Merge pull request #87 from s-kostyuk/finalized_capabilities

Finalized capabilities (2/n)

This pull request added `_capability_name` field for public Capabilities and adds a `capabilities` property for all Things

dpl/dtos/thing_dto.py

@@ -18,7 +18,9 @@ class and a corresponding builder to be used to
     "is_available": True,
     # UNIX timestamp in float in UTC timezone, the time when
     # the Thing properties was last updated (changed)
-    "last_updated": 1517232368.30256
+    "last_updated": 1517232368.30256,
+    # indicates a list of supported Capabilities
+    "capabilities": ["actuator", "has_state", "is_active"]
 }
 ```
 
@@ -43,7 +45,8 @@ def build_thing_dto(thing: Thing) -> ThingDto:
         'id': thing.domain_id,
         'is_enabled': thing.is_enabled,
         'is_available': thing.is_available,
-        'last_updated': thing.last_updated
+        'last_updated': thing.last_updated,
+        'capabilities': thing.capabilities
     }
 
     result.update(thing.metadata)

dpl/things/capabilities/actuator.py

@@ -32,6 +32,8 @@ class Actuator(HasState):
     music and changing tracks, turning power on and off,
     turning light on and off and so on.
     """
+    _capability_name = 'actuator'
+
     @property
     def commands(self) -> Iterable[str]:
         """

dpl/things/capabilities/has_state.py

@@ -25,6 +25,8 @@ class HasState(IsActive):
     property, analyze an availability status in is_available property
     and so on).
     """
+    _capability_name = 'has_state'
+
     class States(Enum):
         """
         Possible states of the thing. Must be overridden in derived

dpl/things/capabilities/has_value.py

@@ -10,6 +10,8 @@ class HasValue(Generic[TValueType]):
     like the current temperature, humidity or brightness
     levels.
     """
+    _capability_name = 'has_value'
+
     @property
     def value(self) -> Optional[TValueType]:
         """

dpl/things/capabilities/is_active.py

@@ -27,6 +27,7 @@ class IsActive(object):
     property, analyze an availability status in is_available property
     and so on).
     """
+    _capability_name = 'is_active'
 
     @property
     def is_active(self) -> bool:

dpl/things/capabilities/on_off.py

@@ -14,6 +14,8 @@ class OnOff(object):
     is mapped to false. on command is also mapped to the activate and off
     command is mapped to the deactivate command.
     """
+    _capability_name = 'on_off'
+
     @property
     def is_powered_on(self) -> bool:
         """

dpl/things/capabilities/open_closed.py

@@ -22,6 +22,8 @@ class OpenClosed(HasState):
     opposite states (from ``open`` to ``closed``, from ``closed`` to ``open``,
     from ``opening`` to ``closed``, from ``closing`` to ``opened``).
     """
+    _capability_name = 'open_closed'
+
     class States(Enum):
         """
         Possible states of the thing: 'open', 'closed' and 'unknown'.

dpl/things/capability_filler_meta.py

@@ -0,0 +1,47 @@
+"""
+This class contains a definition of the CapabilityFiller metaclass.
+"""
+import inspect
+from typing import Iterable, Generator
+
+
+class CapabilityFiller(type):
+    """
+    CapabilityFiller is a metaclass which intercepts the class
+    creation process, discovers all Capabilities (parent classes)
+    of the class and fills the corresponding ``_capabilities``
+    private property of the class with the names of all Capabilities
+    which was implemented by the class
+    """
+
+    def __new__(mcs, name, bases, class_dict):
+        cls = type.__new__(mcs, name, bases, class_dict)
+
+        mros = inspect.getmro(cls)
+
+        cls._capabilities = tuple(
+            mcs._capability_list_generator(source=mros)
+        )
+
+        return cls
+
+    @staticmethod
+    def _capability_list_generator(source: Iterable) -> Generator[str, None, None]:
+        """
+        A generator which extracts capability names from the
+        specified list of Capabilities
+
+        :param source: a list of parent classes to be parsed
+        :return: a generator of Capability names
+        """
+        attr = '_capability_name'
+
+        for i in source:
+            if attr not in i.__dict__:
+                continue
+
+            name = getattr(i, attr, None)
+
+            assert name is not None
+
+            yield name

dpl/things/thing.py

@@ -2,7 +2,7 @@
 import time
 from copy import deepcopy
 from types import MappingProxyType
-from collections import Mapping
+from typing import Mapping, Sequence
 
 # Include 3rd-party modules
 # Include DPL modules
@@ -12,9 +12,11 @@
 from dpl.things.capabilities.is_enabled import IsEnabled
 from dpl.things.capabilities.is_available import Available
 from dpl.things.capabilities.last_updated import LastUpdated
+from .capability_filler_meta import CapabilityFiller
 
 
-class Thing(BaseEntity, IsEnabled, Available, LastUpdated):
+class Thing(BaseEntity, IsEnabled, Available, LastUpdated,
+            metaclass=CapabilityFiller):
     """
     Thing is a base class for all connected devices in the system.
 
@@ -52,6 +54,8 @@ class Thing(BaseEntity, IsEnabled, Available, LastUpdated):
     like 'current_track', 'play' and 'stop' for player. Or 'on'/'off' for
     lighting, etc.
     """
+    # _capabilities field will be filled by the CapabilityFiller metaclass
+    _capabilities = None   # type: Sequence[str]
 
     def __init__(
             self, domain_id: TDomainId,
@@ -76,6 +80,16 @@ def __init__(
         self._last_updated = time.time()
         self._is_enabled = False
 
+    @property
+    def capabilities(self) -> Sequence[str]:  # -> Collection[str]:
+        """
+        Returns a list of Capabilities supported by this Thing
+
+        :return: a collection of Capability names supported by
+                 (implemented by) this Thing
+        """
+        return self._capabilities
+
     @property
     def metadata(self) -> Mapping:
         """