Add metric calcuator for BatteryPool

MetricCalculator defines what components and metrics are needed
to compute high level metrics and how to calculate it.

Signed-off-by: ela-kotulska-frequenz <[email protected]>

Author: ela-kotulska-frequenz

src/frequenz/sdk/timeseries/battery_pool/_component_metrics.py

@@ -0,0 +1,83 @@
+# License: MIT
+# Copyright © 2023 Frequenz Energy-as-a-Service GmbH
+
+"""Class that stores values of the component metrics."""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from datetime import datetime
+
+from ...microgrid.component import ComponentMetricId
+
+
+class ComponentMetricsData:
+    """Store values of the component metrics."""
+
+    def __init__(
+        self,
+        component_id: int,
+        timestamp: datetime,
+        metrics: Mapping[ComponentMetricId, float],
+    ) -> None:
+        """Create class instance.
+
+        Args:
+            component_id: component id
+            timestamp: timestamp the same for all metrics
+            metrics: map between metrics and its values.
+        """
+        self._component_id = component_id
+        self._timestamp = timestamp
+        self._metrics: Mapping[ComponentMetricId, float] = metrics
+
+    @property
+    def component_id(self) -> int:
+        """Get component id of the given metrics.
+
+        Returns:
+            Component id
+        """
+        return self._component_id
+
+    @property
+    def timestamp(self) -> datetime:
+        """Get timestamp of the given metrics.
+
+        Returns:
+            Timestamp (one for all metrics).
+        """
+        return self._timestamp
+
+    def get(self, metric: ComponentMetricId) -> float | None:
+        """Get metric value.
+
+        Args:
+            metric: metric id
+
+        Raises:
+            KeyError: If given metric is not stored in the object.
+
+        Returns:
+            Value of the metric.
+        """
+        return self._metrics.get(metric, None)
+
+    def __eq__(self, other: object) -> bool:
+        """Compare two objects of this class.
+
+        Object are considered as equal if all stored values except for timestamp
+        are equal.
+
+        Args:
+            other: object to compare.
+
+        Returns:
+            True if two objects are equal, false otherwise.
+        """
+        if not isinstance(other, ComponentMetricsData):
+            return False
+
+        return (
+            self.component_id == other.component_id and self._metrics == other._metrics
+        )