"""Chat engine: message persistence, status tracking, recall."""
from datetime import datetime
from app import db
from app.models.chat import Conversation, Message, MessageStatus


class ChatEngineService:
    @staticmethod
    def get_or_create_conversation(user_id, title="新对话"):
        conv = Conversation.query.filter_by(user_id=user_id).order_by(
            Conversation.last_message_at.desc()
        ).first()
        if conv:
            return conv
        conv = Conversation(user_id=user_id, title=title)
        db.session.add(conv)
        db.session.commit()
        return conv

    @staticmethod
    def list_conversations(user_id, skip=0, limit=20):
        return Conversation.query.filter_by(user_id=user_id).order_by(
            Conversation.last_message_at.desc()
        ).offset(skip).limit(limit).all()

    @staticmethod
    def send_message(conversation_id, sender_id, content, content_type="text",
                    attachment_url=None, attachment_name=None):
        conv = Conversation.query.get(conversation_id)
        if not conv or str(conv.user_id) != str(sender_id):
            return None
        msg = Message(
            conversation_id=conversation_id,
            sender_id=sender_id,
            content=content,
            content_type=content_type or "text",
            attachment_url=attachment_url,
            attachment_name=attachment_name,
            status=MessageStatus.SENT,
        )
        db.session.add(msg)
        conv.last_message_at = datetime.utcnow()
        db.session.commit()
        return msg

    @staticmethod
    def get_messages(conversation_id, user_id, before_id=None, limit=50):
        conv = Conversation.query.get(conversation_id)
        if not conv or str(conv.user_id) != str(user_id):
            return []
        q = Message.query.filter_by(conversation_id=conversation_id).filter(
            Message.is_recalled == False
        )
        if before_id:
            before = Message.query.get(before_id)
            if before:
                q = q.filter(Message.created_at < before.created_at)
        return q.order_by(Message.created_at.desc()).limit(limit).all()

    @staticmethod
    def recall_message(message_id, user_id):
        msg = Message.query.get(message_id)
        if not msg or str(msg.sender_id) != str(user_id):
            return False
        msg.is_recalled = True
        msg.recalled_at = datetime.utcnow()
        msg.status = MessageStatus.RECALLED
        db.session.commit()
        return True

    @staticmethod
    def update_message_status(message_id, status):
        msg = Message.query.get(message_id)
        if not msg:
            return False
        msg.status = status
        db.session.commit()
        return True