From 36e1f7693f5f1a4ec565086f20f1e78c536481cd Mon Sep 17 00:00:00 2001
From: Simon Weald <simon@simonweald.com>
Date: Wed, 12 Sep 2018 22:54:12 +0100
Subject: [PATCH] initial foray into asynchronous crawling

---
 async_crawler.py | 74 +++++++++++++++++++++++++++++++++++++++++
 utils/helpers.py | 85 +++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 155 insertions(+), 4 deletions(-)
 create mode 100644 async_crawler.py

diff --git a/async_crawler.py b/async_crawler.py
new file mode 100644
index 0000000..5b48b3e
--- /dev/null
+++ b/async_crawler.py
@@ -0,0 +1,74 @@
+#!/usr/bin/env python
+'''
+Need a docstring.
+'''
+
+import argparse
+import jinja2
+import os
+import asyncio
+from datetime import datetime
+# from utils.helpers import (UrlPool, WebPage, RobotsTxt, sanitise_url)
+from utils.helpers import RobotsTxt, AsyncCrawler, sanitise_url
+
+
+def init_crawler(url=None):
+    '''
+    docstring
+    '''
+    # ensure we have a sensible URL to work with
+    baseurl = sanitise_url(url=url, base_url=True)
+    # get robots.txt
+    robots = RobotsTxt(base_url=baseurl)
+
+    return(baseurl, robots)
+
+
+def render_sitemap(base_url=None, crawled_urls=None, runtime=None):
+    '''
+    Renders the sitemap as an HTML file.
+    '''
+    # urlcount = len(crawled_urls)
+    # sorted_urls = sorted(crawled_urls)
+
+    tmpl = jinja2.Environment(
+        loader=jinja2.FileSystemLoader('templates')
+    ).get_template('sitemap.html.j2')
+
+    rendered_html = tmpl.render(
+        base_url=base_url, urlcount=urlcount, urls=sorted_urls, runtime=runtime)
+
+    with open('sitemap.html', 'w') as outfile:
+        outfile.write(rendered_html)
+
+    print('Sitemap available at {0}/sitemap.html'.format(os.getcwd()))
+
+
+def main(args=None):
+    '''
+    docstring
+    '''
+    starttime = datetime.now()
+
+    baseurl, robots = init_crawler(url=args.url)
+
+    # create a crawler
+    async_crawler = AsyncCrawler(baseurl=baseurl, robots=robots, concurrency=args.concurrency)
+    # async_crawler.run()
+
+    crawler = asyncio.Task(async_crawler.run())
+    loop = asyncio.get_event_loop()
+    loop.run_until_complete(crawler)
+    loop.close()
+    result = crawler.result()
+    print(len(result))
+
+
+if __name__ == '__main__':
+
+    parser = argparse.ArgumentParser(description='Recursive web crawler')
+    parser.add_argument("-u", "--url", required=True, help="Base url to crawl")
+    parser.add_argument("-s", "--concurrency", required=False, type=int, default=50, help="Max number of pages to crawl concurrently")
+    args = parser.parse_args()
+
+    main(args)
diff --git a/utils/helpers.py b/utils/helpers.py
index 8da18f0..05cc85c 100644
--- a/utils/helpers.py
+++ b/utils/helpers.py
@@ -3,13 +3,90 @@
 Utilities to provide various misc functions.
 '''
 
-from bs4 import BeautifulSoup
-import aiohttp
 import urllib.request
-import urllib.robotparser
 import urllib.error
 import gzip
-from urllib.parse import (urljoin, urlsplit)
+
+
+
+import aiohttp
+import asyncio
+from bs4 import BeautifulSoup
+from urllib.parse import urljoin, urlsplit
+import urllib.robotparser
+
+
+class AsyncCrawler(object):
+    '''
+    docstring
+    '''
+
+    def __init__(self, baseurl=None, robots=None, concurrency=None):
+        self.baseurl = baseurl
+        self.robots = robots
+        self.uncrawled = set()
+        self.crawled = set()
+        self.session = aiohttp.ClientSession()
+        self.semaphore = asyncio.BoundedSemaphore(concurrency)
+        # add the base URL to be crawled
+        self.uncrawled.add(baseurl)
+        self.headers = {'Accept-Encoding': 'gzip, deflate',
+                        'User-Agent': 'Mozilla/5.0 (X11; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0'}
+
+
+    def validate_url(self, url):
+        '''
+        Checks if the discovered URL is local to the base URL.
+        '''
+        # ensure the URL is in a sane format
+        url = sanitise_url(url=url)
+
+        if url.startswith(self.baseurl) and robots.check(url=url):
+            return url
+        else:
+            return False
+
+
+    def get_source(self, url):
+        '''
+        Obtains the page's source.
+        '''
+        pass
+
+        return source
+
+
+    def find_links(self, source):
+        '''
+        Find all links in a page's source.
+        '''
+        links = set()
+
+        html = BeautifulSoup(source, 'lxml')
+        hrefs = html.find_all('a', href=True)
+
+        for href in hrefs:
+            url = self.validate_url(url=href)
+            if url:
+                links.add(url)
+
+        return links
+
+
+    def run(self):
+        '''
+        function which runs the crawler
+        '''
+        pass
+
+        for url in self.uncrawled:
+            validated = validate_url(url=url)
+
+            if validated:
+                source = get_source(url=url)
+                links = find_links(source=source)
+
+
 
 
 class UrlPool(object):