"""MySQL connection helper (PyMySQL).

Connection settings come from environment variables so nothing is hard-coded:

    WIKI_DB_HOST      default 127.0.0.1
    WIKI_DB_PORT      default 3306
    WIKI_DB_USER      default root
    WIKI_DB_PASSWORD  default "" (empty)
    WIKI_DB_NAME      default wiki

`connect()` selects the wiki database; `connect(select_db=False)` connects to the
server without a database (used by migrate.py to CREATE DATABASE).
"""

from __future__ import annotations

import os

import pymysql
from pymysql.cursors import DictCursor


def _cfg() -> dict:
    return {
        "host": os.environ.get("WIKI_DB_HOST", "127.0.0.1"),
        "port": int(os.environ.get("WIKI_DB_PORT", "3306")),
        "user": os.environ.get("WIKI_DB_USER", "root"),
        "password": os.environ.get("WIKI_DB_PASSWORD", ""),
    }


def db_name() -> str:
    return os.environ.get("WIKI_DB_NAME", "wiki")


def connect(select_db: bool = True) -> pymysql.connections.Connection:
    kwargs = _cfg()
    if select_db:
        kwargs["database"] = db_name()
    return pymysql.connect(
        cursorclass=DictCursor,
        autocommit=True,
        charset="utf8mb4",
        **kwargs,
    )