import os
from sqlalchemy import create_engine

# 延迟创建 Doris 引擎，避免在导入时卡住
LOCAL_DB_URL = "mysql+pymysql://root:DsideaL147258369@192.168.10.250:9030/yltcharge?charset=utf8mb4"
write_engine = None
local_engine = None


def _get_write_engine():
    """获取 write_engine，如果不存在则创建（延迟初始化）"""
    global write_engine, local_engine
    if write_engine is None:
        try:
            write_engine = create_engine(
                LOCAL_DB_URL,
                pool_recycle=3600,
                pool_pre_ping=True,
                connect_args={'connect_timeout': 2, 'read_timeout': 5, 'write_timeout': 5}
            )
            local_engine = write_engine
        except Exception:
            write_engine = None
            local_engine = None
    return write_engine


class Config:
    """应用配置"""
    SECRET_KEY = os.environ.get('SECRET_KEY', 'student-course-mgmt-secret-key-2024')
    
    # 数据库配置：支持 MySQL / Aliyun RDS MySQL / SQLite
    #
    # 方式1 - 自建MySQL:
    #   DB_TYPE=mysql, MYSQL_HOST, MYSQL_PORT, MYSQL_USER, MYSQL_PASSWORD, MYSQL_DB
    #
    # 方式2 - 阿里云RDS MySQL:
    #   DB_TYPE=aliyun_mysql
    #   ALIYUN_MYSQL_HOST     (必填，RDS内网/外网地址，如 rm-xxxxx.mysql.rds.aliyuncs.com)
    #   ALIYUN_MYSQL_PORT     (默认3306)
    #   ALIYUN_MYSQL_USER     (默认root)
    #   ALIYUN_MYSQL_PASSWORD (必填)
    #   ALIYUN_MYSQL_DB       (默认student_course)
    #   ALIYUN_MYSQL_SSL      (可选，设为1启用SSL连接)
    #
    # 不设置则默认使用 SQLite（开发环境）
    DB_TYPE = os.environ.get('DB_TYPE', 'sqlite').lower()
    
    if DB_TYPE == 'mysql':
        SQLALCHEMY_DATABASE_URI = os.environ.get('SQLALCHEMY_DATABASE_URI', LOCAL_DB_URL)
        SQLALCHEMY_ENGINE_OPTIONS = {
            'pool_recycle': 3600,
            'pool_pre_ping': True,
        }

    elif DB_TYPE == 'aliyun_mysql':
        ALIYUN_MYSQL_HOST = os.environ.get('ALIYUN_MYSQL_HOST', 'rm-xxxxx.mysql.rds.aliyuncs.com')
        ALIYUN_MYSQL_PORT = os.environ.get('ALIYUN_MYSQL_PORT', '3306')
        ALIYUN_MYSQL_USER = os.environ.get('ALIYUN_MYSQL_USER', 'root')
        ALIYUN_MYSQL_PASSWORD = os.environ.get('ALIYUN_MYSQL_PASSWORD', '')
        ALIYUN_MYSQL_DB = os.environ.get('ALIYUN_MYSQL_DB', 'student_course')
        ALIYUN_MYSQL_SSL = os.environ.get('ALIYUN_MYSQL_SSL', '0')

        # 构建连接URI，阿里云RDS强制utf8mb4
        _ssl_param = '&ssl=true&ssl_ca=/etc/ssl/certs/ca-certificates.crt' if ALIYUN_MYSQL_SSL == '1' else ''
        SQLALCHEMY_DATABASE_URI = (
            f'mysql+pymysql://{ALIYUN_MYSQL_USER}:{ALIYUN_MYSQL_PASSWORD}'
            f'@{ALIYUN_MYSQL_HOST}:{ALIYUN_MYSQL_PORT}/{ALIYUN_MYSQL_DB}'
            f'?charset=utf8mb4{_ssl_param}'
        )
        # 阿里云RDS推荐连接池参数：长连接 + 自动重连 + 超时回收
        SQLALCHEMY_ENGINE_OPTIONS = {
            'pool_pre_ping': True,       # 每次取连接前检测存活，避免RDS主动断连后报错
            'pool_recycle': 1800,        # RDS默认wait_timeout=28800，设1800秒回收更安全
            'pool_size': 10,             # 常驻连接数
            'max_overflow': 20,          # 峰值额外连接
            'pool_timeout': 30,          # 获取连接超时(秒)
            'connect_args': {
                'connect_timeout': 10,   # 建立TCP连接超时(秒)
                'read_timeout': 30,      # 读超时(秒)
                'write_timeout': 30,     # 写超时(秒)
            },
        }

    else:
        SQLALCHEMY_DATABASE_URI = 'sqlite:///student_course.db'
        SQLALCHEMY_ENGINE_OPTIONS = {
            'pool_pre_ping': True,
        }
    
    SQLALCHEMY_TRACK_MODIFICATIONS = False