Update components retrival functions (#177)

Implemented comments from #169 for components.

Author: shsms

RELEASE_NOTES.md

@@ -7,6 +7,8 @@
 ## Upgrading
 
 * Change 'start_dt' and 'end_dt' to 'start_time' and 'end_time' respectively.
+* Rename 'list' to 'receive' in component data retrival functions
+* Return the receiver directly in '_recieve_microgrid_components_data_batch'
 
 ## New Features
 

src/frequenz/client/reporting/_batch_unroll_receiver.py

@@ -0,0 +1,74 @@
+# License: MIT
+# Copyright © 2024 Frequenz Energy-as-a-Service GmbH
+
+"""A receiver that unrolls batches of data into individual samples."""
+
+from collections.abc import Iterator
+
+from frequenz.channels import Receiver, ReceiverStoppedError
+from typing_extensions import override
+
+from ._types import ComponentsDataBatch, MetricSample, SensorsDataBatch
+
+
+class BatchUnrollReceiver(Receiver[MetricSample]):
+    """Receiver to unroll `ComponentsDataBatch`s into `MetricSample`s."""
+
+    def __init__(
+        self, stream: Receiver[ComponentsDataBatch | SensorsDataBatch]
+    ) -> None:
+        """Initialize the receiver.
+
+        Args:
+            stream: The stream to receive batches from.
+        """
+        self._stream: Receiver[ComponentsDataBatch | SensorsDataBatch] = stream
+        self._batch_iter: Iterator[MetricSample] | None = None
+        self._latest_sample: MetricSample | None = None
+        self._no_more_data: bool = False
+
+    @override
+    async def ready(self) -> bool:
+        """Wait until the next `MetricSample` is ready."""
+        # If ready is called multiple times, we should return the same result
+        # so we don't loose any data
+        if self._latest_sample is not None:
+            return True
+
+        while True:
+            # If we have a batch iterator, try to get the next sample
+            if self._batch_iter is not None:
+                try:
+                    self._latest_sample = next(self._batch_iter)
+                    return True
+                # If the batch is done, set the batch iterator to None
+                except StopIteration:
+                    self._batch_iter = None
+
+            # If we don't have a batch iterator, try to get the next batch
+            try:
+                batch = await anext(self._stream)
+                self._batch_iter = iter(batch)
+            # If the stream is done, return False
+            except StopAsyncIteration:
+                self._no_more_data = True
+                return False
+
+    @override
+    def consume(self) -> MetricSample:
+        """Consume the next `MetricSample`.
+
+        Returns:
+            The next `MetricSample`.
+
+        Raises:
+            ReceiverStoppedError: If the receiver is stopped.
+            RuntimeError: If the receiver is not ready.
+        """
+        sample = self._latest_sample
+        if sample is None:
+            if self._no_more_data:
+                raise ReceiverStoppedError(self)
+            raise RuntimeError("consume called before ready")
+        self._latest_sample = None
+        return sample