from datetime import datetime

from sqlalchemy import JSON, Column, DateTime, ForeignKey, Integer, String, Text
from sqlalchemy.orm import relationship

from app.database import Base


class Conversation(Base):
    """One AI Mode thread, belonging to one learner."""

    __tablename__ = "conversations"

    id = Column(Integer, primary_key=True, index=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    title = Column(String(200), nullable=False, default="New chat")
    created_at = Column(DateTime, default=datetime.utcnow)
    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)

    messages = relationship("ConversationMessage", back_populates="conversation",
                            cascade="all, delete-orphan",
                            order_by="ConversationMessage.id")


class ConversationMessage(Base):
    """A turn in a thread.

    `citations` holds what the answer was allowed to cite *after* the server
    filtered it, so reopening a thread shows the same links it showed at the
    time — not a fresh retrieval that may now rank differently.
    """

    __tablename__ = "conversation_messages"

    id = Column(Integer, primary_key=True, index=True)
    conversation_id = Column(Integer, ForeignKey("conversations.id", ondelete="CASCADE"),
                             nullable=False, index=True)
    role = Column(String(16), nullable=False)   # user | assistant
    content = Column(Text, nullable=False)
    citations = Column(JSON, nullable=False, default=list)
    created_at = Column(DateTime, default=datetime.utcnow)

    conversation = relationship("Conversation", back_populates="messages")