src/mdis/walker.py

   1 __all__ = [
   2     "Walker",
   3     "WalkerMeta",
   4 ]
   5
   6 import enum
   7 import dataclasses
   8
   9 from . import dispatcher
  10
  11
  12 class WalkerMeta(dispatcher.DispatcherMeta):
  13     pass
  14
  15
  16 class PartId(enum.Enum):
  17     Index = enum.auto()
  18     Attribute = enum.auto()
  19     Hash = enum.auto()
  20
  21     def __call__(self, part):
  22         return {
  23             PartId.Index: "[{part}]",
  24             PartId.Attribute: ".{part}",
  25             PartId.Hash: "{{{part}}}",
  26         }[self].format(part=part)
  27
  28
  29 class Walker(dispatcher.Dispatcher, metaclass=WalkerMeta):
  30     @dispatcher.Hook(tuple, list)
  31     def dispatch_ordered_sequence(self, instance, path=()):
  32         for (index, item) in enumerate(instance):
  33             part = (PartId.Index, index)
  34             parts = (path + (part,))
  35             yield (item, parts)
  36             yield from self(item, path=parts)
  37
  38     @dispatcher.Hook(set, frozenset)
  39     def dispatch_unordered_sequence(self, instance, path=[]):
  40         for item in instance:
  41             part = (PartId.Hash, item)
  42             parts = (path + (part,))
  43             yield (item, parts)
  44             yield from self(item, path=parts)
  45
  46     @dispatcher.Hook(dataclasses.is_dataclass)
  47     def dispatch_dataclass(self, instance, path=[]):
  48         for field in dataclasses.fields(instance):
  49             key = field.name
  50             value = getattr(instance, key)
  51             part = (PartId.Attribute, key)
  52             parts = (path + (part,))
  53             yield (value, parts)
  54             yield from self(value, path=parts)
  55
  56     @dispatcher.Hook(dict)
  57     def dispatch_mapping(self, instance, path=[]):
  58         for (key, value) in instance.items():
  59             part = (PartId.Index, key)
  60             parts = (path + (part,))
  61             yield (value, parts)
  62             yield from self(value, path=parts)
  63
  64     @dispatcher.Hook(object)
  65     def dispatch_object(self, instance, path=()):
  66         yield from ()