from db_logging import log_change


def _ensure_singleton_row(cursor):
    """Ensure exactly one metadata row exists.

    The metadata table is treated as a singleton at the application level.
    Setters must ONLY update the relevant column(s) and must not wipe others.

    If the table is empty, a single default row is inserted.
    If the table contains more than one row, we raise to avoid ambiguous reads.
    """
    cursor.execute("SELECT COUNT(*) AS cnt FROM metadata")
    row = cursor.fetchone()
    cnt = int(row["cnt"]) if row and row["cnt"] is not None else 0

    if cnt == 0:
        # Rely on column defaults (e.g., defense_p default false) and nullable columns.
        cursor.execute("INSERT INTO metadata DEFAULT VALUES")
    elif cnt > 1:
        raise ValueError("metadata table must contain exactly one row")


def set_name(cursor, name):
    _ensure_singleton_row(cursor)
    cursor.execute("UPDATE metadata SET name = %s", (name,))
    log_change(cursor, f"Updated metadata name to {name}")


def get_name(cursor):
    cursor.execute("SELECT name FROM metadata LIMIT 1")
    row = cursor.fetchone()
    return row["name"] if row else None


def set_comment(cursor, comment):
    _ensure_singleton_row(cursor)
    cursor.execute("UPDATE metadata SET comment = %s", (comment,))
    log_change(cursor, f"Updated metadata comment to {comment}")


def get_comment(cursor):
    cursor.execute("SELECT comment FROM metadata LIMIT 1")
    row = cursor.fetchone()
    return row["comment"] if row else None


def set_keys(cursor, public_key, private_key):
    _ensure_singleton_row(cursor)
    cursor.execute(
        "UPDATE metadata SET public_key = %s, private_key = %s",
        (public_key, private_key),
    )
    log_change(cursor, "Updated metadata keys")


def get_public_key(cursor):
    cursor.execute("SELECT public_key FROM metadata LIMIT 1")
    row = cursor.fetchone()
    return row["public_key"] if row else None


def get_private_key(cursor):
    cursor.execute("SELECT private_key FROM metadata LIMIT 1")
    row = cursor.fetchone()
    return row["private_key"] if row else None


def set_defense_p(cursor, defense_p: bool):
    """Set the metadata defense_p flag.

    This table is treated as a singleton row at the application level.
    This setter updates ONLY defense_p and preserves all other columns.
    """
    _ensure_singleton_row(cursor)
    cursor.execute("UPDATE metadata SET defense_p = %s", (defense_p,))
    log_change(cursor, f"Updated metadata defense_p to {defense_p}")


def get_defense_p(cursor) -> bool:
    cursor.execute("SELECT defense_p FROM metadata LIMIT 1")
    row = cursor.fetchone()
    if not row or row["defense_p"] is None:
        return False
    return bool(row["defense_p"])