Improve usage module, consolidate API with emeter (#249)

* Consolidate API for both emeter&usage modules
* Add new cli command 'usage' to query usage

kasa/modules/emeter.py

@@ -1,4 +1,7 @@
 """Implementation of the emeter module."""
+from datetime import datetime
+from typing import Dict, Optional
+
 from ..emeterstatus import EmeterStatus
 from .usage import Usage
 
@@ -6,15 +9,61 @@ from .usage import Usage
 class Emeter(Usage):
     """Emeter module."""
 
-    def query(self):
-        """Prepare query for emeter data."""
-        return self._device._create_emeter_request()
-
     @property  # type: ignore
     def realtime(self) -> EmeterStatus:
         """Return current energy readings."""
         return EmeterStatus(self.data["get_realtime"])
 
+    @property
+    def emeter_today(self) -> Optional[float]:
+        """Return today's energy consumption in kWh."""
+        raw_data = self.daily_data
+        today = datetime.now().day
+        data = self._emeter_convert_emeter_data(raw_data)
+
+        return data.get(today)
+
+    @property
+    def emeter_this_month(self) -> Optional[float]:
+        """Return this month's energy consumption in kWh."""
+        raw_data = self.monthly_data
+        current_month = datetime.now().month
+        data = self._emeter_convert_emeter_data(raw_data)
+
+        return data.get(current_month)
+
     async def erase_stats(self):
-        """Erase all stats."""
+        """Erase all stats.
+
+        Uses different query than usage meter.
+        """
         return await self.call("erase_emeter_stat")
+
+    async def get_daystat(self, *, year, month, kwh=True):
+        """Return daily stats for the given year & month."""
+        raw_data = await super().get_daystat(year=year, month=month)
+        return self._emeter_convert_emeter_data(raw_data["day_list"], kwh)
+
+    async def get_monthstat(self, *, year, kwh=True):
+        """Return monthly stats for the given year."""
+        raw_data = await super().get_monthstat(year=year)
+        return self._emeter_convert_emeter_data(raw_data["month_list"], kwh)
+
+    def _emeter_convert_emeter_data(self, data, kwh=True) -> Dict:
+        """Return emeter information keyed with the day/month.."""
+        response = [EmeterStatus(**x) for x in data]
+
+        if not response:
+            return {}
+
+        energy_key = "energy_wh"
+        if kwh:
+            energy_key = "energy"
+
+        entry_key = "month"
+        if "day" in response[0]:
+            entry_key = "day"
+
+        data = {entry[entry_key]: entry[energy_key] for entry in response}
+
+        return data