import sqlite3
import time


LOCKED_MSGS = ("database is locked", "database is busy")


def connect(db_path, timeout=30):
    """Open a SQLite connection hardened against cross-process contention.

    Enables WAL mode and a busy timeout so that the multiple bot processes
    sharing a database file wait for each other instead of raising
    ``OperationalError: database is locked`` immediately.
    """
    conn = sqlite3.connect(db_path, timeout=timeout)
    conn.execute("PRAGMA busy_timeout=%d" % (timeout * 1000))
    conn.execute("PRAGMA journal_mode=WAL")
    return conn


def commit(conn, retries=5, backoff=0.2):
    """Commit, retrying briefly when the database is locked by another writer."""
    for attempt in range(retries):
        try:
            conn.commit()
            return
        except sqlite3.OperationalError as e:
            if str(e).lower() in LOCKED_MSGS and attempt < retries - 1:
                time.sleep(backoff * (attempt + 1))
                continue
            raise