import sqlite3
import threading
from pathlib import Path


class DatabasePool:
    def __init__(self, db: Path) -> None:
        self.db: Path = db
        self._local: threading.local = threading.local()
        self._conns: list[sqlite3.Connection] = []

    def get_conn(self) -> sqlite3.Connection:
        if getattr(self._local, 'conn', None) is None:
            self._local.conn = get_conn(self.db)
            self._conns.append(self._local.conn)
        return self._local.conn

    def close(self):
        for c in self._conns:
            c.close()

def get_conn(db: Path) -> sqlite3.Connection:
    conn = sqlite3.connect(db, autocommit=True, check_same_thread=False)
    conn.row_factory = sqlite3.Row
    _ = conn.executescript("""
        PRAGMA journal_mode = WAL;
        PRAGMA mmap_size = 134217728;
        PRAGMA cache_size = 4000;
        PRAGMA synchronous = NORMAL;
        PRAGMA foreign_keys = ON;
    """)
    return conn