from datetime import datetime, timezone
import uuid

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

from app.db.base_class import Base

def generate_uuid() -> str:
    return uuid.uuid4().hex

def utc_now() -> datetime:
    return datetime.now(timezone.utc).replace(tzinfo=None)

class User(Base):
    __tablename__ = "users"

    id = Column(String, primary_key=True, index=True, default=generate_uuid)
    login = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)
    is_active = Column(Boolean, default=True)

    sessions = relationship("Session", back_populates="user", cascade="all, delete-orphan")
    chats = relationship("Chat", back_populates="user", cascade="all, delete-orphan")

class Session(Base):
    __tablename__ = "sessions"

    id = Column(String, primary_key=True, index=True, default=generate_uuid)
    user_id = Column(String, ForeignKey("users.id"), nullable=False, index=True)
    expires_at = Column(DateTime, nullable=False)

    user = relationship("User", back_populates="sessions")

class Chat(Base):
    __tablename__ = "chats"

    id = Column(String, primary_key=True, index=True, default=generate_uuid)
    user_id = Column(String, ForeignKey("users.id"), nullable=False, index=True)
    title = Column(String, nullable=False, default="New Chat")
    model_alias = Column(String, nullable=False)
    created_at = Column(DateTime, nullable=False, default=utc_now)
    updated_at = Column(DateTime, nullable=False, default=utc_now, onupdate=utc_now)

    user = relationship("User", back_populates="chats")
    messages = relationship("Message", back_populates="chat", cascade="all, delete-orphan", order_by="Message.created_at")

class Message(Base):
    __tablename__ = "messages"

    id = Column(String, primary_key=True, index=True, default=generate_uuid)
    chat_id = Column(String, ForeignKey("chats.id"), nullable=False, index=True)
    role = Column(String, nullable=False)  # system, user, assistant
    content = Column(Text, nullable=False)
    created_at = Column(DateTime, nullable=False, default=utc_now)

    chat = relationship("Chat", back_populates="messages")
    attachments = relationship("Attachment", back_populates="message", cascade="all, delete-orphan")

class Attachment(Base):
    __tablename__ = "attachments"

    id = Column(String, primary_key=True, index=True, default=generate_uuid)
    message_id = Column(String, ForeignKey("messages.id"), nullable=False, index=True)
    filename = Column(String, nullable=False)
    content_type = Column(String, nullable=False)
    file_path = Column(String, nullable=False)
    created_at = Column(DateTime, nullable=False, default=utc_now)

    message = relationship("Message", back_populates="attachments")