[enh] yahoo engine added

#!/usr/bin/env python

from urllib import urlencode

from searx.engines.xpath import extract_text, extract_url

from lxml import html

categories = ['general']

search_url = 'http://search.yahoo.com/search?{query}&b={offset}'

results_xpath = '//div[@class="res"]'

url_xpath = './/h3/a/@href'

title_xpath = './/h3/a'

content_xpath = './/div[@class="abstr"]'

suggestion_xpath = '//div[@id="satat"]//a'

paging = True

def request(query, params):

    offset = (params['pageno'] - 1) * 10 + 1

    params['url'] = search_url.format(offset=offset,

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

    print params['url']

    return params

def response(resp):

    results = []

    dom = html.fromstring(resp.text)

    for result in dom.xpath(results_xpath):

        url = extract_url(result.xpath(url_xpath), search_url)

        title = extract_text(result.xpath(title_xpath)[0])

        content = extract_text(result.xpath(content_xpath)[0])

        results.append({'url': url, 'title': title, 'content': content})

    if not suggestion_xpath:

        return results

    for suggestion in dom.xpath(suggestion_xpath):

        results.append({'suggestion': extract_text(suggestion)})

    return results