chore: import upstream snapshot with attribution

python/semantic_kernel/agents/strategies/selection/sequential_selection_strategy.py

@@ -0,0 +1,80 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+import logging
+import sys
+
+if sys.version_info >= (3, 12):
+    from typing import override  # pragma: no cover
+else:
+    from typing_extensions import override  # pragma: no cover
+
+from typing import TYPE_CHECKING
+
+from pydantic import PrivateAttr
+
+from semantic_kernel.agents.strategies.selection.selection_strategy import SelectionStrategy
+from semantic_kernel.utils.feature_stage_decorator import experimental
+
+if TYPE_CHECKING:
+    from semantic_kernel.agents import Agent
+    from semantic_kernel.contents.chat_message_content import ChatMessageContent
+
+
+logger: logging.Logger = logging.getLogger(__name__)
+
+
+@experimental
+class SequentialSelectionStrategy(SelectionStrategy):
+    """Round-robin turn-taking strategy. Agent order is based on the order in which they joined."""
+
+    _index: int = PrivateAttr(default=-1)
+
+    def reset(self) -> None:
+        """Reset selection to the initial/first agent."""
+        self._index = -1
+
+    def _increment_index(self, agent_count: int) -> None:
+        """Increment the index in a circular manner."""
+        self._index = (self._index + 1) % agent_count
+
+    @override
+    async def select_agent(
+        self,
+        agents: list["Agent"],
+        history: list["ChatMessageContent"],
+    ) -> "Agent":
+        """Select the next agent in a round-robin fashion.
+
+        Args:
+            agents: The list of agents to select from.
+            history: The history of messages in the conversation.
+
+        Returns:
+            The agent who takes the next turn.
+        """
+        if self._index >= len(agents):
+            self._index = -1
+
+        if (
+            self.has_selected
+            and self.initial_agent is not None
+            and len(agents) > 0
+            and agents[0] == self.initial_agent
+            and self._index < 0
+        ):
+            # Avoid selecting the same agent twice in a row
+            self._increment_index(len(agents))
+
+        # Main index increment
+        self._increment_index(len(agents))
+
+        # Pick the agent
+        agent = agents[self._index]
+
+        logger.info(
+            "Selected agent at index %d (ID: %s, name: %s)",
+            self._index,
+            agent.id,
+            agent.name,
+        )
+        return agent