Add a RelaySender implementation

Signed-off-by: Sahas Subramanian <sahas.subramanian@proton.me>

Author: shsms

src/frequenz/channels/experimental/__init__.py

@@ -10,3 +10,9 @@
 """
 
 from ._pipe import Pipe
+from ._relay_sender import RelaySender
+
+__all__ = [
+    "Pipe",
+    "RelaySender",
+]

src/frequenz/channels/experimental/_relay_sender.py

@@ -0,0 +1,56 @@
+# License: MIT
+# Copyright © 2024 Frequenz Energy-as-a-Service GmbH
+
+"""A Sender for sending messages to multiple senders.
+
+The `RelaySender` class takes multiple senders and forwards all the messages sent to it,
+to the senders it was created with.
+"""
+
+import typing
+
+from .._generic import SenderMessageT_contra
+from .._sender import Sender
+
+
+class RelaySender(typing.Generic[SenderMessageT_contra], Sender[SenderMessageT_contra]):
+    """A Sender for sending messages to multiple senders.
+
+    The `RelaySender` class takes multiple senders and forwards all the messages sent to
+    it, to the senders it was created with.
+
+    Example:
+        ```python
+        from frequenz.channels import Broadcast
+        from frequenz.channels.experimental import RelaySender
+
+        channel1: Broadcast[int] = Broadcast(name="channel1")
+        channel2: Broadcast[int] = Broadcast(name="channel2")
+
+        receiver1 = channel1.new_receiver()
+        receiver2 = channel2.new_receiver()
+
+        tee_sender = RelaySender(channel1.new_sender(), channel2.new_sender())
+
+        await tee_sender.send(5)
+        assert await receiver1.receive() == 5
+        assert await receiver2.receive() == 5
+        ```
+    """
+
+    def __init__(self, *senders: Sender[SenderMessageT_contra]) -> None:
+        """Create a new RelaySender.
+
+        Args:
+            *senders: The senders to send messages to.
+        """
+        self._senders = senders
+
+    async def send(self, message: SenderMessageT_contra, /) -> None:
+        """Send a message.
+
+        Args:
+            message: The message to be sent.
+        """
+        for sender in self._senders:
+            await sender.send(message)

tests/experimental/test_relay_sender.py

@@ -0,0 +1,37 @@
+# License: MIT
+# Copyright © 2024 Frequenz Energy-as-a-Service GmbH
+
+"""Tests for the RelaySender class."""
+
+from frequenz.channels import Broadcast
+from frequenz.channels.experimental import RelaySender
+
+
+async def test_tee_sender() -> None:
+    """Test tee sender."""
+    channel1: Broadcast[int] = Broadcast(name="channel1")
+    channel2: Broadcast[int] = Broadcast(name="channel2")
+    channel3: Broadcast[int] = Broadcast(name="channel3")
+
+    sender = RelaySender(
+        channel1.new_sender(), channel2.new_sender(), channel3.new_sender()
+    )
+    receiver1 = channel1.new_receiver()
+    receiver2 = channel2.new_receiver()
+    receiver3 = channel3.new_receiver()
+
+    await sender.send(42)
+    assert (
+        await receiver1.receive()
+        == await receiver2.receive()
+        == await receiver3.receive()
+        == 42
+    )
+
+    await sender.send(-2)
+    assert (
+        await receiver1.receive()
+        == await receiver2.receive()
+        == await receiver3.receive()
+        == -2
+    )