import datetime
import time
import sys
from utils import feedfinder

def encode(tstr):
    """ Encodes a unicode string in utf-8
    """
    if not tstr:
        return ''
    # this is _not_ pretty, but it works
    try:
        return tstr.encode('utf-8', "xmlcharrefreplace")
    except UnicodeDecodeError:
        # it's already UTF8.. sigh
        return tstr.decode('utf-8').encode('utf-8')

def prints(tstr):
    """ lovely unicode
    """
    sys.stdout.write('%s\n' % (tstr.encode(sys.getdefaultencoding(),
                         'replace')))
    sys.stdout.flush()

def mtime(ttime):
    """ datetime auxiliar function.
    """
    return datetime.datetime.fromtimestamp(time.mktime(ttime))

# From: http://www.poromenos.org/node/87
def levenshtein_distance(first, second):
    """Find the Levenshtein distance between two strings."""
    if len(first) > len(second):
        first, second = second, first
    if len(second) == 0:
        return len(first)
    first_length = len(first) + 1
    second_length = len(second) + 1
    distance_matrix = [[0] * second_length for x in range(first_length)]
    for i in range(first_length):
       distance_matrix[i][0] = i
    for j in range(second_length):
       distance_matrix[0][j]=j
    for i in xrange(1, first_length):
        for j in range(1, second_length):
            deletion = distance_matrix[i-1][j] + 1
            insertion = distance_matrix[i][j-1] + 1
            substitution = distance_matrix[i-1][j-1]
            if first[i-1] != second[j-1]:
                substitution += 1
            distance_matrix[i][j] = min(insertion, deletion, substitution)
    return distance_matrix[first_length-1][second_length-1]
    
    
def fetch_address_from_page(url, existing_feed=None):
    from apps.rss_feeds.models import Feed
    feed_finder_url = feedfinder.feed(url)
    if feed_finder_url:
        if existing_feed:
            existing_feed.feed_address = feed_finder_url
            existing_feed.save()
            feed = existing_feed
        else:
            try:
                feed = Feed.objects.get(feed_address=feed_finder_url)
            except Feed.DoesNotExist:
                feed = Feed(feed_address=feed_finder_url)
                feed.save()
                feed.update()
        return feed