from pymongo import MongoClient
from datetime import datetime, timezone
from core.config import MONGO_DATABASE_HOST
import uuid
import json
import re
from langchain_mongodb import MongoDBChatMessageHistory


def normalize_message(msg):
    """Normalise les messages pour LangChain/Streamlit."""
    if isinstance(msg, dict):
        if "data" in msg and "content" in msg["data"]:
            return {"type": msg.get("type", "human"), "content": msg["data"]["content"]}
        elif "type" in msg and "content" in msg:
            return {"type": msg["type"], "content": msg["content"]}
    return None


STOP_WORDS = {
    "je", "tu", "il", "elle", "on", "nous", "vous", "ils", "elles",
    "le", "la", "les", "un", "une", "des", "de", "du", "et", "en", "à",
    "pour", "comment", "quoi", "où", "qui", "que", "dans"
}

def generate_session_title(first_message: str) -> str:
    """Génère un titre cohérent à partir du premier message."""
    # Nettoyage du texte
    text = re.sub(r"[^a-zA-ZÀ-ÿ0-9\s]", "", first_message.lower())
    words = text.strip().split()
    keywords = [w for w in words if w not in STOP_WORDS]

    if not keywords:
        return "Nouvelle session"

    # Prendre les 3-5 premiers mots clés pour le titre
    title_words = keywords[:5]
    # Capitaliser les mots
    title = " ".join(w.capitalize() for w in title_words)
    

    return title


def load_all_sessions():
    """Charge toutes les sessions depuis MongoDB existantes."""
    client = MongoClient(MONGO_DATABASE_HOST)
    db = client["douane_db"]
    collection = db["chat_history"]

    all_sessions = {}
    for doc in collection.find():
        session_id = doc.get("SessionId") or str(doc.get("_id"))
        try:
            raw_messages = json.loads(doc.get("History", "[]"))
            if isinstance(raw_messages, dict):
                raw_messages = [raw_messages]
            messages = [normalize_message(m) for m in raw_messages if normalize_message(m)]
        except Exception:
            messages = []

        if not messages:
            continue

        created_at = doc.get("created_at") or doc["_id"].generation_time
        if created_at and created_at.tzinfo is None:
            created_at = created_at.replace(tzinfo=timezone.utc)

        all_sessions[session_id] = {
            "title": doc.get("title", "Session sans titre"),
            "history": messages,
            "created_at": created_at
        }

    return dict(sorted(all_sessions.items(), key=lambda x: x[1]["created_at"], reverse=True))


def start_new_session(session_state: dict) -> str:
    """Crée un nouvel ID de session en mémoire, pas encore dans MongoDB."""
    session_id = f"session_{uuid.uuid4()}"
    session_state["session_id"] = session_id
    session_state["sessions"][session_id] = {
        "history": [],
        "created_at": datetime.now(timezone.utc),
        "title": "Nouvelle session"
    }
    return session_id


def add_message_to_session(session_id: str, message: dict):
    """
    Ajoute un message dans MongoDB.
    Si c’est le premier message de la session, crée la session et génère un titre.
    """
    if "data" in message and "content" in message["data"]:
        msg = {"type": message.get("type", "human"), "content": message["data"]["content"]}
    elif "type" in message and "content" in message:
        msg = {"type": message["type"], "content": message["content"]}
    else:
        return

    client = MongoClient(MONGO_DATABASE_HOST)
    db = client["douane_db"]
    collection = db["chat_history"]

    session = collection.find_one({"SessionId": session_id})

    if session:
        try:
            history = json.loads(session.get("History", "[]"))
            if isinstance(history, dict):
                history = [history]
            elif not isinstance(history, list):
                history = []
        except:
            history = []

        history.append(msg)
        collection.update_one(
            {"SessionId": session_id},
            {"$set": {"History": json.dumps(history)}}
        )
    else:
        title = generate_session_title(msg["content"])
        collection.insert_one({
            "SessionId": session_id,
            "title": title,
            "History": json.dumps([msg]),
            "created_at": datetime.now(timezone.utc)
        })


def rename_session(session_id: str, new_title: str):
    """Renommer manuellement une session."""
    client = MongoClient(MONGO_DATABASE_HOST)
    db = client["douane_db"]
    collection = db["chat_history"]
    collection.update_one({"SessionId": session_id}, {"$set": {"title": new_title}})


def update_session_title(session_id: str):
    """
    Si la session n’a pas de titre ou a un titre générique, 
    on le met à jour avec le titre généré à partir du premier message.
    """
    client = MongoClient(MONGO_DATABASE_HOST)
    db = client["douane_db"]
    collection = db["chat_history"]

    session = collection.find_one({"SessionId": session_id})
    if not session:
        return

    title = session.get("title", "")
    if title.strip() in ["", "Nouvelle session", "Session sans titre"]:
        try:
            history = json.loads(session.get("History", "[]"))
            if isinstance(history, dict):
                history = [history]
        except:
            history = []

        if history:
            first_message = history[0].get("content", "")
            if first_message:
                new_title = generate_session_title(first_message)
                collection.update_one(
                    {"SessionId": session_id},
                    {"$set": {"title": new_title}}
                )


def get_messages_for_session(session_id: str):
    """Récupère les messages depuis MongoDB, vide si session pas encore créée."""
    client = MongoClient(MONGO_DATABASE_HOST)
    db = client["douane_db"]
    collection = db["chat_history"]

    doc = collection.find_one({"SessionId": session_id})
    if not doc:
        return []

    try:
        raw_history = json.loads(doc.get("History", "[]"))
        if isinstance(raw_history, dict):
            raw_history = [raw_history]
    except:
        raw_history = []

    messages = [normalize_message(m) for m in raw_history if normalize_message(m)]
    return messages


def get_session_history(session_id: str) -> MongoDBChatMessageHistory:
    return MongoDBChatMessageHistory(
        connection_string=MONGO_DATABASE_HOST,
        session_id=session_id,
        database_name="douane_db",
        collection_name="chat_history"
    )