app/agent_fallback.py

"""
LangGraph-based agent fallback for complex quiz solving.
Used when structured strategies fail or for novel quiz types.
"""
import os
import logging
import time
from typing import Dict, Any, Optional, List, Annotated
from typing_extensions import TypedDict

logger = logging.getLogger(__name__)

# Try to import LangGraph components (optional dependency)
try:
    from langgraph.graph import StateGraph, END, START
    from langgraph.prebuilt import ToolNode
    from langchain_core.messages import trim_messages, HumanMessage
    from langchain.chat_models import init_chat_model
    from langgraph.graph.message import add_messages
    from langchain_core.rate_limiters import InMemoryRateLimiter
    LANGGRAPH_AVAILABLE = True
except ImportError:
    LANGGRAPH_AVAILABLE = False
    logger.warning("LangGraph not available - agent fallback disabled")


class AgentState(TypedDict):
    """State for LangGraph agent."""
    messages: Annotated[List, add_messages]


class AgentFallback:
    """Agent-based fallback solver using LangGraph."""
    
    def __init__(self, email: str, secret: str):
        self.email = email
        self.secret = secret
        self.agent = None
        self.tools = []
        
        if LANGGRAPH_AVAILABLE:
            self._initialize_agent()
    
    def _initialize_agent(self):
        """Initialize the LangGraph agent."""
        try:
            # Define tools (simplified - you'd import from your tools module)
            # For now, we'll create a minimal agent
            
            # Initialize LLM with rate limiting
            rate_limiter = InMemoryRateLimiter(
                requests_per_second=4 / 60,
                check_every_n_seconds=1,
                max_bucket_size=4
            )
            
            llm = init_chat_model(
                model_provider="google_genai",
                model="gemini-2.5-flash",
                rate_limiter=rate_limiter
            )
            
            # Create simple graph (you'd add your tools here)
            graph = StateGraph(AgentState)
            graph.add_node("agent", self._agent_node)
            graph.add_edge(START, "agent")
            graph.add_conditional_edges("agent", self._route, {END: END})
            
            self.agent = graph.compile()
            logger.info("Agent fallback initialized")
            
        except Exception as e:
            logger.error(f"Error initializing agent: {e}")
            self.agent = None
    
    def _agent_node(self, state: AgentState):
        """Agent node that processes messages."""
        # Simplified - would use actual LLM here
        return {"messages": state["messages"]}
    
    def _route(self, state: AgentState):
        """Route logic for agent."""
        return END
    
    async def solve(self, question: str, page_content: Dict[str, Any], 
                   remaining_time: float) -> Optional[Any]:
        """
        Attempt to solve using agent-based approach.
        
        Args:
            question: Question text
            page_content: Page content
            remaining_time: Time remaining in seconds
            
        Returns:
            Answer if solved, None otherwise
        """
        if not LANGGRAPH_AVAILABLE or not self.agent:
            return None
        
        # Only use agent if we have enough time
        if remaining_time < 30.0:
            logger.debug("Skipping agent fallback - insufficient time")
            return None
        
        try:
            logger.info("Attempting agent-based solution...")
            
            system_prompt = f"""
            You are a quiz-solving agent. Solve this question:
            
            Question: {question}
            
            Page Content: {page_content.get('text', '')[:2000]}
            
            Email: {self.email}
            Secret: {self.secret}
            
            Provide a clear, concise answer.
            """
            
            initial_messages = [
                {"role": "system", "content": system_prompt},
                {"role": "user", "content": question}
            ]
            
            # Run agent with timeout
            result = self.agent.invoke(
                {"messages": initial_messages},
                config={"recursion_limit": 100}
            )
            
            # Extract answer from result
            if result and "messages" in result:
                last_message = result["messages"][-1]
                if hasattr(last_message, "content"):
                    return last_message.content
                elif isinstance(last_message, dict) and "content" in last_message:
                    return last_message["content"]
            
            return None
            
        except Exception as e:
            logger.error(f"Error in agent fallback: {e}")
            return None


def get_agent_fallback(email: str, secret: str) -> Optional[AgentFallback]:
    """Get or create agent fallback instance."""
    if not LANGGRAPH_AVAILABLE:
        return None
    return AgentFallback(email, secret)