from sqlalchemy import create_engine, inspect, text
from sqlalchemy.orm import sessionmaker, DeclarativeBase
import os

DB_PATH = os.environ.get("DB_PATH", "/app/data/agents.db")
engine = create_engine(f"sqlite:///{DB_PATH}", connect_args={"check_same_thread": False})
SessionLocal = sessionmaker(bind=engine)


class Base(DeclarativeBase):
    pass


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


def _ensure_column(conn, table: str, column: str, ddl: str):
    """Add a column to an existing table if it doesn't exist (SQLite idempotent migration)."""
    insp = inspect(conn)
    cols = {c["name"] for c in insp.get_columns(table)}
    if column not in cols:
        conn.execute(text(f"ALTER TABLE {table} ADD COLUMN {column} {ddl}"))
        print(f"  migration: added {table}.{column}")


def init_db():
    Base.metadata.create_all(bind=engine)
    with engine.begin() as conn:
        # Additive columns on existing tables (safe to re-run)
        _ensure_column(conn, "runs", "result", "JSON")
        _ensure_column(conn, "runs", "triggered_by", "VARCHAR DEFAULT ''")
        _ensure_column(conn, "agent_catalog", "result_schema", "JSON")