#!/usr/bin/python3
from threading import Thread, active_count
from requests import Session, utils
from lxml import html
from re import compile, findall
from os import makedirs
from os.path import exists, getmtime
from calendar import timegm
from time import strptime, sleep
from urllib.parse import unquote

NUM_THREADS = 5  # max number of threads

def create_filepath(filepath):
    if not exists(filepath):
        makedirs(filepath)


def download_files(session, f):
    filename = f[1] + utils.unquote(f[0])[utils.unquote(f[0]).rindex('/'):]
    if not exists(filename):
        response = session.get(f[0], allow_redirects=False)
        if response.status_code == 301:
            download_files(session, (response.headers['Location'], f[1]))
        elif response.status_code == 200:
            create_filepath(f[1])
            with open(filename, 'wb') as fd:
                for chunk in response.iter_content(1024):
                    fd.write(chunk)
            print('[+] ' + filename)
    else:
        response = session.head(f[0], allow_redirects=False)
        if response.status_code == 301:
            download_files(session, (response.headers['Location'], f[1]))
        elif response.status_code == 200:
            last_mod_file = getmtime(filename)
            try:
                last_mod_www = timegm(strptime(response.headers['Last-Modified'], '%a, %d %b %Y %H:%M:%S %Z'))
            except KeyError:
                print('Can\'t check {} for updates.'.format(f[0]))
                last_mod_www = last_mod_file

            if last_mod_www > last_mod_file:
                response = session.get(f[0])
                if response.status_code == 200:
                    create_filepath(f[1])
                    with open(filename, 'wb') as fd:
                        for chunk in response.iter_content(1024):
                            fd.write(chunk)
                    print('[M] ' + filename)


def resolve_direct_links(session, hrefs):
    links = []
    for href in hrefs:
        tmp = session.head(href).headers
        if 'Location' in tmp:
            links.append(tmp['Location'])
    return links

def resolve_direct_link(session, href):
    return resolve_direct_links(session, [href])[0]


def get_links_from_folder(session, urls):
    hrefs = []
    for url in urls:
        response = session.get(url)
        hrefs += findall(compile(
            'https\:\/\/www\.moodle\.tum\.de\/pluginfile\.php\/\d+\/mod_folder\/content\/0\/(?:[\w\d\_\-]*\/)*[\w\d\_\-\.]+'),
                         response.text)
    return hrefs

def get_link_from_folder(session, url):
    return get_links_from_folder(session, [url])[0]

def get_file_links(session, url, files):
    links = []

    response = session.get(url)

    hrefs = html.fromstring(response.text).xpath('//a/@href')
    for i in range(0, len(hrefs)):
        href = hrefs[i]
        if 'moodle.tum.de/mod/resource/view.php' in href:
            hrefs[i] = resolve_direct_link(session, href)
        if 'moodle.tum.de/mod/folder/view.php' in href:
            hrefs[i] = get_link_from_folder(session, href)
    hrefs = [href.replace('?forcedownload=1', '') for href in hrefs]

    # ---------------

    url = url.replace('index.html.en','').replace('index.html.de','')

    for f in files:
        reg = compile(f[0])
        for href in hrefs:
            match = reg.findall(unquote(href))
            if match:
                if not ('https://' in href or 'http://' in href):
                    links.append((url + href, f[1]))
                else:
                    links.append((href, f[1]))

    return links


def establish_moodle_session(user, passwd):
    session = Session()

    response = session.get('https://www.moodle.tum.de')
    response = session.get('https://www.moodle.tum.de/Shibboleth.sso/Login?providerId=https://tumidp.lrz.de/idp/shibboleth&target=https://www.moodle.tum.de/auth/shibboleth/index.php')
    response = session.post('https://tumidp.lrz.de/idp/profile/SAML2/Redirect/SSO?execution=e1s1', data={'j_username': user, 'j_password': passwd, '_eventId_proceed':''})

    parsed = html.fromstring(response.text)

    session.post('https://www.moodle.tum.de/Shibboleth.sso/SAML2/POST',
                 data={'RelayState': parsed.forms[0].fields['RelayState'],
                       'SAMLResponse': parsed.forms[0].fields['SAMLResponse']})

    return session

def main(url, files, user='', passwd=''):
    # create session
    if 'www.moodle.tum.de' in url:
        session = establish_moodle_session(user, passwd)
    else:
        session = Session()
        session.auth = (user, passwd)
        session.headers = {
            "Accept-Language": "en-US,en;"
        }

    # get file links
    links = get_file_links(session, url, files)

    # download files
    worker = []
    for l in links:
        while active_count() > NUM_THREADS:
            sleep(0.1)
        worker.append(Thread(target=download_files, args=(session, l)).start())

    [t.join() for t in worker if t]