"""Database engine, session helpers, bootstrap and lightweight migration."""
from __future__ import annotations

from contextlib import contextmanager
from typing import Iterator

from sqlalchemy import inspect, text
from sqlmodel import Session, SQLModel, create_engine, select

from . import config
from .auth import hash_password
from .models import Settings, User

engine = create_engine(
    config.DATABASE_URL,
    echo=False,
    connect_args={"check_same_thread": False},
)


def _migrate() -> None:
    """Add any model columns missing from existing tables (SQLite ALTER ADD).

    Keeps simple deployments upgradeable without a migration framework.
    New columns always have defaults, so a plain ADD COLUMN is sufficient.
    """
    inspector = inspect(engine)
    existing_tables = set(inspector.get_table_names())
    type_map = {"INTEGER": "INTEGER", "BOOLEAN": "BOOLEAN", "VARCHAR": "VARCHAR", "DATETIME": "DATETIME"}

    with engine.begin() as conn:
        for table in SQLModel.metadata.sorted_tables:
            if table.name not in existing_tables:
                continue
            have = {c["name"] for c in inspector.get_columns(table.name)}
            for column in table.columns:
                if column.name in have:
                    continue
                col_type = type_map.get(
                    column.type.__class__.__name__.upper(), "VARCHAR"
                )
                default = column.default.arg if column.default is not None else None
                if isinstance(default, bool):
                    default_sql = "1" if default else "0"
                elif isinstance(default, (int, float)):
                    default_sql = str(default)
                elif isinstance(default, str):
                    default_sql = f"'{default}'"
                else:
                    default_sql = "NULL"
                conn.execute(
                    text(
                        f'ALTER TABLE "{table.name}" '
                        f'ADD COLUMN "{column.name}" {col_type} DEFAULT {default_sql}'
                    )
                )


def init_db() -> None:
    """Create tables, run migration, ensure settings + admin user exist."""
    SQLModel.metadata.create_all(engine)
    _migrate()
    with Session(engine) as session:
        if session.get(Settings, 1) is None:
            session.add(
                Settings(
                    id=1,
                    default_ntfy_server=config.DEFAULT_NTFY_SERVER,
                    check_interval=config.DEFAULT_CHECK_INTERVAL,
                    auth_enabled=False,
                )
            )
            session.commit()

        # Bootstrap the first admin account if no users exist.
        if not session.exec(select(User)).first():
            session.add(
                User(
                    username=config.ADMIN_USERNAME,
                    password_hash=hash_password(config.ADMIN_PASSWORD),
                    role="admin",
                )
            )
            session.commit()


def get_settings(session: Session) -> Settings:
    settings = session.get(Settings, 1)
    if settings is None:  # safety net
        settings = Settings(id=1)
        session.add(settings)
        session.commit()
        session.refresh(settings)
    return settings


@contextmanager
def session_scope() -> Iterator[Session]:
    session = Session(engine)
    try:
        yield session
        session.commit()
    except Exception:
        session.rollback()
        raise
    finally:
        session.close()


def get_session() -> Iterator[Session]:
    """FastAPI dependency."""
    with Session(engine) as session:
        yield session


__all__ = [
    "engine",
    "init_db",
    "get_settings",
    "get_session",
    "session_scope",
    "select",
]