# -*- coding: utf-8 -*-

# Define here the models for your spider middleware
#
# See documentation in:
# https://doc.scrapy.org/en/latest/topics/spider-middleware.html

import random

import requests
from scrapy import signals


class DoubanSpiderMiddleware(object):
    # 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 Response, 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 DoubanDownloaderMiddleware(object):
    # 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)


class RandomChangeUserAgentMiddleware(object):
    """
    随机变换UserAgent请求消息头中间件
    """

    def __init__(self, user_agent_list):
        self.user_agent_list = user_agent_list

    @classmethod
    def from_crawler(cls, crawler):
        return cls(crawler.settings.get('USER_AGENT_LIST'))

    def process_request(self, request, spider):
        user_agent = random.choice(self.user_agent_list)
        request.headers['User-Agent'] = user_agent


class RandomChangeProxyIpMiddleware(object):
    """
    随机变换代理IP中间件
    """

    def __init__(self, proxies):
        self.proxies = proxies

    @classmethod
    def from_crawler(cls, crawler):
        # 程序启动时，动态获取一批代理IP，供后续随机切换使用
        proxies = ['181.30.3.234:3128', '58.11.67.120:3128', '201.166.23.226:8080', '109.197.188.8:8080',
                   '88.99.149.188:31288', '93.87.28.42:53281', '49.48.130.147:8080', '212.8.252.110:1080',
                   '101.96.10.4:80', '101.96.10.63:8080']
        return cls(proxies)

    def process_request(self, request, spider):
        # 代理IP来源于西刺代理，不过质量并不高，很多不能用
        # http://www.xicidaili.com/nn/
        # request.meta['proxy'] = 'http://118.190.95.43:9001'
        # 后改为从 https://github.com/jhao104/proxy_pool 提供的测试地址获取
        # http://123.207.35.36:5010/get/
        request.meta['proxy'] = random.choice(self.proxies)
