from typing import Any

from test_fixtures.mysql import MySQLConnection


def placeholders(values: list[Any]) -> str:
    """Comma-separated %s string for a SQL IN clause."""
    return ",".join(["%s"] * len(values))


def discover_single_pk(db: MySQLConnection, table_name: str) -> str:
    """Return the primary-key column name for a single-column-PK table.

    Safe to interpolate into SQL because the value comes from INFORMATION_SCHEMA,
    not from test input.
    """
    rows = db.fetchall(
        """
        SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS
        WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = %s AND COLUMN_KEY = 'PRI'
        ORDER BY ORDINAL_POSITION
        """,
        (table_name,),
    )
    pk_cols = [r["COLUMN_NAME"] for r in rows]
    assert len(pk_cols) == 1, f"Expected single-column primary key on {table_name}, got: {pk_cols}"
    return str(pk_cols[0])