"""
Human verification system for the comments plugin.
Based on a idea and ref impl of Jesus Roncero Franco <jesus at roncero.org>.
Implemented as a pyblosxom plugin by Steven Armstrong <sa at c-area.ch>.

Creates a random number, generates an image of it, and stores the number
in the session. Then compares the number the user entered in the comment
form with the one stored in the session. Rejects the comment if they 
don't match.

If you make any changes to this plugin, please send a patch to 
<sa+pyblosxom at c-area dot ch> so I can incorporate them.
Thanks!


Thanks to Ludger Humbert for pointing out issues with different PIL versions.
Thanks to Lance Levsen for adding the allow_trackback bypass and fixing some bugs.


To install:
1) Put nospam.py in your plugin directory.
2) In config.py add nospam to py['load_plugins']
3) Add the following variables to config.py:
    py['nospam_font'] = '/path/to/truetype/font.ttf' # required, no default
    py['nospam_extension'] = '/nospam.png' # optional, this is the default
    py['nospam_allow_trackback'] = 1 # optional to allow trackbacks to pass
                               # through when using the trackback
                               # plugin from Ted Leung
    
Note:
If you get an error about problems with TrueType fonts, it's likely that
you are using an older PIL version that can't handle them.
In this case you'll have to use a pil font from [1] instead and configure config.py as:
    py['nospam_font'] = '/path/to/pilfonts/lubB10.pil'

[1] http://effbot.org/pil/pilfonts.zip


Add something like this to your comment-form.html template:
<label for="nospam">Secret Number:</label>
<img src="$base_url/nospam.png" alt="Secret Number Image" title="Type this number into the field on the right" />
<input name="nospam" id="nospam" type="text" value="" maxlength="5" style="width:5em" />


Dependecies:
    - My compatibility plugin if you're not using pyblosxom 1.2+.
    - My session plugin.
    - Python imaging library from http://www.pythonware.com/products/pil/


$Id: nospam.py,v 1.6 2006/04/14 18:12:17 sar Exp $
"""
__author__ = "Steven Armstrong <sa at c-area dot ch>"
__version__ = "$Revision: 1.6 $ $Date: 2006/04/14 18:12:17 $"
__url__ = "http://www.c-area.ch/code/"
__description__ = "Human verification system for the comments plugin"
__license__ = "GPL 2+"


# Python imports
import sys
import os
import random
from Pyblosxom import tools

# PIL imports http://www.pythonware.com/products/pil/
try: # use try/except so verify_installation can guide the user how to setup PIL
    import Image
    import ImageDraw
    import ImageOps
    try:
        import ImageFont
    except ImportError:
        import PIL.ImageFont as ImageFont
except ImportError:
    pass

# parameters
_xstep = 5 
_ystep = 5 
_imageSize = (61,21)
_bgColor = (255,255,255) # White
_gridInk = (200,200,200)
_fontInk = (130,130,130)
_fontSize = 14
# set in cb_start callback
_fontPath = None

# the names of the fields used in the comment form
_form_fields = ["title", "author", "email", "url", "body"]


def verify_installation(request):
    config = request.getConfiguration()
    retval = 1

    from Pyblosxom import pyblosxom
    version = pyblosxom.VERSION
    if version < 1.2:
        try:
            import compatibility
        except ImportError:
            print "You're running Pyblosxom %.1f and will need " % version
            print "the 'compatibility.py' plugin to use this plugin."
            retval = 0

    try:
        import session
    except ImportError:
        print "Missing required plugin 'session.py'."
        retval = 0

    old_pil = False
    no_pil = False
    try:
        import ImageFont
    except ImportError:
        old_pil = True
        try:
            import PIL.ImageFont
        except ImportError:
            no_pil = True

    if not config.has_key('nospam_font'):
        print "Missing required property: 'nospam_font'"
        print "This must be the absolute path to a truetype font."
        retval = 0

    if no_pil:
        print "Python imaging library not found."
        print "Get and install it from http://www.pythonware.com/products/pil/"
        retval = 0

    if old_pil:
        print "You seem to be using an old PIL (Python imaging library) version."
        print "You must get a pil font from http://effbot.org/pil/pilfonts.zip"
        print "and point the 'nospam_font' config property to one of them."

    if not config.has_key('nospam_extension'):
        print "Missing optional property: 'nospam_extension'"
        print "Using the default of '/nospam.png'"

    if not config.has_key('nospam_allow_trackback'):
        print "Missing optional property: 'nospam_allow_trackback'"
        print "Using the default of 0"
    
    return retval


# This function is (c) Jesus Roncero Franco <jesus at roncero.org>.
# Modified to support old and new PIL versions by Steven Armstrong.
def _generateImage(number):
    try:
        # recent PIL version with support for truetype fonts
        font = ImageFont.truetype(_fontPath, _fontSize)
    except AttributeError:
        # old PIL version, fallback to pil fonts
        font = ImageFont.load(_fontPath)

    img = Image.new("RGB", _imageSize, _bgColor)
    draw = ImageDraw.Draw(img)
    
    xsize, ysize = img.size

    # Do we want the grid start at 0,0 or want some offset?
    x, y = 0,0
    
    while x <= xsize:
        try:
            # recent PIL version
            draw.line(((x, 0), (x, ysize)), fill=_gridInk)
        except TypeError:
            # old PIL version
            draw.setink(_gridInk)
            draw.line(((x, 0), (x, ysize)))
        x = x + _xstep 
    while y <= ysize:
        try:
            draw.line(((0, y), (xsize, y)), fill=_gridInk)
        except TypeError:
            draw.setink(_gridInk)
            draw.line(((0, y), (xsize, y)))
        y = y + _ystep 
    
    try:
        draw.text((10, 2), number, font=font, fill=_fontInk)
    except TypeError:
        draw.setink(_fontInk)
        draw.text((10, 2), number, font=font)

    return img


def _writeImage(request):
    number = str(random.randrange(1,99999,1))

    session = request.getSession()
    session["nospam"] = number
    session.save()

    image = _generateImage(number)

    response = request.getResponse()
    response.addHeader('Content-Type', 'image/png')
    image.save(response, "PNG")


def _remember_comment(request):
    """
    Stores form fields in the data dict so they can be used to 
    refill the form in the template.
    
    @param request: pyblosxom request object
    @type request: L{Pyblosxom.pyblosxom.Request}
    """
    data = request.getData()
    form = request.getForm()
    for key in _form_fields:
        data["cmt_%s" % key] = (form.has_key(key) and [form[key].value] or [''])[0]


def _forget_comment(request):
    """
    Resets/forgets any stored form field values.
    
    @param request: pyblosxom request object
    @type request: L{Pyblosxom.pyblosxom.Request}
    """
    data = request.getData()
    for key in _form_fields:
        key = "cmt_%s" % key
        if key in data:
            del data[key]



#******************************
# Callbacks
#******************************

def cb_start(args):
    request = args['request']
    config = request.getConfiguration()
    global _fontPath
    _fontPath = config.get('nospam_font')


def cb_handle(args):
    request = args['request']
    http = request.getHttp()
    config = request.getConfiguration()
    ext = config.get("nospam_extension", "/nospam.png")
    if http['PATH_INFO'].endswith( ext ):
        # write the image to the output stream
        _writeImage(request)
        # return True to tell pyblosxom that the request has been taken care of
        return 1


def cb_comment_reject(args):
    """
    Checks if the the nospam number of the incomming request 
    matches the one stored in the session.
    Creates a template variable $cmt_nospam_error with a 
    error message if it didn't.
    
    Also creates the following template variables:
    $cmt_title, $cmt_author, $cmt_email, $cmt_url, $cmt_body
    which can be used to populate the form with the values
    provided by the user.

    If the config setting nospam_allow_trackback is True, 
    and the comment came in via the trackback plugin the comment is accepted.
    
    @param args: a dict containing: pyblosxom request, comment dict 
    @type config: C{dict}
    @return: True if the comment should be rejected, False otherwise
    @rtype: C{bool}
    """
    request = args['request']
    session = request.getSession()
    form = request.getForm()
    data = request.getData()
    config = request.getConfiguration()
    allow_trackback = config.get('nospam_allow_trackback', 0)
    
    try:
        nospam = int(form["nospam"].value)
        sess_nospam = int(session["nospam"])
    except:
        nospam = 0
        sess_nospam = 1

    if allow_trackback:
        comment = args['comment']
        #log = tools.getLogger()
        #log.info(comment['author'])
        if comment['author'].count("Trackback") > 0:
            return False
        
    if nospam != sess_nospam:
        _remember_comment(request)
        data["cmt_nospam_error"] = "Secret number did not match."
        return True
    else:
        _forget_comment(request)
        if "cmt_nospam_error" in data:
            del data["cmt_nospam_error"]
        return False