from datetime import datetime
import json
from . import db


class ChatSession(db.Model):
    __tablename__ = "chat_sessions"

    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey("users.id"), nullable=False)
    title = db.Column(db.String(255), default="New Chat")
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)

    messages = db.relationship(
        "ChatMessage", backref="session", lazy=True, cascade="all, delete-orphan",
        order_by="ChatMessage.created_at"
    )

    def to_dict(self):
        return {
            "id": self.id,
            "title": self.title,
            "created_at": self.created_at.isoformat(),
            "updated_at": self.updated_at.isoformat(),
        }


class ChatMessage(db.Model):
    __tablename__ = "chat_messages"

    id = db.Column(db.Integer, primary_key=True)
    session_id = db.Column(db.Integer, db.ForeignKey("chat_sessions.id"), nullable=False)
    role = db.Column(db.String(16), nullable=False)   # "user" | "assistant"
    content = db.Column(db.Text, nullable=False)
    context_ids = db.Column(db.Text, nullable=True)   # JSON list of doc/url ids used
    created_at = db.Column(db.DateTime, default=datetime.utcnow)

    def to_dict(self):
        return {
            "id": self.id,
            "role": self.role,
            "content": self.content,
            "created_at": self.created_at.isoformat(),
        }