import itertools
import contextlib
import logging

from typing import List, Any, Optional

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine

from website import settings


class Row(dict):
    """A dict that allows for object-like property access syntax."""

    def __getattr__(self, name):
        try:
            return self[name]
        except KeyError:
            raise AttributeError(name)


def to_json_list(cursor: Any) -> Optional[List[Row]]:
    column_names = list(cursor.keys())
    result = cursor.fetchall()
    if not result:
        return []

    return [Row(itertools.zip_longest(column_names, row)) for row in result]


def to_json(cursor):
    column_names = list(cursor.keys())
    result = cursor.fetchone()

    if not result:
        return {}

    return Row(itertools.zip_longest(column_names, result))


app_engine = create_engine(
    'mysql+pymysql://{}:{}@{}/{}?charset=utf8mb4'.format(
        settings.mysql_app['user'],
        settings.mysql_app['password'],
        settings.mysql_app['host'],
        settings.mysql_app['database']
    ),  # SQLAlchemy 数据库连接串，格式见下面
    echo=bool(settings.SQLALCHEMY_ECHO),  # 是不是要把所执行的SQL打印出来，一般用于调试
    # pool_pre_ping=True,
    # pool_size=int(settings.SQLALCHEMY_POOL_SIZE),  # 连接池大小
    # max_overflow=int(settings.SQLALCHEMY_POOL_MAX_SIZE),  # 连接池最大的大小
    # pool_recycle=int(settings.SQLALCHEMY_POOL_RECYCLE),  # 多久时间回收连接
)

Session = sessionmaker(bind=app_engine)
# Base = declarative_base(app_engine)


@contextlib.contextmanager
def get_session():
    s = Session()
    try:
        yield s
        s.commit()
    except Exception as e:
        s.rollback()
        raise e
    finally:
        s.close()