id, letter):
39        wish_pattern = r'"([A-Za-z0-9 ]+)"|\'([A-Za-z0-9 ]+)\''
40        wish = re.search(wish_pattern, letter)
41        if wish:
42            wish_item = wish.group()[1:-1]
43            self.presents[child_id] = wish_item
44            
45    def xmas(self):
46        most_wanted_present = self.get_most_wanted()
47        if most_wanted_present == None:
48            for kid_id, kid in self.childrens.items():
49                self.childrens_years[kid_id] += 1
50        else:
51            for kid_id, kid in self.childrens.items():
52                self.childrens_years[kid_id] += 1
53                if self.childrens_years[kid_id] > self.AGE_LIMIT:
54                    continue
55                if self.presents.get(kid_id):
56                    if self.is_naughty(kid):
57                        kid(self.BAD_KID_GIFT)
58                    else:
59                        kid(self.presents[kid_id])
60                        del self.presents[kid_id]
61                else:
62                    if self.is_naughty(kid):
63                        kid(self.BAD_KID_GIFT)
64                    else:
65                        kid(most_wanted_present)
66        
67    def is_naughty(self, child):
68        return False
69    
70    def get_most_wanted(self):
71        all_presents = [present for present in self.presents.values()]
72        return max(all_presents, key=all_presents.count, default=None)
73            
74            
75class Kid(type):
76
77    def __new__(cls, name, bases, attr_dict):
78        if "__call__" not in attr_dict:
79            raise NotImplementedError("Kid class should implement __call__ method.")
80        return super().__new__(cls, name, bases, attr_dict)
81
82    def __call__(cls, *args, **kwargs):
83        instance = super().__call__(*args, **kwargs)
84        santa = Santa()
85        santa.add_child(instance)
86        return instance