"""
ByteAstra — Session management service using PyMongo.
"""
from __future__ import annotations
import json
import logging
import uuid
from datetime import datetime, timezone
from pymongo.database import Database
from app.models import Session, Message, MessageRole
from app.schemas import Citation

logger = logging.getLogger(__name__)


# ── Session operations ─────────────────────────────────────────────────────────

def create_session(db: Database, domain: str, title: str = "New Session", user_id: str | None = None) -> Session:
    doc = {
        "_id": str(uuid.uuid4()),
        "domain": domain,
        "title": title,
        "user_id": user_id,
        "subscription_tier": "free",
        "created_at": datetime.now(timezone.utc),
        "updated_at": datetime.now(timezone.utc),
    }
    db.sessions.insert_one(doc)
    logger.info("Created session %s (domain=%s) in MongoDB", doc["_id"], domain)
    return Session(doc, [])


def get_session(db: Database, session_id: str) -> Session | None:
    sess_doc = db.sessions.find_one({"_id": session_id})
    if not sess_doc:
        return None
    
    # Retrieve messages sorted by created_at ascending
    msg_docs = db.messages.find({"session_id": session_id}).sort("created_at", 1)
    messages = [Message(m) for m in msg_docs]
    return Session(sess_doc, messages)


def list_sessions(db: Database, user_id: str | None = None, limit: int = 50) -> list[Session]:
    query = {}
    if user_id:
        query["user_id"] = user_id
    
    sess_docs = db.sessions.find(query).sort("updated_at", -1).limit(limit)
    return [Session(s, []) for s in sess_docs]


def delete_session(db: Database, session_id: str) -> bool:
    res = db.sessions.delete_one({"_id": session_id})
    if res.deleted_count == 0:
        return False
    
    # Cascading delete of messages
    db.messages.delete_many({"session_id": session_id})
    return True


def update_session_title(db: Database, session_id: str, title: str) -> Session | None:
    from pymongo import ReturnDocument
    res = db.sessions.find_one_and_update(
        {"_id": session_id},
        {"$set": {"title": title, "updated_at": datetime.now(timezone.utc)}},
        return_document=ReturnDocument.AFTER
    )
    if not res:
        return None
        
    msg_docs = db.messages.find({"session_id": session_id}).sort("created_at", 1)
    messages = [Message(m) for m in msg_docs]
    return Session(res, messages)


# ── Message operations ─────────────────────────────────────────────────────────

def add_user_message(db: Database, session_id: str, content: str) -> Message:
    doc = {
        "_id": str(uuid.uuid4()),
        "session_id": session_id,
        "role": MessageRole.user.value,
        "content": content,
        "created_at": datetime.now(timezone.utc),
    }
    db.messages.insert_one(doc)
    db.sessions.update_one(
        {"_id": session_id},
        {"$set": {"updated_at": datetime.now(timezone.utc)}}
    )
    return Message(doc)


def add_assistant_message(
    db: Database,
    session_id: str,
    content: str,
    citations: list[Citation],
    is_grounded: bool,
) -> Message:
    doc = {
        "_id": str(uuid.uuid4()),
        "session_id": session_id,
        "role": MessageRole.assistant.value,
        "content": content,
        "citations_json": json.dumps([c.model_dump() for c in citations]),
        "is_grounded": is_grounded,
        "created_at": datetime.now(timezone.utc),
    }
    db.messages.insert_one(doc)
    db.sessions.update_one(
        {"_id": session_id},
        {"$set": {"updated_at": datetime.now(timezone.utc)}}
    )
    return Message(doc)


def get_recent_history(
    db: Database, session_id: str, max_turns: int = 6
) -> list[dict]:
    """
    Return recent messages as a list of OpenAI-format dicts for the prompt.
    """
    msg_docs = db.messages.find(
        {"session_id": session_id, "role": {"$ne": "system"}}
    ).sort("created_at", -1).limit(max_turns * 2)
    
    # Reverse to chronological order
    msg_list = list(reversed(list(msg_docs)))
    return [{"role": m["role"], "content": m["content"]} for m in msg_list]


def parse_citations(message: Message) -> list[Citation]:
    if not message.citations_json:
        return []
    try:
        return [Citation(**c) for c in json.loads(message.citations_json)]
    except Exception:
        return []