from enum import Enum, unique
from queue import Queue
from random import random
from threading import Thread, current_thread
from time import sleep
from urllib.parse import urlparse

import requests
from bs4 import BeautifulSoup


@unique
class SpiderStatus(Enum):
    IDLE = 0
    WORKING = 1


def decode_page(page_bytes, charsets=('utf-8',)):
    page_html = None
    for charset in charsets:
        try:
            page_html = page_bytes.decode(charset)
            break
        except UnicodeDecodeError:
            pass
    return page_html


class Retry(object):

    def __init__(self, *, retry_times=3,
                 wait_secs=5, errors=(Exception, )):
        self.retry_times = retry_times
        self.wait_secs = wait_secs
        self.errors = errors

    def __call__(self, fn):

        def wrapper(*args, **kwargs):
            for _ in range(self.retry_times):
                try:
                    return fn(*args, **kwargs)
                except self.errors as e:
                    print(e)
                    sleep((random() + 1) * self.wait_secs)
            return None

        return wrapper


class Spider(object):

    def __init__(self):
        self.status = SpiderStatus.IDLE

    @Retry()
    def fetch(self, current_url, *, charsets=('utf-8', ),
              user_agent=None, proxies=None):
        thread_name = current_thread().name
        print(f'[{thread_name}]: {current_url}')
        headers = {'user-agent': user_agent} if user_agent else {}
        resp = requests.get(current_url,
                            headers=headers, proxies=proxies)
        return decode_page(resp.content, charsets) \
            if resp.status_code == 200 else None

    def parse(self, html_page, *, domain='m.sohu.com'):
        soup = BeautifulSoup(html_page, 'lxml')
        url_links = []
        for a_tag in soup.body.select('a[href]'):
            parser = urlparse(a_tag.attrs['href'])
            scheme = parser.scheme or 'http'
            netloc = parser.netloc or domain
            if scheme != 'javascript' and netloc == domain:
                path = parser.path
                query = '?' + parser.query if parser.query else ''
                full_url = f'{scheme}://{netloc}{path}{query}'
                if full_url not in visited_urls:
                    url_links.append(full_url)
        return url_links

    def extract(self, html_page):
        pass

    def store(self, data_dict):
        pass


class SpiderThread(Thread):

    def __init__(self, name, spider, tasks_queue):
        super().__init__(name=name, daemon=True)
        self.spider = spider
        self.tasks_queue = tasks_queue

    def run(self):
        while True:
            current_url = self.tasks_queue.get()
            visited_urls.add(current_url)
            self.spider.status = SpiderStatus.WORKING
            html_page = self.spider.fetch(current_url)
            if html_page not in [None, '']:
                url_links = self.spider.parse(html_page)
                for url_link in url_links:
                    self.tasks_queue.put(url_link)
            self.spider.status = SpiderStatus.IDLE


def is_any_alive(spider_threads):
    return any([spider_thread.spider.status == SpiderStatus.WORKING
                for spider_thread in spider_threads])


visited_urls = set()


def main():
    task_queue = Queue()
    task_queue.put('http://m.sohu.com/')
    spider_threads = [SpiderThread('thread-%d' % i, Spider(), task_queue)
                      for i in range(10)]
    for spider_thread in spider_threads:
        spider_thread.start()

    while not task_queue.empty() or is_any_alive(spider_threads):
    	sleep(5)

    print('Over!')


if __name__ == '__main__':
    main()