Use the environment to configure session and skel defaults as well.
[wrw.git] / wrw / env.py
CommitLineData
e88ff533
FT
1import threading, weakref
2
3__all__ = ["environment", "root", "get", "binding", "var"]
4
5class stack(object):
6 __slots__ = ["env", "prev"]
7 def __init__(self, env, prev):
8 self.env = env
9 self.prev = prev
10
11class environment(object):
12 __slots__ = ["parent", "map"]
13 def __init__(self, parent = None):
14 self.parent = None
15 self.map = weakref.WeakKeyDictionary()
16
17 def get(self, var):
18 if var in self.map:
19 return self.map[var]
20 if self.parent is None:
21 return None
22 return self.parent.get(var)
23
24 def set(self, var, val):
25 self.map[var] = val
26
27 def __enter__(self):
28 cur = context.env
29 context.prev = stack(cur, context.prev)
30 context.env = self
31 return None
32
33 def __exit__(self, *excinfo):
34 prev = context.prev
35 if prev is None:
36 raise Exception("Unbalanced __enter__/__exit__")
37 context.env = prev.env
38 context.prev = prev.prev
39 return False
40
41root = environment()
42
43class context(threading.local):
44 env = root
45 prev = None
46context = context()
47
48def get():
49 return context.env
50
51class binding(object):
52 __slots__ = ["bindings"]
53 def __init__(self, bindings):
54 if isinstance(bindings, dict):
55 bindings = bindings.items()
56 self.bindings = bindings
57
58 def __enter__(self):
59 cur = context.env
60 new = environment(cur)
61 for var, val in self.bindings:
62 new.map[var] = val
63 context.prev = stack(cur, context.prev)
64 context.env = new
65 return None
66
67 def __exit__(self, *excinfo):
68 prev = context.prev
69 if prev is None:
70 raise Exception("Unbalanced __enter__/__exit__")
71 context.env = prev.env
72 context.prev = prev.prev
73 return False
74
75class var(object):
76 __slots__ = ["__weakref__"]
77 def __init__(self, default = None):
78 if default is not None:
79 root.map[self] = default
80
81 @property
82 def val(self):
83 return context.env.get(self)
84
85 def binding(self, val):
86 return binding([(self, val)])