agent.py

import os
from dotenv import load_dotenv
from langgraph.graph import START, StateGraph, MessagesState
from langgraph.prebuilt import tools_condition, ToolNode
from langchain_google_genai import ChatGoogleGenerativeAI
from langchain_groq import ChatGroq
from langchain_huggingface import ChatHuggingFace, HuggingFaceEndpoint
from langchain_community.tools.tavily_search import TavilySearchResults
from langchain_community.document_loaders import WikipediaLoader, ArxivLoader
from langchain_core.messages import SystemMessage, HumanMessage
from langchain_core.tools import tool
from langchain_groq import ChatGroq

load_dotenv()



# ------------------- TOOL DEFINITIONS -------------------

@tool
def multiply(a: int, b: int) -> int:
    """Multiply two numbers."""
    return a * b

@tool
def add(a: int, b: int) -> int:
    """Add two numbers."""
    return a + b

@tool
def subtract(a: int, b: int) -> int:
    """Subtract two numbers."""
    return a - b

@tool
def divide(a: int, b: int) -> float:
    """Divide two numbers."""
    if b == 0:
        raise ValueError("Cannot divide by zero.")
    return a / b

@tool
def modulus(a: int, b: int) -> int:
    """Get the modulus of two numbers."""
    return a % b

@tool
def wiki_search(query: str) -> str:
    """Search Wikipedia for a query (max 2 results)."""
    docs = WikipediaLoader(query=query, load_max_docs=2).load()
    return "\n\n".join([doc.page_content for doc in docs])

@tool
def web_search(query: str) -> str:
    """Search the web using Tavily (max 3 results)."""
    results = TavilySearchResults(max_results=3).invoke(query)
    texts = []
    for doc in results:
        if isinstance(doc, dict):
            texts.append(doc.get("content", "") or doc.get("text", ""))
    return "\n\n".join(texts)


@tool
def arvix_search(query: str) -> str:
    """Search Arxiv for academic papers (max 3)."""
    docs = ArxivLoader(query=query, load_max_docs=3).load()
    return "\n\n".join([doc.page_content[:1000] for doc in docs])

tools = [multiply, add, subtract, divide, modulus, wiki_search, web_search, arvix_search]

# ------------------- SYSTEM PROMPT -------------------

system_prompt_path = "system_prompt.txt"
if os.path.exists(system_prompt_path):
    with open(system_prompt_path, "r", encoding="utf-8") as f:
        system_prompt = f.read()
else:
    system_prompt = (
        "You are an intelligent AI agent who can solve math, science, factual, and research-based problems. "
        "You can use tools like Wikipedia, Web search, or Arxiv when needed. Always give precise and helpful answers."
    )
sys_msg = SystemMessage(content=system_prompt)

# ------------------- GRAPH CONSTRUCTION -------------------

from langchain_openai import ChatOpenAI  # ✅ 新增导入

def build_graph(provider: str = "groq"):
    """Build the LangGraph with tool-use."""
    if provider == "google":
        llm = ChatGoogleGenerativeAI(model="gemini-2.0-flash", temperature=0)
    elif provider == "groq":
        groq_key = os.getenv("GROQ_API_KEY")
        if not groq_key:
            raise ValueError("GROQ_API_KEY is not set.")
        llm = ChatGroq(model="qwen-qwq-32b", temperature=0, api_key=groq_key)
    elif provider == "huggingface":
        llm = ChatHuggingFace(
            llm=HuggingFaceEndpoint(
                url="https://api-inference.huggingface.co/models/Meta-DeepLearning/llama-2-7b-chat-hf",
                temperature=0
            )
        )
    elif provider == "openai":
        openai_key = os.getenv("OPENAI_API_KEY")
        if not openai_key:
            raise ValueError("OPENAI_API_KEY is not set.")
        llm = ChatOpenAI(model="gpt-3.5-turbo", temperature=0, api_key=openai_key)  # ✅ OpenAI GPT
    else:
        raise ValueError("Invalid provider")

    llm_with_tools = llm.bind_tools(tools)

    def assistant(state: MessagesState):
        return {"messages": [sys_msg] + [llm_with_tools.invoke(state["messages"])]}

    # Build the graph with assistant and tools
    builder = StateGraph(MessagesState)
    builder.add_node("assistant", assistant)
    builder.add_node("tools", ToolNode(tools))

    builder.add_edge(START, "assistant")
    builder.add_conditional_edges("assistant", tools_condition)
    builder.add_edge("tools", "assistant")

    return builder.compile()

# ------------------- LOCAL TEST -------------------

if __name__ == "__main__":
    question = "When was a picture of St. Thomas Aquinas first added to the Wikipedia page on the Principle of double effect?"
    graph = build_graph(provider="openai")
    messages = graph.invoke({"messages": [HumanMessage(content=question)]})
    print("=== AI Agent Response ===")
    for m in messages["messages"]:
        m.pretty_print()