text: # -*- coding: utf-8 -*-
  
  # Define here the models for your spider middleware
  #
  # See documentation in:
  # https://docs.scrapy.org/en/latest/topics/spider-middleware.html
  
  import os
  import random
  
  from scrapy import signals
  from scrapy.exceptions import NotConfigured
  
  
  class OsScrapyRandomUseragentSpiderMiddleware:
      # Not all methods need to be defined. If a method is not defined,
      # scrapy acts as if the spider middleware does not modify the
      # passed objects.
  
      @classmethod
      def from_crawler(cls, crawler):
          # This method is used by Scrapy to create your spiders.
          s = cls()
          crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
          return s
  
      def process_spider_input(self, response, spider):
          # Called for each response that goes through the spider
          # middleware and into the spider.
  
          # Should return None or raise an exception.
          return None
  
      def process_spider_output(self, response, result, spider):
          # Called with the results returned from the Spider, after
          # it has processed the response.
  
          # Must return an iterable of Request, dict or Item objects.
          for i in result:
              yield i
  
      def process_spider_exception(self, response, exception, spider):
          # Called when a spider or process_spider_input() method
          # (from other spider middleware) raises an exception.
  
          # Should return either None or an iterable of Request, dict
          # or Item objects.
          pass
  
      def process_start_requests(self, start_requests, spider):
          # Called with the start requests of the spider, and works
          # similarly to the process_spider_output() method, except
          # that it doesn’t have a response associated.
  
          # Must return only requests (not items).
          for r in start_requests:
              yield r
  
      def spider_opened(self, spider):
          spider.logger.info("Spider opened: %s" % spider.name)
  
  
  class OsScrapyRandomUseragentDownloaderMiddleware:
      # Not all methods need to be defined. If a method is not defined,
      # scrapy acts as if the downloader middleware does not modify the
      # passed objects.
  
      @classmethod
      def from_crawler(cls, crawler):
          # This method is used by Scrapy to create your spiders.
          s = cls()
          crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
          return s
  
      def process_request(self, request, spider):
          # Called for each request that goes through the downloader
          # middleware.
  
          # Must either:
          # - return None: continue processing this request
          # - or return a Response object
          # - or return a Request object
          # - or raise IgnoreRequest: process_exception() methods of
          #   installed downloader middleware will be called
          return None
  
      def process_response(self, request, response, spider):
          # Called with the response returned from the downloader.
  
          # Must either;
          # - return a Response object
          # - return a Request object
          # - or raise IgnoreRequest
          return response
  
      def process_exception(self, request, exception, spider):
          # Called when a download handler or a process_request()
          # (from other downloader middleware) raises an exception.
  
          # Must either:
          # - return None: continue processing this exception
          # - return a Response object: stops process_exception() chain
          # - return a Request object: stops process_exception() chain
          pass
  
      def spider_opened(self, spider):
          spider.logger.info("Spider opened: %s" % spider.name)
  
  
  def bytes_to_text(s):
      if isinstance(s, bytes):
          return s.decode("utf-8")
      return s
  
  
  class RandomUserAgentMiddleware(object):
      def __init__(self, crawler):
          self.crawler = crawler
          self.ua_list = []
          self.default_useragent = bytes_to_text(crawler.settings.get("USER_AGENT"))
          try:
              self.load()
          except Exception as e:
              raise NotConfigured(f"load fail {e}")
  
      def process_request(self, request, spider):
          request_useragent = request.headers.get("User-Agent", None)
          if (
              not request_useragent
              or bytes_to_text(request_useragent) == self.default_useragent
          ):
              ua = random.choice(self.ua_list)
              request.headers.setlist(b"User-Agent", ua)
  
      def load(self):
          u = self.crawler.settings.get("USER_AGENTS")
          if isinstance(u, list):
              uas = [x.strip() for x in u if len(x.strip()) > 0]
              if len(uas) <= 0:
                  raise Exception("no available useragent")
              self.ua_list = uas
              return
          elif isinstance(u, str):
              u = u.strip()
              if os.path.isfile(u):
                  with open(u, "r") as f:
                      uas = [x.strip() for x in f.readlines() if len(x.strip()) > 0]
                      if len(uas) <= 0:
                          raise Exception(f"no useragent in file {u}")
                      self.ua_list = uas
              else:
                  if len(u) <= 0:
                      raise Exception(f"empty string")
                  self.ua_list = [u]
              return
          raise Exception(f"invalid USER_AGENTS {u}")
  
      @classmethod
      def from_crawler(cls, crawler):
          if crawler.settings.get("USER_AGENTS", None) is None:
              raise NotConfigured("not set USER_AGENTS")
          return cls(crawler)
  