import logging
import time
from functools import wraps
import json
import requests
from lxml import etree, html
from requests import HTTPError

search_list = []

if not hasattr(json, 'JSONDecodeError'):
    json.JSONDecodeError = ValueError

class RateLimitingError(HTTPError):
    pass


def retry(ExceptionToCheck, tries=4, delay=3, backoff=2, logger=None):
    """Retry calling the decorated function using an exponential backoff.

    http://www.saltycrane.com/blog/2009/11/trying-out-retry-decorator-python/
    original from: http://wiki.python.org/moin/PythonDecoratorLibrary#Retry

    :param ExceptionToCheck: the exception to check. may be a tuple of
        exceptions to check
    :type ExceptionToCheck: Exception or tuple
    :param tries: number of times to try (not retry) before giving up
    :type tries: int
    :param delay: initial delay between retries in seconds
    :type delay: int
    :param backoff: backoff multiplier e.g. value of 2 will double the delay
        each retry
    :type backoff: int
    :param logger: logger to use. If None, print
    :type logger: logging.Logger instance
    """

    def deco_retry(f):

        @wraps(f)
        def f_retry(*args, **kwargs):
            mtries, mdelay = tries, delay
            while mtries > 1:
                try:
                    return f(*args, **kwargs)
                except ExceptionToCheck as e:
                    msg = "%s, Retrying in %d seconds..." % (str(e), mdelay)
                    if logger:
                        logger.warning(msg)
                    else:
                        print(msg)
                    time.sleep(mdelay)
                    mtries -= 1
                    mdelay *= backoff
            return f(*args, **kwargs)

        return f_retry  # true decorator

    return deco_retry


def fetch_all_searx_engines():
    # error handling is for pussies
    tree = etree.XML(
        requests.get("http://stats.searx.oe5tpo.com").content,
        parser=html.HTMLParser()
    )
    searxes = [str(x) for x in tree.xpath('//span[text()[contains(.,"200 - OK")]]/../..//a/text()')]

    return searxes


@retry(ExceptionToCheck=(RateLimitingError, json.JSONDecodeError))
def searx(text):
    global search_list
    if not search_list:
        search_list = fetch_all_searx_engines()
    logger = logging.getLogger(__name__)

    url = search_list[-1]
    logger.info('Currently feeding from {} (of {} in stock)'.format(url, len(search_list)))
    response = requests.get(url, params={
        'q': text,
        'format': 'json',
        'lang': 'de'
    })
    if response.status_code == 429:
        search_list.pop()
        raise RateLimitingError(response=response, request=response.request)
    try:
        response = response.json()
    except json.JSONDecodeError:
        # "maintenance" they say...
        search_list.pop()
        raise

    if not response['results']:
        return
    return [(r['content'], r['url']) for r in response['results']][0]