# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://docs.scrapy.org/en/latest/topics/item-pipeline.html


# useful for handling different item types with a single interface
import mysql.connector
from scrapy.exceptions import DropItem
from .items import NewsItem
from .settings import MYSQL_USERNAME, MYSQL_PASSWORD, MYSQL_HOST, MYSQL_PORT, MYSQL_DATABASE


class DecspiderPipeline:
    def open_spider(self, spider):
        # 连接数据库
        self.conn = mysql.connector.connect(user=MYSQL_USERNAME, password=MYSQL_PASSWORD, host=MYSQL_HOST, database=MYSQL_DATABASE, port=MYSQL_PORT)
        self.cursor = self.conn.cursor()

        # 动态生成表名
        self.table_name = f'{spider.settings.get("BOT_NAME")}_{spider.name}'
        spider.log(f'Dataset name: {self.table_name}')

        # 检查表是否存在，如果不存在就创建表
        self.cursor.execute(f"""
            CREATE TABLE IF NOT EXISTS `{self.table_name}` (
                id INT AUTO_INCREMENT PRIMARY KEY
            )
        """)

        # 获取当前表的列信息
        self.cursor.execute(f"SHOW COLUMNS FROM `{self.table_name}`")
        existing_columns = {row[0] for row in self.cursor.fetchall()}

        # 获取 NewsItem 字段信息
        item_columns = set(NewsItem.fields.keys())

         # 添加 NewsItem 字段到表中
        for column in item_columns:
            if column not in existing_columns:
                self.cursor.execute(f"ALTER TABLE `{self.table_name}` ADD COLUMN `{column}` TEXT")
                spider.log(f'Added column `{column}` to `{self.table_name}` table')

        # 删除表中不存在于 NewsItem 中的字段
        for column in existing_columns:
            if column not in item_columns and column != 'id':
                self.cursor.execute(f"ALTER TABLE `{self.table_name}` DROP COLUMN `{column}`")
                spider.log(f'Dropped column `{column}` from `{self.table_name}` table')

        self.conn.commit()


    def close_spider(self, spider):
        self.conn.close()


    def process_item(self, item, spider):

        if isinstance(item, NewsItem):    
            # 插入数据
            columns = ', '.join(item.keys())
            placeholders = ', '.join(['%s'] * len(item))
            sql = f"INSERT INTO `{self.table_name}` ({columns}) VALUES ({placeholders})"

            try:
                self.cursor.execute(sql, list(item.values()))
                self.conn.commit()
            except mysql.connector.Error as e:
                spider.log(f"Error when inserting item: {e}")
                self.conn.rollback()
                raise DropItem(f"Error when inserting item: {e}")

        return item