added Binary Sensor Thing

Author: alexbarcelo

src/ham/binary_sensor.py

@@ -0,0 +1,45 @@
+import logging
+
+from .things import Thing
+
+logger = logging.getLogger(__name__)
+
+
+class BinarySensor(Thing):
+    """Basic class for a Binary Sensor entity.
+    
+    Binary Sensors are things that only publish an ON or OFF state.
+
+    This is implemented in this library through a write-only property, called
+    `state`. Other Sensor subclasses may reimplement them; the responsible of
+    publishing stuff is the Thing.publish_state method.
+    """
+    device_class: str
+    enabled_by_default: bool
+    encoding: str
+    entity_category: str
+    expire_after: int
+    force_update: bool
+    icon: str
+
+    config_fields = [
+        "device_class", "enabled_by_default", "encoding", "entity_category",
+        "expire_after", "force_update", "icon"
+    ]
+
+    @property
+    def component(self):
+        return "binary_sensor"
+
+    @property
+    def state(self):
+        raise AttributeError("Canonical implementation of binary_sensor has a write-only state")
+
+    @state.setter
+    def state(self, value: bool):
+        self.publish_state(value)
+
+    def get_config(self):
+        config = super().get_config()
+        config["state_topic"] = f'~/{ self.short_id }/main'
+        return config