import inspect
from django.utils.html import strip_tags
from django.utils.encoding import force_unicode

def process_docstring(app, what, name, obj, options, lines):
    # This causes import errors if left outside the function
    from django.db import models

    # Only look at objects that inherit from Django's base model class
    if inspect.isclass(obj) and issubclass(obj, models.Model):
        # Grab the field list from the meta class
        fields = obj._meta.fields
    
        for field in fields:
            # Decode and strip any html out of the field's help text
            help_text = strip_tags(force_unicode(field.help_text))
            
            # Decode and capitalize the verbose name, for use if there isn't
            # any help text
            verbose_name = force_unicode(field.verbose_name).capitalize()
            
            if help_text:
                # Add the model field to the end of the docstring as a param
                # using the help text as the description
                lines.append(u':param %s: %s' % (field.attname, help_text))
            else:
                # Add the model field to the end of the docstring as a param
                # using the verbose name as the description
                lines.append(u':param %s: %s' % (field.attname, verbose_name))

            # Add the field's type to the docstring
            if isinstance(field, models.ForeignKey):
                to = field.rel.to
                lines.append(u':type %s: %s to :class:`~%s.%s`' % (field.attname, type(field).__name__, to.__module__, to.__name__))

            else:
                lines.append(u':type %s: %s' % (field.attname, type(field).__name__)) 
    
    # Return the extended docstring
    return lines