"""Simple captcha library, based on PIL. Monkey patch functions in this module

if you want something better...

:organization: Logilab

:copyright: 2009-2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.

:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr

:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses

"""

__docformat__ = "restructuredtext en"

from random import randint, choice

from cStringIO import StringIO

import Image, ImageFont, ImageDraw, ImageFilter

from time import time

from cubicweb import tags

from cubicweb.view import StartupView

from cubicweb.web import httpcache, formwidgets as fw, formfields as ff

def pil_captcha(text, fontfile, fontsize):

    """Generate a captcha image. Return a PIL image object.

    adapted from http://code.activestate.com/recipes/440588/

    """

    # randomly select the foreground color

    fgcolor = randint(0, 0xffff00)

    # make the background color the opposite of fgcolor

    bgcolor = fgcolor ^ 0xffffff

    # create a font object

    font = ImageFont.truetype(fontfile, fontsize)

    # determine dimensions of the text

    dim = font.getsize(text)

    # create a new image slightly larger that the text

    img = Image.new('RGB', (dim[0]+5, dim[1]+5), bgcolor)

    draw = ImageDraw.Draw(img)

    # draw 100 random colored boxes on the background

    x, y = img.size

    for num in range(100):

        draw.rectangle((randint(0, x), randint(0, y),

                        randint(0, x), randint(0, y)),

                       fill=randint(0, 0xffffff))

    # add the text to the image

    draw.text((3, 3), text, font=font, fill=fgcolor)

    img = img.filter(ImageFilter.EDGE_ENHANCE_MORE)

    return img

def captcha(fontfile, fontsize, size=5, format='JPEG'):

    """Generate an arbitrary text, return it together with a buffer containing

    the captcha image for the text

    """

    text = u''.join(choice('QWERTYUOPASDFGHJKLZXCVBNM') for i in range(size))

    img = pil_captcha(text, fontfile, fontsize)

    out = StringIO()

    img.save(out, format)

    out.seek(0)

    return text, out

class CaptchaView(StartupView):

    __regid__ = 'captcha'

    http_cache_manager = httpcache.NoHTTPCacheManager

    binary = True

    templatable = False

    content_type = 'image/jpg'

    def call(self):

        text, data = captcha.captcha(self._cw.vreg.config['captcha-font-file'],

                                     self._cw.vreg.config['captcha-font-size'])

        self._cw.set_session_data('captcha', text)

        self.w(data.read())

class CaptchaWidget(fw.TextInput):

    def render(self, form, field, renderer=None):

        # t=int(time()*100) to make sure img is not cached

        src = form._cw.build_url('view', vid='captcha', t=int(time()*100))

        img = tags.img(src=src, alt=u'captcha')

        img = u'<div class="captcha">%s</div>' % img

        return img + super(CaptchaWidget, self).render(form, field, renderer)