"""Database models and session management."""
from typing import Generator
from sqlalchemy import create_engine, BigInteger, String, Integer, Boolean, ForeignKey, Column
from sqlalchemy.orm import declarative_base, sessionmaker, relationship, Session
from sqlalchemy.schema import UniqueConstraint
from config import Config

Base = declarative_base()


class User(Base):
    """User model - stores user information and birthday."""
    __tablename__ = "users"
    
    user_id = Column(BigInteger, primary_key=True)
    username = Column(String, nullable=True)
    first_name = Column(String, nullable=False)
    birthday_day = Column(Integer, nullable=False)
    birthday_month = Column(Integer, nullable=False)
    birthday_year = Column(Integer, nullable=True)
    preference_theme = Column(String, nullable=False)
    
    # Relationships
    chats = relationship("UserChat", back_populates="user", cascade="all, delete-orphan")
    
    def __repr__(self):
        return f"<User(user_id={self.user_id}, first_name={self.first_name})>"


class Chat(Base):
    """Chat model - stores chat information."""
    __tablename__ = "chats"
    
    chat_id = Column(BigInteger, primary_key=True)
    chat_title = Column(String, nullable=False)
    bot_is_admin = Column(Boolean, default=False, nullable=False)
    
    # Relationships
    users = relationship("UserChat", back_populates="chat", cascade="all, delete-orphan")
    
    def __repr__(self):
        return f"<Chat(chat_id={self.chat_id}, chat_title={self.chat_title})>"


class UserChat(Base):
    """Many-to-many relationship between users and chats."""
    __tablename__ = "user_chats"
    
    user_id = Column(BigInteger, ForeignKey("users.user_id"), primary_key=True)
    chat_id = Column(BigInteger, ForeignKey("chats.chat_id"), primary_key=True)
    
    # Relationships
    user = relationship("User", back_populates="chats")
    chat = relationship("Chat", back_populates="users")
    
    __table_args__ = (
        UniqueConstraint("user_id", "chat_id", name="unique_user_chat"),
    )
    
    def __repr__(self):
        return f"<UserChat(user_id={self.user_id}, chat_id={self.chat_id})>"


# Database engine and session
engine = create_engine(Config.DATABASE_URL, echo=False)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)


def get_db() -> Generator[Session, None, None]:
    """Get database session."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def init_db() -> None:
    """Initialize database - create all tables."""
    Base.metadata.create_all(bind=engine)


def get_db_session() -> Session:
    """Get a database session (for use without context manager)."""
    return SessionLocal()