from sqlalchemy import create_engine, text
from sqlalchemy.orm import sessionmaker
from src.core.config import settings
from src.core.domain.db_models import Base

engine = create_engine(
    settings.SQLALCHEMY_DATABASE_URI,
    pool_recycle=300,
    pool_pre_ping=True
)

SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

def init_db():
    Base.metadata.create_all(bind=engine)
    _run_migrations()

def _run_migrations():
    """Apply any missing schema changes that create_all won't handle (existing tables)."""
    migrations = [
        "ALTER TABLE chat_history ADD COLUMN IF NOT EXISTS pinned BOOLEAN DEFAULT FALSE",
        "ALTER TABLE chat_history ADD COLUMN IF NOT EXISTS user_id INTEGER REFERENCES users(id) ON DELETE SET NULL",
    ]
    with engine.connect() as conn:
        for sql in migrations:
            try:
                conn.execute(text(sql))
            except Exception:
                pass  # Column may already exist or constraint may differ — safe to ignore
        conn.commit()

def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()