1+ from collections import defaultdict
2+
3+ from app .log import log_err
4+
5+
6+ class Directory (object ):
7+ """ This class stores values and notifies callbacks which were registered to be executed as soon
8+ as some value is changed. This class works as DB cache mostly """
9+ def __init__ (self ):
10+ self .data = defaultdict (dict ) # storage. A key is a slot name, a value is a dictionary with data
11+ self .notify = defaultdict (lambda : defaultdict (list )) # registered callbacks: slot -> path -> handlers[]
12+
13+ @staticmethod
14+ def get_slot_name (db , table ):
15+ """ Convert db, table pair into a slot name """
16+ return db + "__" + table
17+
18+ def path_traverse (self , slot , path ):
19+ """
20+ Traverse a path in the storage.
21+ If the path is an empty string, it returns a value as it is.
22+ If the path is not an empty string, the method will traverse through the dictionary value.
23+ Example:
24+ self.data["key_1"] = { "abc": { "cde": { "fgh": "val_1", "ijk": "val_2" } } }
25+ self.path_traverse("key_1", "abc/cde") will return True, { "fgh": "val_1", "ijk": "val_2" }
26+ :param slot: storage key
27+ :param path: storage path as a string where each internal key is separated by '/'
28+ :return: a pair: True if the path was found, object if it was found
29+ """
30+ if slot not in self .data :
31+ return False , None
32+ elif path == '' :
33+ return True , self .data [slot ]
34+ d = self .data [slot ]
35+ for p in path .split ("/" ):
36+ if p not in d :
37+ return False , None
38+ d = d [p ]
39+ return True , d
40+
41+ def path_exist (self , db , table , path ):
42+ """
43+ Check if the path exists in the storage
44+ :param db: db name
45+ :param table: table name
46+ :param path: requested path
47+ :return: True if the path is available, False otherwise
48+ """
49+ slot = self .get_slot_name (db , table )
50+ return self .path_traverse (slot , path )[0 ]
51+
52+ def get_path (self , db , table , path ):
53+ """
54+ Return the requested path from the storage
55+ :param db: db name
56+ :param table: table name
57+ :param path: requested path
58+ :return: object if the path was found, None otherwise
59+ """
60+ slot = self .get_slot_name (db , table )
61+ return self .path_traverse (slot , path )[1 ]
62+
63+ def put (self , db , table , key , value ):
64+ """
65+ Put information into the storage. Notify handlers which are dependant to the information
66+ :param db: db name
67+ :param table: table name
68+ :param key: key to change
69+ :param value: value to put
70+ :return:
71+ """
72+ slot = self .get_slot_name (db , table )
73+ self .data [slot ][key ] = value
74+ if slot in self .notify :
75+ for path in self .notify [slot ].keys ():
76+ if self .path_exist (db , table , path ):
77+ for handler in self .notify [slot ][path ]:
78+ handler ()
79+
80+ def get (self , db , table , key ):
81+ """
82+ Get a value from the storage
83+ :param db: db name
84+ :param table: table name
85+ :param key: ket to get
86+ :return: value for the key
87+ """
88+ slot = self .get_slot_name (db , table )
89+ return self .data [slot ][key ]
90+
91+ def get_slot (self , db , table ):
92+ """
93+ Get an object from the storage
94+ :param db: db name
95+ :param table: table name
96+ :return: object for the slot
97+ """
98+ slot = self .get_slot_name (db , table )
99+ return self .data [slot ]
100+
101+ def remove (self , db , table , key ):
102+ """
103+ Remove a value from the storage
104+ :param db: db name
105+ :param table: table name
106+ :param key: key to remove
107+ """
108+ slot = self .get_slot_name (db , table )
109+ if slot in self .data :
110+ if key in self .data [slot ]:
111+ del self .data [slot ][key ]
112+ else :
113+ log_err ("Directory: Can't remove key '%s' from slot '%s'. The key doesn't exist" % (key , slot ))
114+ else :
115+ log_err ("Directory: Can't remove key '%s' from slot '%s'. The slot doesn't exist" % (key , slot ))
116+
117+ def remove_slot (self , db , table ):
118+ """
119+ Remove an object from the storage
120+ :param db: db name
121+ :param table: table name
122+ """
123+ slot = self .get_slot_name (db , table )
124+ if slot in self .data :
125+ del self .data [slot ]
126+ else :
127+ log_err ("Directory: Can't remove slot '%s'. The slot doesn't exist" % slot )
128+
129+ def available (self , db , table ):
130+ """
131+ Check if the table is available
132+ :param db: db name
133+ :param table: table name
134+ :return: True if the slot is available, False if not
135+ """
136+ slot = self .get_slot_name (db , table )
137+ return slot in self .data
138+
139+ def available_deps (self , deps ):
140+ """
141+ Check if all items from the deps list is available in the storage
142+ :param deps: list of dependencies
143+ :return: True if all dependencies are presented, False otherwise
144+ """
145+ res = True
146+ for db , table , path in deps :
147+ res = res and self .path_exist (db , table , path )
148+ return res
149+
150+ def subscribe (self , deps , handler ):
151+ """
152+ Subscribe the handler to be run as soon as all dependencies are presented
153+ :param deps:
154+ :param handler:
155+ :return:
156+ """
157+ for db , table , path in deps :
158+ slot = self .get_slot_name (db , table )
159+ self .notify [slot ][path ].append (handler )
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