agent-framework/python/packages/main/agent_framework/_agents.py

# Copyright (c) Microsoft. All rights reserved.

from collections.abc import AsyncIterable, Callable, Sequence
from enum import Enum
from typing import Any, Protocol, TypeVar, runtime_checkable
from uuid import uuid4

from pydantic import Field

from ._clients import ChatClient
from ._pydantic import AFBaseModel
from ._types import AgentRunResponse, AgentRunResponseUpdate, ChatMessage, ChatResponse, ChatResponseUpdate, ChatRole
from .exceptions import AgentExecutionException

TThreadType = TypeVar("TThreadType", bound="AgentThread")

# region AgentThread


class AgentThread(AFBaseModel):
    """Base class for agent threads."""

    id: str | None = None

    async def on_new_messages(
        self,
        new_messages: ChatMessage | Sequence[ChatMessage],
    ) -> None:
        """Invoked when a new message has been contributed to the chat by any participant."""
        await self._on_new_messages(new_messages=new_messages)

    async def _on_new_messages(
        self,
        new_messages: ChatMessage | Sequence[ChatMessage],
    ) -> None:
        """Invoked when a new message has been contributed to the chat by any participant."""
        pass


# region MessagesRetrievableThread


@runtime_checkable
class MessagesRetrievableThread(Protocol):
    def get_messages(self) -> AsyncIterable[ChatMessage]:
        """Asynchronously retrieves all messages from thread."""
        ...


# region Agent Protocol


@runtime_checkable
class Agent(Protocol):
    """A protocol for an agent that can be invoked."""

    @property
    def id(self) -> str:
        """Returns the ID of the agent."""
        ...

    @property
    def name(self) -> str | None:
        """Returns the name of the agent."""
        ...

    @property
    def description(self) -> str | None:
        """Returns the description of the agent."""
        ...

    async def run(
        self,
        messages: str | ChatMessage | list[str | ChatMessage] | None = None,
        *,
        thread: AgentThread | None = None,
        **kwargs: Any,
    ) -> AgentRunResponse:
        """Get a response from the agent.

        This method returns the final result of the agent's execution
        as a single AgentRunResponse object. The caller is blocked until
        the final result is available.

        Note: For streaming responses, use the run_stream method, which returns
        intermediate steps and the final result as a stream of AgentRunResponseUpdate
        objects. Streaming only the final result is not feasible because the timing of
        the final result's availability is unknown, and blocking the caller until then
        is undesirable in streaming scenarios.

        Args:
            messages: The message(s) to send to the agent.
            thread: The conversation thread associated with the message(s).
            kwargs: Additional keyword arguments.

        Returns:
            An agent response item.
        """
        ...

    def run_stream(
        self,
        messages: str | ChatMessage | list[str | ChatMessage] | None = None,
        *,
        thread: AgentThread | None = None,
        **kwargs: Any,
    ) -> AsyncIterable[AgentRunResponseUpdate]:
        """Run the agent as a stream.

        This method will return the intermediate steps and final results of the
        agent's execution as a stream of AgentRunResponseUpdate objects to the caller.

        Note: An AgentRunResponseUpdate object contains a chunk of a message.

        Args:
            messages: The message(s) to send to the agent.
            thread: The conversation thread associated with the message(s).
            kwargs: Additional keyword arguments.

        Yields:
            An agent response item.
        """
        ...

    def get_new_thread(self) -> AgentThread:
        """Creates a new conversation thread for the agent."""
        ...


# region AgentBase


class AgentBase(AFBaseModel):
    """Base class for all agents.

    Attributes:
       id: The unique identifier of the agent  If no id is provided,
           a new UUID will be generated.
       name: The name of the agent
       description: The description of the agent
    """

    id: str = Field(default_factory=lambda: str(uuid4()))
    name: str = Field(default="UnnamedAgent")
    description: str | None = None

    async def _notify_thread_of_new_messages(
        self, thread: AgentThread, new_messages: ChatMessage | Sequence[ChatMessage]
    ) -> None:
        """Notify the thread of new messages."""
        if isinstance(new_messages, ChatMessage) or len(new_messages) > 0:
            await thread.on_new_messages(new_messages)


# region ChatClientAgentThread


class ChatClientAgentThreadType(Enum):
    """Defines the different supported storage locations for ChatClientAgentThread."""

    IN_MEMORY_MESSAGES = "InMemoryMessages"
    """Messages are stored in memory inside the thread object."""

    CONVERSATION_ID = "ConversationId"
    """Messages are stored in the service and the thread object just has an id reference to the service storage."""


class ChatClientAgentThread(AgentThread):
    """Chat client agent thread.

    This class manages chat threads either locally (in-memory) or via a service based on initialization.
    """

    chat_messages: list[ChatMessage] | None = None
    storage_location: ChatClientAgentThreadType | None = None

    def __init__(
        self,
        id: str | None = None,
        messages: Sequence[ChatMessage] | None = None,
        **kwargs: Any,
    ):
        """Initialize the chat client agent thread.

        Args:
            id: Service thread identifier. If provided, thread is managed by the service and messages are
            not stored locally. Must not be empty or whitespace.
            messages: Initial messages for local storage. If provided, thread is managed
            locally in-memory.
            kwargs: Additional keyword arguments.

        Raises:
            ValueError: If both id and messages are provided, or if id is empty/whitespace.

        Notes:
            - If id is set, _id is assigned and _chat_messages is None (service-managed).
            - If messages is set, _chat_messages is populated and _id is None (local).
            - If neither is provided, creates an empty local thread.
        """
        processed_messages: list[ChatMessage] | None = None
        storage_location: ChatClientAgentThreadType | None = None

        if id and messages:
            raise ValueError("Cannot specify both id and messages")

        if id:
            if not id.strip():
                raise ValueError("ID cannot be empty or whitespace")
            storage_location = ChatClientAgentThreadType.CONVERSATION_ID
        elif messages:
            processed_messages = []
            processed_messages.extend(messages)
            storage_location = ChatClientAgentThreadType.IN_MEMORY_MESSAGES

        super().__init__(
            id=id,
            chat_messages=processed_messages,  # type: ignore[reportCallIssue]
            storage_location=storage_location,  # type: ignore[reportCallIssue]
            **kwargs,
        )

    async def get_messages(self) -> AsyncIterable[ChatMessage]:
        """Get all messages in the thread."""
        for message in self.chat_messages or []:
            yield message

    async def _on_new_messages(self, new_messages: ChatMessage | Sequence[ChatMessage]) -> None:
        """Handle new messages."""
        if self.storage_location == ChatClientAgentThreadType.IN_MEMORY_MESSAGES:
            if self.chat_messages is None:
                self.chat_messages = []
            self.chat_messages.extend([new_messages] if isinstance(new_messages, ChatMessage) else new_messages)


# region ChatClientAgent


class ChatClientAgent(AgentBase):
    """A Chat Client Agent which depends on ChatClient."""

    chat_client: ChatClient

    async def run(
        self,
        messages: str | ChatMessage | list[str | ChatMessage] | None = None,
        *,
        thread: AgentThread | None = None,
        **kwargs: Any,
    ) -> AgentRunResponse:
        thread, thread_messages = await self._prepare_thread_and_messages(
            thread=thread,
            input_messages=messages,
            construct_thread=lambda: ChatClientAgentThread(),
            expected_type=ChatClientAgentThread,
        )

        response = await self.chat_client.get_response(thread_messages, **kwargs)

        self._update_thread_with_type_and_conversation_id(thread, response.conversation_id)

        # Only notify the thread of new messages if the chatResponse was successful
        # to avoid inconsistent messages state in the thread.
        await self._notify_thread_of_new_messages(thread, thread_messages)
        await self._notify_thread_of_new_messages(thread, response.messages)

        return AgentRunResponse(
            messages=response.messages,
            response_id=response.response_id,
            created_at=response.created_at,
            usage_details=response.usage_details,
            raw_representation=response.raw_representation,
            additional_properties=response.additional_properties,
        )

    async def run_stream(
        self,
        messages: str | ChatMessage | list[str | ChatMessage] | None = None,
        *,
        thread: AgentThread | None = None,
        **kwargs: Any,
    ) -> AsyncIterable[AgentRunResponseUpdate]:
        thread, thread_messages = await self._prepare_thread_and_messages(
            thread=thread,
            input_messages=messages,
            construct_thread=lambda: ChatClientAgentThread(),
            expected_type=ChatClientAgentThread,
        )

        response_updates: list[ChatResponseUpdate] = []

        streaming_response: AsyncIterable[ChatResponseUpdate] = self.chat_client.get_streaming_response(thread_messages)

        async for update in streaming_response:
            response_updates.append(update)
            yield AgentRunResponseUpdate(
                contents=update.contents,
                role=update.role,
                author_name=update.author_name,
                response_id=update.response_id,
                message_id=update.message_id,
                created_at=update.created_at,
                additional_properties=update.additional_properties,
                raw_representation=update.raw_representation,
            )

        response = ChatResponse.from_chat_response_updates(response_updates)

        self._update_thread_with_type_and_conversation_id(thread, response.conversation_id)

        # Only notify the thread of new messages if the chatResponse was successful
        # to avoid inconsistent messages state in the thread.
        await self._notify_thread_of_new_messages(thread, thread_messages)
        await self._notify_thread_of_new_messages(thread, response.messages)

    def get_new_thread(self) -> AgentThread:
        return ChatClientAgentThread()

    def _update_thread_with_type_and_conversation_id(
        self, chat_client_thread: ChatClientAgentThread, responseConversationId: str | None
    ) -> None:
        """Update thread with storage type and conversation ID.

        Args:
            chat_client_thread: The thread to update.
            responseConversationId: The conversation ID from the response, if any.

        Raises:
            AgentExecutionException: If conversation ID is missing for service-managed thread.
        """
        # Set the thread's storage location, the first time that we use it.
        if chat_client_thread.storage_location is None:
            chat_client_thread.storage_location = (
                ChatClientAgentThreadType.CONVERSATION_ID
                if responseConversationId is not None
                else ChatClientAgentThreadType.IN_MEMORY_MESSAGES
            )

        # If we got a conversation id back from the chat client, it means that the service supports server side thread
        # storage so we should capture the id and update the thread with the new id.
        if chat_client_thread.storage_location == ChatClientAgentThreadType.CONVERSATION_ID:
            if responseConversationId is None:
                raise AgentExecutionException(
                    "Service did not return a valid conversation id when using a service managed thread."
                )
            chat_client_thread.id = responseConversationId

    async def _prepare_thread_and_messages(
        self,
        *,
        thread: AgentThread | None,
        input_messages: str | ChatMessage | Sequence[str | ChatMessage] | None = None,
        construct_thread: Callable[[], TThreadType],
        expected_type: type[TThreadType],
    ) -> tuple[TThreadType, list[ChatMessage]]:
        """Prepare thread and messages for agent execution.

        Args:
            thread: The conversation thread, or None to create a new one.
            input_messages: Messages to process, can be string, ChatMessage, or sequence.
            construct_thread: Factory function to create a new thread.
            expected_type: Expected thread type for validation.

        Returns:
            Tuple of the thread and normalized messages.

        Raises:
            AgentExecutionException: If thread type is incompatible.
        """
        messages: list[ChatMessage] = []

        if thread is None:
            thread = construct_thread()

        if not isinstance(thread, expected_type):
            raise AgentExecutionException(
                f"{self.__class__.__name__} currently only supports agent threads of type {expected_type.__name__}."
            )

        # Add any existing messages from the thread to the messages to be sent to the chat client.
        if isinstance(thread, MessagesRetrievableThread):
            async for message in thread.get_messages():
                messages.append(message)

        if input_messages is None:
            input_messages = []

        if isinstance(input_messages, (str, ChatMessage)):
            input_messages = [input_messages]

        normalized_messages = [
            ChatMessage(role=ChatRole.USER, text=msg) if isinstance(msg, str) else msg for msg in input_messages
        ]

        messages.extend(normalized_messages)

        return thread, messages