import json
from datetime import date, datetime

import psycopg2
from psycopg2 import pool
from psycopg2.extras import RealDictCursor
from Config import *

# 创建连接池
postgresql_pool = psycopg2.pool.SimpleConnectionPool(
    minconn=1,
    maxconn=10,
    host=PG_HOST,
    port=PG_PORT,
    dbname=PG_DATABASE,
    user=PG_USER,
    password=PG_PASSWORD
)


class PostgreSQLUtil:
    def __init__(self, connection):
        self.connection = connection

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.connection.commit()
        postgresql_pool.putconn(self.connection)

    def execute_query(self, sql, params=None, return_dict=True):
        """执行查询并返回结果"""
        try:
            with self.connection.cursor(
                    cursor_factory=RealDictCursor if return_dict else None
            ) as cursor:
                cursor.execute(sql, params)

                if cursor.description:
                    columns = [desc[0] for desc in cursor.description]
                    results = cursor.fetchall()

                    # 转换字典格式
                    if return_dict:
                        return results
                    else:
                        return [dict(zip(columns, row)) for row in results]
                else:
                    return {"rowcount": cursor.rowcount}

        except Exception as e:
            print(f"执行SQL出错: {e}")
            self.connection.rollback()
            raise


def get_db():
    connection = postgresql_pool.getconn()
    try:
        yield PostgreSQLUtil(connection)
    finally:
        postgresql_pool.putconn(connection)


# 使用示例
if __name__ == "__main__":
    '''
    db_gen = get_db()：调用生成器函数，返回生成器对象。
    db = next(db_gen)：从生成器中获取 PostgreSQLUtil 实例。
    生成器函数确保连接在使用后正确归还到连接池。
    '''
    # 从生成器中获取数据库实例
    db_gen = get_db()
    db = next(db_gen)
    try:
        # 示例查询
        result = db.execute_query("SELECT version()")
        print("数据库版本:", result)

        # 返回JSON
        json_data = db.query_to_json("SELECT * FROM t_base_class LIMIT 2")
        print("JSON结果:", json_data)
    finally:
        # 手动关闭生成器
        db_gen.close()