import time
import datetime

from django import forms
from django.forms.util import ErrorDict
from django.conf import settings
from django.contrib.contenttypes.models import ContentType
from models import Comment
from django.utils.crypto import salted_hmac, constant_time_compare
from django.utils.encoding import force_unicode
from django.utils.hashcompat import sha_constructor
from django.utils.text import get_text_list
from django.utils.translation import ungettext, ugettext_lazy as _

COMMENT_MAX_LENGTH = getattr(settings,'COMMENT_MAX_LENGTH', 3000)

class CommentSecurityForm(forms.Form):
    """
    Handles the security aspects (anti-spoofing) for comment forms.
    """
    content_type  = forms.CharField(widget=forms.HiddenInput)
    object_pk     = forms.CharField(widget=forms.HiddenInput)
    timestamp     = forms.IntegerField(widget=forms.HiddenInput)
    security_hash = forms.CharField(min_length=40, max_length=40, widget=forms.HiddenInput)

    def __init__(self, target_object, data=None, initial=None):
        self.target_object = target_object
        if initial is None:
            initial = {}
        initial.update(self.generate_security_data())
        super(CommentSecurityForm, self).__init__(data=data, initial=initial)

    def security_errors(self):
        """Return just those errors associated with security"""
        errors = ErrorDict()
        for f in ["honeypot", "timestamp", "security_hash"]:
            if f in self.errors:
                errors[f] = self.errors[f]
        return errors

    def clean_security_hash(self):
        """Check the security hash."""
        security_hash_dict = {
            'content_type' : self.data.get("content_type", ""),
            'object_pk' : self.data.get("object_pk", ""),
            'timestamp' : self.data.get("timestamp", ""),
        }
        expected_hash = self.generate_security_hash(**security_hash_dict)
        actual_hash = self.cleaned_data["security_hash"]
        if not constant_time_compare(expected_hash, actual_hash):
            # Fallback to Django 1.2 method for compatibility
            # PendingDeprecationWarning <- here to remind us to remove this
            # fallback in Django 1.5
            expected_hash_old = self._generate_security_hash_old(**security_hash_dict)
            if not constant_time_compare(expected_hash_old, actual_hash):
                raise forms.ValidationError("Security hash check failed.")
        return actual_hash

    def clean_timestamp(self):
        """Make sure the timestamp isn't too far (> 2 hours) in the past."""
        ts = self.cleaned_data["timestamp"]
        if time.time() - ts > (2 * 60 * 60):
            raise forms.ValidationError("Timestamp check failed")
        return ts

    def generate_security_data(self):
        """Generate a dict of security data for "initial" data."""
        timestamp = int(time.time())
        security_dict =   {
            'content_type'  : str(self.target_object._meta),
            'object_pk'     : str(self.target_object._get_pk_val()),
            'timestamp'     : str(timestamp),
            'security_hash' : self.initial_security_hash(timestamp),
        }
        return security_dict

    def initial_security_hash(self, timestamp):
        """
        Generate the initial security hash from self.content_object
        and a (unix) timestamp.
        """

        initial_security_dict = {
            'content_type' : str(self.target_object._meta),
            'object_pk' : str(self.target_object._get_pk_val()),
            'timestamp' : str(timestamp),
          }
        return self.generate_security_hash(**initial_security_dict)

    def generate_security_hash(self, content_type, object_pk, timestamp):
        """
        Generate a HMAC security hash from the provided info.
        """
        info = (content_type, object_pk, timestamp)
        key_salt = "django.contrib.forms.CommentSecurityForm"
        value = "-".join(info)
        return salted_hmac(key_salt, value).hexdigest()

    def _generate_security_hash_old(self, content_type, object_pk, timestamp):
        """Generate a (SHA1) security hash from the provided info."""
        # Django 1.2 compatibility
        info = (content_type, object_pk, timestamp, settings.SECRET_KEY)
        return sha_constructor("".join(info)).hexdigest()

class CommentDetailsForm(CommentSecurityForm):
    """
    Handles the specific details of the comment (name, comment, etc.).
    """
    name          = forms.CharField(label=_("Name"), max_length=50)
    email         = forms.EmailField(label=_("Email address"))
    url           = forms.URLField(label=_("URL"), required=False)
    comment       = forms.CharField(label=_('Comment'), widget=forms.Textarea,
                                    max_length=COMMENT_MAX_LENGTH)

    def get_comment_object(self):
        """
        Return a new (unsaved) comment object based on the information in this
        form. Assumes that the form is already validated and will throw a
        ValueError if not.

        Does not set any of the fields that would come from a Request object
        (i.e. ``user`` or ``ip_address``).
        """
        if not self.is_valid():
            raise ValueError("get_comment_object may only be called on valid forms")

        CommentModel = self.get_comment_model()
        new = CommentModel(**self.get_comment_create_data())
        new = self.check_for_duplicate_comment(new)

        return new

    def get_comment_model(self):
        """
        Get the comment model to create with this form. Subclasses in custom
        comment apps should override this, get_comment_create_data, and perhaps
        check_for_duplicate_comment to provide custom comment models.
        """
        return Comment

    def get_comment_create_data(self):
        """
        Returns the dict of data to be used to create a comment. Subclasses in
        custom comment apps that override get_comment_model can override this
        method to add extra fields onto a custom comment model.
        """
        return dict(
            content_type = ContentType.objects.get_for_model(self.target_object),
            object_pk    = force_unicode(self.target_object._get_pk_val()),
            user_name    = self.cleaned_data["name"],
            user_email   = self.cleaned_data["email"],
            user_url     = self.cleaned_data["url"],
            comment      = self.cleaned_data["comment"],
            submit_date  = datetime.datetime.now(),
            site_id      = settings.SITE_ID,
            is_public    = True,
            is_removed   = False,
        )

    def check_for_duplicate_comment(self, new):
        """
        Check that a submitted comment isn't a duplicate. This might be caused
        by someone posting a comment twice. If it is a dup, silently return the *previous* comment.
        """
        possible_duplicates = self.get_comment_model()._default_manager.using(
            self.target_object._state.db
        ).filter(
            content_type = new.content_type,
            object_pk = new.object_pk,
            user_name = new.user_name,
            user_email = new.user_email,
            user_url = new.user_url,
        )
        for old in possible_duplicates:
            if old.submit_date.date() == new.submit_date.date() and old.comment == new.comment:
                return old

        return new

    def clean_comment(self):
        """
        If COMMENTS_ALLOW_PROFANITIES is False, check that the comment doesn't
        contain anything in PROFANITIES_LIST.
        """
        comment = self.cleaned_data["comment"]
        if settings.COMMENTS_ALLOW_PROFANITIES == False:
            bad_words = [w for w in settings.PROFANITIES_LIST if w in comment.lower()]
            if bad_words:
                plural = len(bad_words) > 1
                raise forms.ValidationError(ungettext(
                    "Watch your mouth! The word %s is not allowed here.",
                    "Watch your mouth! The words %s are not allowed here.", plural) % \
                    get_text_list(['"%s%s%s"' % (i[0], '-'*(len(i)-2), i[-1]) for i in bad_words], 'and'))
        return comment

class CommentForm(CommentDetailsForm):
    honeypot      = forms.CharField(required=False,
                                    label=_('If you enter anything in this field '\
                                            'your comment will be treated as spam'))

    def clean_honeypot(self):
        """Check that nothing's been entered into the honeypot."""
        value = self.cleaned_data["honeypot"]
        if value:
            raise forms.ValidationError(self.fields["honeypot"].label)
        return value
