"""
数据库连接与初始化
"""
import re
import pymysql

try:
    from config import mysql_host as config_mysql_host
    from config import mysql_user as config_mysql_user
    from config import mysql_password as config_mysql_password
    from config import mysql_database as config_mysql_database
    from config import mysql_host_source as config_mysql_host_source
    from config import mysql_user_source as config_mysql_user_source
    from config import mysql_database_source as config_mysql_database_source
except ImportError:
    config_mysql_host = 'localhost'
    config_mysql_user = 'root'
    config_mysql_password = ''
    config_mysql_database = 'maixiang_ai'
    config_mysql_host_source = 'fallback.default'
    config_mysql_user_source = 'fallback.default'
    config_mysql_database_source = 'fallback.default'

mysql_host = config_mysql_host
mysql_user = config_mysql_user
mysql_password = config_mysql_password
mysql_database = config_mysql_database
mysql_host_source = config_mysql_host_source
mysql_user_source = config_mysql_user_source
mysql_database_source = config_mysql_database_source


def _safe_identifier(name):
    """仅允许字母、数字、下划线的数据库/表名片段，防止注入 DDL 片段。"""
    if not re.fullmatch(r'[A-Za-z0-9_]+', name or ''):
        raise ValueError(f'非法标识符: {name!r}')
    return name


def describe_db_target():
    return (
        f"{mysql_user}@{mysql_host}/{mysql_database} "
        f"(host={mysql_host_source}, user={mysql_user_source}, database={mysql_database_source})"
    )


def get_db():
    return pymysql.connect(
        host=mysql_host,
        user=mysql_user,
        password=mysql_password,
        database=mysql_database,
        charset='utf8mb4',
        cursorclass=pymysql.cursors.DictCursor
    )


def init_db():
    """确保版本公开 API 依赖的最小表结构存在。

    本进程（15124）只服务 /api/version、/api/version/latest，仅依赖 web_config 表。

    历史遗留说明（2026-09 全维度审查后删除）：这里原本还会创建 users 表、执行 role 角色
    迁移、并在查不到 super_admin 时用 ADMIN_PASSWORD（默认 admin123）插入一个超管。
    管理后台早已迁到 Java，users 表结构由 Flyway 迁移管理，本进程再写会与之冲突；
    其中「无超管即用默认密码建超管」在生产等同于后门（删除超管或改 role 枚举后本进程
    重启就会静默重建一个密码已知的超管），故整段移除。
    """
    conn = pymysql.connect(
        host=mysql_host,
        user=mysql_user,
        password=mysql_password,
        charset='utf8mb4'
    )
    try:
        db_name = _safe_identifier(mysql_database)
        with conn.cursor() as cur:
            cur.execute(f"CREATE DATABASE IF NOT EXISTS `{db_name}` DEFAULT CHARSET utf8mb4")
            cur.execute(f"USE `{db_name}`")
            cur.execute("""
                CREATE TABLE IF NOT EXISTS web_config (
                    id INT AUTO_INCREMENT PRIMARY KEY,
                    version VARCHAR(64) NOT NULL,
                    file_url VARCHAR(1024) NOT NULL,
                    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
                )
            """)
        conn.commit()
    finally:
        conn.close()