import w3lib.url
import w3lib.html

from lxml import etree
import re
from hashlib import md5

from feedgenerator import Rss201rev2Feed, Enclosure
import datetime

import MySQLdb
from settings import DATABASES, DOWNLOADER_USER_AGENT

url_hash_regexp = re.compile('(#.*)?$')

def element_to_string(element):
    s = [element.text] if element.text else []
    for sub_element in element:
        s.append(etree.tostring(sub_element))
    if element.tail:    
        s.append(element.tail)
    return ''.join(s)

def _build_link(html, doc_url, url):
    base_url = w3lib.html.get_base_url(html, doc_url)
    return w3lib.url.urljoin_rfc(base_url, url)

def buildFeed(response, feed_config):
    response.selector.remove_namespaces()

    tree = response.selector._root.getroottree()

    # get data from html 
    items = []
    for node in tree.xpath(feed_config['xpath']):
        item = {}
        title_link = None
        for field_name in ['title', 'description']:
            if field_name in feed_config['fields']:
                element = node.xpath(feed_config['fields'][field_name])
                if element:
                    item[field_name] = element_to_string(element[0])
                    # get item link
                    if field_name == 'title':
                        anchor = element[0].xpath('ancestor-or-self::node()[name()="a"]')
                        if anchor and anchor[0].get('href'):
                            title_link = _build_link(response.body_as_unicode(), feed_config['uri'], anchor[0].get('href'))
                  
        if len(item) == len(feed_config['fields']): # all fields are required
            item['title_link'] = title_link
            items.append(item)
    
    title = response.selector.xpath('//title/text()').extract()

    #build feed
    feed = Rss201rev2Feed(
        title = title[0] if title else 'Polite Pol: ' + feed_config['uri'],
        link=feed_config['uri'],
        description="Generated by PolitePol.com.\n"+\
            "Source page url: " + feed_config['uri'],
        language="en",
    )
    for item in items:
        title = item['title'] if 'title' in item else ''
        desc = item['description'] if 'description' in item else ''
        if item['title_link']: 
            link = item['title_link']
        else:
            link = url_hash_regexp.sub('#' + md5((title+desc).encode('utf-8')).hexdigest(), feed_config['uri'])
        feed.add_item(
            title = title,
            link = link,
            description = desc,
            #enclosure=Enclosure(fields[4], "32000", "image/jpeg") if  4 in fields else None, #"Image"
            pubdate=datetime.datetime.now()
        )
    return feed.writeString('utf-8')

def getFeedData(request, feed_id):
    # get url, xpathes
    creds = DATABASES['default']
    db = MySQLdb.connect(host=creds['HOST'], port=int(creds['PORT']), user=creds['USER'], passwd=creds['PASSWORD'], db=creds['NAME'])
    feed = {}
    with db:
        cur = db.cursor()
        cur.execute("""select f.uri, f.xpath, fi.name, ff.xpath from frontend_feed f
                       right join frontend_feedfield ff on ff.feed_id=f.id
                       left join frontend_field fi on fi.id=ff.field_id
                       where f.id=%s""", (feed_id,))
        rows = cur.fetchall()

        for row in rows:
            if not feed:
                feed['uri'] = row[0]
                feed['xpath'] = row[1]
                feed['fields'] = {}
            feed['fields'][row[2]] = row[3]

    if feed:
        return [feed['uri'], feed]
    else:
        return 'Feed generator error: config of feed is empty'