from ..engine import SearchEngine
from ..config import PROXY, TIMEOUT, FAKE_USER_AGENT
from ..utils import unquote_url


class Google(SearchEngine):
    '''Searches google.com'''
    def __init__(self, proxy=PROXY, timeout=TIMEOUT):
        super(Google, self).__init__(proxy, timeout)
        self._base_url = 'https://www.google.com'
        self._delay = (2, 6)
        self.set_headers({'User-Agent':FAKE_USER_AGENT})
    
    def _selectors(self, element):
        '''Returns the appropriate CSS selector.'''
        selectors = {
            'url': 'a[href]', 
            'title': 'a', 
            'text': 'span.st', 
            'links': 'div#search div[class=g]', 
            'next': 'div#foot a#pnnext'
        }
        return selectors[element]
    
    def _first_page(self):
        '''Returns the initial page and query.'''
        url = u'{}/search?q={}'.format(self._base_url, self._query)
        return {'url':url, 'data':None}
    
    def _next_page(self, tags):
        '''Returns the next page URL and post data (if any)'''
        selector = self._selectors('next')
        next_page = self._get_tag_item(tags.select_one(selector), 'href')
        url = (self._base_url + next_page) if next_page else None
        return {'url':url, 'data':None}

    def _get_url(self, tag, item='href'):
        '''Returns the URL of search results item.'''
        selector = self._selectors('url')
        url = self._get_tag_item(tag.select_one(selector), item)

        if url.startswith(u'/url?q='):
            url = url.replace(u'/url?q=', u'').split(u'&sa=')[0]
        return unquote_url(url)

