import os, re, random
from django import template
from django.conf import settings

register = template.Library()

def random_pic(parser, token):
    try:
        tag_name, dir_name = token.split_contents()
    except ValueError:
        raise template.TemplateSyntaxError, "%r tag requires a single argument" % token.contents.split()[0]
    if not (dir_name[0] == dir_name[-1] and dir_name[0] in ('"', "'")):
        raise template.TemplateSyntaxError, "%r tag's argument should be in quotes" % tag_name
    return RandomPicNode(dir_name[1:-1])

class RandomPicNode(template.Node):
    def __init__(self, dir_name):
        self.dir_name = dir_name

    def filter(self, filelist):
        regex = re.compile(r'(\.jp[e]*g|\.png|\.gif)', re.I)
        return [pic for pic in filelist if re.search(regex, pic)]

    def render(self, context):
        try:
            pics = self.filter(os.listdir(os.path.join(settings.MEDIA_ROOT, self.dir_name)))
            filename = random.choice(pics)
        except: return ""
        return os.path.join(settings.MEDIA_URL, self.dir_name, filename)
register.tag(random_pic)