from sqlalchemy import create_engine, event
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from config import get_settings

settings = get_settings()

engine = create_engine(
    settings.DATABASE_URL,
    connect_args={"check_same_thread": False},
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()


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


def create_tables():
    Base.metadata.create_all(bind=engine)


def run_migrations():
    """Apply lightweight schema migrations for SQLite."""
    from sqlalchemy import inspect, text
    insp = inspect(engine)

    # AuditLog: add username column if missing
    if "audit_log" in insp.get_table_names():
        audit_cols = {c["name"] for c in insp.get_columns("audit_log")}
        if "username" not in audit_cols:
            with engine.connect() as conn:
                conn.execute(text("ALTER TABLE audit_log ADD COLUMN username TEXT"))
                conn.commit()

    # Heartbeat: add missing columns
    if "heartbeats" in insp.get_table_names():
        hb_cols = {c["name"] for c in insp.get_columns("heartbeats")}
        new_hb_cols = [
            ("sessions", "TEXT"),
            ("ram_used_gb", "REAL"),
            ("ram_available_gb", "REAL"),
            ("swap_total_gb", "REAL"),
            ("swap_used_gb", "REAL"),
            ("swap_free_gb", "REAL"),
            ("swap_percent", "REAL"),
        ]
        with engine.connect() as conn:
            for col, col_type in new_hb_cols:
                if col not in hb_cols:
                    conn.execute(text(f"ALTER TABLE heartbeats ADD COLUMN {col} {col_type}"))
            conn.commit()

    # Computer: add missing columns
    if "computers" in insp.get_table_names():
        pc_cols = {c["name"] for c in insp.get_columns("computers")}
        new_pc_cols = [
            ("current_ram_used_gb", "REAL"),
            ("current_ram_available_gb", "REAL"),
            ("current_swap_total_gb", "REAL"),
            ("current_swap_used_gb", "REAL"),
            ("current_swap_free_gb", "REAL"),
            ("current_swap_percent", "REAL"),
        ]
        with engine.connect() as conn:
            for col, col_type in new_pc_cols:
                if col not in pc_cols:
                    conn.execute(text(f"ALTER TABLE computers ADD COLUMN {col} {col_type}"))
            conn.commit()