from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from flask_login import LoginManager
from sqlalchemy import event
from sqlalchemy.engine import Engine
import sqlite3

db = SQLAlchemy()
migrate = Migrate()
login_manager = LoginManager()
login_manager.login_view = 'auth.login'
login_manager.login_message = 'Please log in to access this page.'
login_manager.login_message_category = 'warning'


@event.listens_for(Engine, "connect")
def _set_sqlite_pragma(dbapi_connection, connection_record):
    """Enable WAL mode and sane concurrency settings for SQLite.

    WAL lets readers and writers operate concurrently, which prevents
    'database is locked' errors when running under multi-worker Gunicorn.
    """
    if isinstance(dbapi_connection, sqlite3.Connection):
        cursor = dbapi_connection.cursor()
        cursor.execute("PRAGMA journal_mode=WAL")
        cursor.execute("PRAGMA busy_timeout=5000")
        cursor.execute("PRAGMA synchronous=NORMAL")
        cursor.close()