[enh] yandex engine added

"""

 Yahoo (Web)

 @website     https://yandex.ru/

 @provide-api ?

 @using-api   no

 @results     HTML (using search portal)

 @stable      no (HTML can change)

 @parse       url, title, content

"""

from urllib import urlencode

from lxml import html

from searx.search import logger

logger = logger.getChild('yandex engine')

# engine dependent config

categories = ['general']

paging = True

language_support = True  # TODO

# search-url

base_url = 'https://yandex.ru/'

search_url = 'search/?{query}&p={page}'

results_xpath = '//div[@class="serp-item serp-item_plain_yes clearfix i-bem"]'

url_xpath = './/h2/a/@href'

title_xpath = './/h2/a//text()'

content_xpath = './/div[@class="serp-item__text"]//text()'

def request(query, params):

    params['url'] = base_url + search_url.format(page=params['pageno']-1,

                                                 query=urlencode({'text': query}))

    return params

# get response from search-request

def response(resp):

    dom = html.fromstring(resp.text)

    results = []

    for result in dom.xpath(results_xpath):

        try:

            res = {'url': result.xpath(url_xpath)[0],

                   'title': ''.join(result.xpath(title_xpath)),

                   'content': ''.join(result.xpath(content_xpath))}

        except:

            logger.exception('yandex parse crash')

            continue

        results.append(res)

    return results

    engine : yahoo

    shortcut : yh

  - name : yandex

    engine : yandex

    shortcut : ya

    disabled : True

  - name : yahoo news

    engine : yahoo_news

    shortcut : yhn