"""Shared SQLite primitives for the small per-profile / board stores."""

from __future__ import annotations

import contextlib
import sqlite3


def add_column_if_missing(conn: sqlite3.Connection, table: str, column: str, ddl: str) -> bool:
    """``ALTER TABLE <table> ADD COLUMN <ddl>``, idempotent across races.

    Returns True when this call added the column; swallows the ``duplicate column name`` error a
    concurrent migrator may have caused. ``column`` is the human-readable name, ``ddl`` the
    actual definition.
    """
    try:
        conn.execute(f"ALTER TABLE {table} ADD COLUMN {ddl}")
        return True
    except sqlite3.OperationalError as exc:
        if "duplicate column name" in str(exc).lower():
            return False
        raise


@contextlib.contextmanager
def write_txn(conn: sqlite3.Connection):
    """An IMMEDIATE write transaction: at most one concurrent writer wins.

    The explicit ROLLBACK is guarded so a SQLite auto-rollback (no active transaction left under EIO
    / lock contention / corruption) cannot shadow the original exception with a spurious rollback
    error.
    """
    conn.execute("BEGIN IMMEDIATE")
    try:
        yield conn
    except Exception:
        try:
            conn.execute("ROLLBACK")
        except sqlite3.OperationalError:
            pass
        raise
    else:
        conn.execute("COMMIT")