import getpass
import os
import time
from typing import Annotated, Optional
from typing import TypedDict

from dotenv import load_dotenv
from langchain_core.tools.retriever import create_retriever_tool
from langchain_chroma import Chroma
from langchain_core.messages import AnyMessage, HumanMessage, SystemMessage
from langchain_google_genai import ChatGoogleGenerativeAI
from langchain_huggingface import ChatHuggingFace, HuggingFaceEmbeddings, HuggingFaceEndpoint
from langchain_openai import ChatOpenAI
from langgraph.graph import START, StateGraph
from langgraph.graph.message import add_messages
from langgraph.prebuilt import ToolNode, tools_condition

from tools import get_tools

load_dotenv()

MAX_AGENT_INVOKE_RETRIES = 3
INITIAL_AGENT_RETRY_BACKOFF = 1.0
INFERENCE_MODE = "hugging-face"  # Change to "hugging-face" or "open-ai" to use those providers instead


class AgentState(TypedDict):
    messages: Annotated[list[AnyMessage], add_messages]


class BasicAgent:
    def __init__(self):
        self.sys_msg = self.get_system_prompt()
        self.llm = self.get_llm()
        self.tools = self._load_tools()
        self.chat_with_tools = self.llm.bind_tools(self.tools)
        self._graph = self._build_graph()
        print("BasicAgent initialized.")

    def _load_tools(self):
        """Return tool list, appending a ChromaDB retriever tool if available."""
        tools = get_tools()
        try:
            embeddings = HuggingFaceEmbeddings(
                model_name="sentence-transformers/all-mpnet-base-v2"
            )
            vector_store = Chroma(
                collection_name="gaia_questions",
                embedding_function=embeddings,
                persist_directory="./chroma_db",
            )
            retriever_tool = create_retriever_tool(
                retriever=vector_store.as_retriever(),
                name="question_search",
                description=(
                    "Search for similar past questions. Returns solved examples with the answer "
                    "and which tools/strategies were used — useful for picking the right approach."
                ),
            )
            tools.append(retriever_tool)
        except Exception as e:
            print(f"Warning: could not initialise ChromaDB retriever: {e}")
        return tools

    def get_system_prompt(self):
        prompt_path = os.path.join(os.path.dirname(__file__), "system_prompt.md")
        with open(prompt_path, "r", encoding="utf-8") as f:
            system_prompt = f.read()
        return SystemMessage(content=system_prompt)

    def get_llm(self):
        global INFERENCE_MODE
        supported_modes = ["google", "hugging-face", "open-ai"]
        match INFERENCE_MODE.lower():
            case "google":
                model = "gemini-2.0-flash"
                if "GOOGLE_API_KEY" not in os.environ:
                    os.environ["GOOGLE_API_KEY"] = getpass.getpass(
                        "Please enter your Google AI API key: "
                    )
                return ChatGoogleGenerativeAI(model=model, temperature=0)
            case "hugging-face":
                repo_id = "Qwen/Qwen3-Coder-30B-A3B-Instruct"
                return ChatHuggingFace(
                    llm=HuggingFaceEndpoint(
                        repo_id=repo_id,
                        task="text-generation",
                        temperature=0.01,  # HF serverless doesn't support temperature=0
                    ),
                    verbose=True,
                )
            case "open-ai":
                model = "gpt-4o-mini"
                if "OPENAI_API_KEY" not in os.environ:
                    os.environ["OPENAI_API_KEY"] = getpass.getpass(
                        "Please enter your OPEN AI API key: "
                    )
                return ChatOpenAI(model=model, temperature=0)
            case _:
                raise ValueError(
                    f"Invalid inference mode: {INFERENCE_MODE}. "
                    f"Please choose from supported modes: {', '.join(supported_modes)}"
                )

    def assistant(self, state: AgentState):
        return {
            "messages": [self.chat_with_tools.invoke([self.sys_msg] + state["messages"])]
        }

    def _build_graph(self):
        builder = StateGraph(AgentState)
        builder.add_node("assistant", self.assistant)
        builder.add_node("tools", ToolNode(self.tools))

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

    @property
    def graph(self):
        return self._graph

    def __call__(
        self,
        question: str,
        file_url: Optional[str] = None,
        file_name: Optional[str] = None,
    ) -> str:
        if file_url:
            file_ext = os.path.splitext(file_name)[1].lower()
            local_file_path = f"./files/{file_name}"
            prompt = (
                f"{question}\n\n"
                f"Attached file url:\n{file_url}\n\n"
                f"Attached file extension:\n{file_ext}\n\n"
                f"If file doesn't exist at {file_url}, you can access the file locally at {local_file_path}."
            )
        else:
            prompt = question

        messages = [HumanMessage(content=prompt)]
        response = self.invoke_agent_with_retries(messages)

        for m in response["messages"]:
            if len(m.content) < 1000:
                m.pretty_print()
            else:
                m.content = m.content[:500] + "..." + m.content[-500:]
                m.pretty_print()

        answer = response["messages"][-1].content
        if "FINAL ANSWER: " in answer:
            return answer.split("FINAL ANSWER: ")[1]
        return answer

    def invoke_agent_with_retries(self, messages: list[AnyMessage]):
        backoff = INITIAL_AGENT_RETRY_BACKOFF
        for attempt in range(1, MAX_AGENT_INVOKE_RETRIES + 1):
            try:
                return self.graph.invoke({"messages": messages})
            except Exception as exc:
                if attempt == MAX_AGENT_INVOKE_RETRIES:
                    print(f"Agent invocation failed after {attempt} attempts: {exc}")
                    raise
                print(
                    f"Agent invocation attempt {attempt} failed ({exc}); "
                    f"retrying in {backoff:.1f}s..."
                )
                time.sleep(backoff)
                backoff *= 2


# Stable runtime graph for LangSmith traceability
__all__ = ["BasicAgent", "get_agent", "get_graph"]

_AGENT_SINGLETON: Optional[BasicAgent] = None


def get_agent() -> BasicAgent:
    global _AGENT_SINGLETON
    if _AGENT_SINGLETON is None:
        _AGENT_SINGLETON = BasicAgent()
    return _AGENT_SINGLETON


def get_graph():
    return get_agent().graph