agent-framework/python/samples/02-agents/middleware/class_based_middleware.py

# Copyright (c) Microsoft. All rights reserved.

import asyncio
import time
from collections.abc import Awaitable, Callable
from random import randint
from typing import Annotated

from agent_framework import (
    Agent,
    AgentContext,
    AgentMiddleware,
    AgentResponse,
    FunctionInvocationContext,
    FunctionMiddleware,
    Message,
    tool,
)
from agent_framework.foundry import FoundryChatClient
from azure.identity.aio import AzureCliCredential
from dotenv import load_dotenv
from pydantic import Field

# Load environment variables from .env file
load_dotenv()

"""
Class-based MiddlewareTypes Example

This sample demonstrates how to implement middleware using class-based approach by inheriting
from AgentMiddleware and FunctionMiddleware base classes. The example includes:

- SecurityAgentMiddleware: Checks for security violations in user queries and blocks requests
  containing sensitive information like passwords or secrets
- LoggingFunctionMiddleware: Logs function execution details including timing and parameters

This approach is useful when you need stateful middleware or complex logic that benefits
from object-oriented design patterns.
"""


# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production;
# see samples/02-agents/tools/function_tool_with_approval.py
# and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
@tool(approval_mode="never_require")
def get_weather(
    location: Annotated[str, Field(description="The location to get the weather for.")],
) -> str:
    """Get the weather for a given location."""
    conditions = ["sunny", "cloudy", "rainy", "stormy"]
    return f"The weather in {location} is {conditions[randint(0, 3)]} with a high of {randint(10, 30)}°C."


class SecurityAgentMiddleware(AgentMiddleware):
    """Agent middleware that checks for security violations."""

    async def process(
        self,
        context: AgentContext,
        call_next: Callable[[], Awaitable[None]],
    ) -> None:
        # Check for potential security violations in the query
        # Look at the last user message
        last_message = context.messages[-1] if context.messages else None
        if last_message and last_message.text:
            query = last_message.text
            if "password" in query.lower() or "secret" in query.lower():
                print("[SecurityAgentMiddleware] Security Warning: Detected sensitive information, blocking request.")
                # Override the result with warning message
                context.result = AgentResponse(
                    messages=[Message("assistant", ["Detected sensitive information, the request is blocked."])]
                )
                # Simply don't call call_next() to prevent execution
                return

        print("[SecurityAgentMiddleware] Security check passed.")
        await call_next()


class LoggingFunctionMiddleware(FunctionMiddleware):
    """Function middleware that logs function calls."""

    async def process(
        self,
        context: FunctionInvocationContext,
        call_next: Callable[[], Awaitable[None]],
    ) -> None:
        function_name = context.function.name
        print(f"[LoggingFunctionMiddleware] About to call function: {function_name}.")

        start_time = time.time()

        await call_next()

        end_time = time.time()
        duration = end_time - start_time

        print(f"[LoggingFunctionMiddleware] Function {function_name} completed in {duration:.5f}s.")


async def main() -> None:
    """Example demonstrating class-based middleware."""
    print("=== Class-based MiddlewareTypes Example ===")

    # For authentication, run `az login` command in terminal or replace AzureCliCredential with preferred
    # authentication option.
    async with (
        AzureCliCredential() as credential,
        Agent(
            client=FoundryChatClient(credential=credential),
            name="WeatherAgent",
            instructions="You are a helpful weather assistant.",
            tools=get_weather,
            middleware=[SecurityAgentMiddleware(), LoggingFunctionMiddleware()],
        ) as agent,
    ):
        # Test with normal query
        print("\n--- Normal Query ---")
        query = "What's the weather like in Seattle?"
        print(f"User: {query}")
        result = await agent.run(query)
        print(f"Agent: {result.text}\n")

        # Test with security-related query
        print("--- Security Test ---")
        query = "What's the password for the weather service?"
        print(f"User: {query}")
        result = await agent.run(query)
        print(f"Agent: {result.text}\n")


if __name__ == "__main__":
    asyncio.run(main())