#!/usr/bin/python

# Protip: want to monitor a thread and download all new images every 5 seconds?
# while x=0; do 4c [-nf] url; sleep 5; done

import re, urllib, urllib2, argparse, os

parser = argparse.ArgumentParser(description='Downloads all full-size images in an arbitrary 4chan thread.')

parser.add_argument('urllist', metavar='url', type=str, nargs='+',
                   help='the URL of the thread')
parser.add_argument('-n', '--newdir', dest='newdir', action='store_true',
                   help='create a new directory for this thread in the current directory')
parser.add_argument('-f', '--force', dest='force_redownload', action='store_true',
                   help='force redownloading every image, overwriting it if it already exists')
                   
args = parser.parse_args()
options = vars(args)

regex = 'href="(\/\/images\.4chan\.org\/b\/src\/[0-9]+\.[a-z]+)"'

for url in options['urllist']:
	print "Thread URL: %s" % url
	
	try:
		page = urllib2.urlopen(url).read()
	except ValueError:
		print "That does not look like a valid URL."
		exit(1)
	except urllib2.HTTPError:
		print "The given URL returns a HTTP 404 status code - the thread may have died."
		exit(1)

	if options['newdir'] == True:
		thread_id = url.split('/')[-1]
		target_dir = "%s/" % thread_id

		if not os.path.exists(thread_id):
			os.makedirs(thread_id)
	else:
		target_dir = ""

	search = re.compile(regex)
	matches = search.finditer(page)

	urls = []

	for match in matches:
		if match.group(1) not in urls:
			urls.append(match.group(1))

	current = 1
	total = len(urls)

	print "  Parsed thread. Total images: %d" % total

	for downloadurl in urls:
		downloadurl = "http:%s" % downloadurl
		filename = downloadurl.split('/')[-1]
		path = target_dir + filename
		
		if os.path.exists(path) and options['force_redownload'] == False:
			print "Skipped existing file %s (%d/%d)." % (filename, current, total)
		else:
			urllib.urlretrieve(downloadurl, path)
			print "Downloaded %s (%d/%d)." % (filename, current, total)
		current += 1
	
	print "Done."