from django import oldforms, template
from django.conf import settings
from django.contrib.admin.filterspecs import FilterSpec
from django.contrib.admin.views.decorators import staff_member_required
from django.views.decorators.cache import never_cache
from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import ImproperlyConfigured, ObjectDoesNotExist, PermissionDenied
from django.core.paginator import QuerySetPaginator, InvalidPage
from django.shortcuts import get_object_or_404, render_to_response
from django.db import models
from django.db.models.query import QuerySet
from django.http import Http404, HttpResponse, HttpResponseRedirect
from django.utils.html import escape
from django.utils.text import capfirst, get_text_list
from django.utils.encoding import force_unicode, smart_str
from django.utils.translation import ugettext as _
from django.utils.safestring import mark_safe
import operator

try:
    set
except NameError:
    from sets import Set as set   # Python 2.3 fallback

from django.contrib.admin.models import LogEntry, ADDITION, CHANGE, DELETION
if not LogEntry._meta.installed:
    raise ImproperlyConfigured, "You'll need to put 'django.contrib.admin' in your INSTALLED_APPS setting before you can use the admin application."

if 'django.core.context_processors.auth' not in settings.TEMPLATE_CONTEXT_PROCESSORS:
    raise ImproperlyConfigured, "You'll need to put 'django.core.context_processors.auth' in your TEMPLATE_CONTEXT_PROCESSORS setting before you can use the admin application."

# The system will display a "Show all" link on the change list only if the
# total result count is less than or equal to this setting.
MAX_SHOW_ALL_ALLOWED = 200

# Changelist settings
ALL_VAR = 'all'
ORDER_VAR = 'o'
ORDER_TYPE_VAR = 'ot'
PAGE_VAR = 'p'
SEARCH_VAR = 'q'
IS_POPUP_VAR = 'pop'
ERROR_FLAG = 'e'

# Text to display within change-list table cells if the value is blank.
EMPTY_CHANGELIST_VALUE = '(None)'

use_raw_id_admin = lambda field: isinstance(field.rel, (models.ManyToOneRel, models.ManyToManyRel)) and field.rel.raw_id_admin

class IncorrectLookupParameters(Exception):
    pass

def quote(s):
    """
    Ensure that primary key values do not confuse the admin URLs by escaping
    any '/', '_' and ':' characters. Similar to urllib.quote, except that the
    quoting is slightly different so that it doesn't get automatically
    unquoted by the Web browser.
    """
    if type(s) != type(''):
        return s
    res = list(s)
    for i in range(len(res)):
        c = res[i]
        if c in ':/_':
            res[i] = '_%02X' % ord(c)
    return ''.join(res)

def unquote(s):
    """
    Undo the effects of quote(). Based heavily on urllib.unquote().
    """
    mychr = chr
    myatoi = int
    list = s.split('_')
    res = [list[0]]
    myappend = res.append
    del list[0]
    for item in list:
        if item[1:2]:
            try:
                myappend(mychr(myatoi(item[:2], 16)) + item[2:])
            except ValueError:
                myappend('_' + item)
        else:
            myappend('_' + item)
    return "".join(res)

def get_javascript_imports(opts, auto_populated_fields, field_sets):
# Put in any necessary JavaScript imports.
    js = ['js/core.js', 'js/admin/RelatedObjectLookups.js']
    if auto_populated_fields:
        js.append('js/urlify.js')
    if opts.has_field_type(models.DateTimeField) or opts.has_field_type(models.TimeField) or opts.has_field_type(models.DateField):
        js.extend(['js/calendar.js', 'js/admin/DateTimeShortcuts.js'])
    if opts.get_ordered_objects():
        js.extend(['js/getElementsBySelector.js', 'js/dom-drag.js' , 'js/admin/ordering.js'])
    if opts.admin.js:
        js.extend(opts.admin.js)
    seen_collapse = False
    for field_set in field_sets:
        if not seen_collapse and 'collapse' in field_set.classes:
            seen_collapse = True
            js.append('js/admin/CollapsedFieldsets.js')

        for field_line in field_set:
            try:
                for f in field_line:
                    if f.rel and isinstance(f, models.ManyToManyField) and f.rel.filter_interface:
                        js.extend(['js/SelectBox.js' , 'js/SelectFilter2.js'])
                        raise StopIteration
            except StopIteration:
                break
    return js

class AdminBoundField(object):
    def __init__(self, field, field_mapping, original):
        self.field = field
        self.original = original
        self.form_fields = [field_mapping[name] for name in self.field.get_manipulator_field_names('')]
        self.element_id = self.form_fields[0].get_id()
        self.has_label_first = not isinstance(self.field, models.BooleanField)
        self.raw_id_admin = use_raw_id_admin(field)
        self.is_date_time = isinstance(field, models.DateTimeField)
        self.is_file_field = isinstance(field, models.FileField)
        self.needs_add_label = field.rel and (isinstance(field.rel, models.ManyToOneRel) or isinstance(field.rel, models.ManyToManyRel)) and field.rel.to._meta.admin
        self.hidden = isinstance(self.field, models.AutoField)
        self.first = False

        classes = []
        if self.raw_id_admin:
            classes.append('nowrap')
        if max([bool(f.errors()) for f in self.form_fields]):
            classes.append('error')
        if classes:
            self.cell_class_attribute = u' class="%s" ' % ' '.join(classes)
        self._repr_filled = False

        if field.rel:
            self.related_url = mark_safe(u'../../../%s/%s/'
                    % (field.rel.to._meta.app_label,
                        field.rel.to._meta.object_name.lower()))

    def original_value(self):
        if self.original:
            return self.original.__dict__[self.field.attname]

    def existing_display(self):
        try:
            return self._display
        except AttributeError:
            if isinstance(self.field.rel, models.ManyToOneRel):
                self._display = force_unicode(getattr(self.original, self.field.name), strings_only=True)
            elif isinstance(self.field.rel, models.ManyToManyRel):
                self._display = u", ".join([force_unicode(obj) for obj in getattr(self.original, self.field.name).all()])
            return self._display

    def __repr__(self):
        return repr(self.__dict__)

    def html_error_list(self):
        return mark_safe(" ".join([form_field.html_error_list() for form_field in self.form_fields if form_field.errors]))

    def original_url(self):
        if self.is_file_field and self.original and self.field.attname:
            url_method = getattr(self.original, 'get_%s_url' % self.field.attname)
            if callable(url_method):
                return url_method()
        return ''

class AdminBoundFieldLine(object):
    def __init__(self, field_line, field_mapping, original):
        self.bound_fields = [field.bind(field_mapping, original, AdminBoundField) for field in field_line]
        for bound_field in self:
            bound_field.first = True
            break

    def __iter__(self):
        for bound_field in self.bound_fields:
            yield bound_field

    def __len__(self):
        return len(self.bound_fields)

class AdminBoundFieldSet(object):
    def __init__(self, field_set, field_mapping, original):
        self.name = field_set.name
        self.classes = field_set.classes
        self.description = field_set.description
        self.bound_field_lines = [field_line.bind(field_mapping, original, AdminBoundFieldLine) for field_line in field_set]

    def __iter__(self):
        for bound_field_line in self.bound_field_lines:
            yield bound_field_line

    def __len__(self):
        return len(self.bound_field_lines)

def render_change_form(model, manipulator, context, add=False, change=False, form_url=''):
    opts = model._meta
    app_label = opts.app_label
    auto_populated_fields = [f for f in opts.fields if f.prepopulate_from]
    field_sets = opts.admin.get_field_sets(opts)
    original = getattr(manipulator, 'original_object', None)
    bound_field_sets = [field_set.bind(context['form'], original, AdminBoundFieldSet) for field_set in field_sets]
    first_form_field_id = bound_field_sets[0].bound_field_lines[0].bound_fields[0].form_fields[0].get_id();
    ordered_objects = opts.get_ordered_objects()
    inline_related_objects = opts.get_followed_related_objects(manipulator.follow)
    extra_context = {
        'add': add,
        'change': change,
        'has_delete_permission': context['perms'][app_label][opts.get_delete_permission()],
        'has_change_permission': context['perms'][app_label][opts.get_change_permission()],
        'has_file_field': opts.has_field_type(models.FileField),
        'has_absolute_url': hasattr(model, 'get_absolute_url'),
        'auto_populated_fields': auto_populated_fields,
        'bound_field_sets': bound_field_sets,
        'first_form_field_id': first_form_field_id,
        'javascript_imports': get_javascript_imports(opts, auto_populated_fields, field_sets),
        'ordered_objects': ordered_objects,
        'inline_related_objects': inline_related_objects,
        'form_url': mark_safe(form_url),
        'opts': opts,
        'content_type_id': ContentType.objects.get_for_model(model).id,
    }
    context.update(extra_context)
    return render_to_response([
        "admin/%s/%s/change_form.html" % (app_label, opts.object_name.lower()),
        "admin/%s/change_form.html" % app_label,
        "admin/change_form.html"], context_instance=context)

def index(request):
    return render_to_response('admin/index.html', {'title': _('Site administration')}, context_instance=template.RequestContext(request))
index = staff_member_required(never_cache(index))

def add_stage(request, app_label, model_name, show_delete=False, form_url='', post_url=None, post_url_continue='../%s/', object_id_override=None):
    model = models.get_model(app_label, model_name)
    if model is None:
        raise Http404("App %r, model %r, not found" % (app_label, model_name))
    opts = model._meta

    if not request.user.has_perm(app_label + '.' + opts.get_add_permission()):
        raise PermissionDenied

    if post_url is None:
        if request.user.has_perm(app_label + '.' + opts.get_change_permission()):
            # redirect to list view
            post_url = '../'
        else:
            # Object list will give 'Permission Denied', so go back to admin home
            post_url = '../../../'

    manipulator = model.AddManipulator()
    if request.POST:
        new_data = request.POST.copy()

        if opts.has_field_type(models.FileField):
            new_data.update(request.FILES)

        errors = manipulator.get_validation_errors(new_data)
        manipulator.do_html2python(new_data)

        if not errors:
            new_object = manipulator.save(new_data)
            pk_value = new_object._get_pk_val()
            LogEntry.objects.log_action(request.user.id, ContentType.objects.get_for_model(model).id, pk_value, force_unicode(new_object), ADDITION)
            msg = _('The %(name)s "%(obj)s" was added successfully.') % {'name': force_unicode(opts.verbose_name), 'obj': force_unicode(new_object)}
            # Here, we distinguish between different save types by checking for
            # the presence of keys in request.POST.
            if "_continue" in request.POST:
                request.user.message_set.create(message=msg + ' ' + _("You may edit it again below."))
                if "_popup" in request.POST:
                    post_url_continue += "?_popup=1"
                return HttpResponseRedirect(post_url_continue % pk_value)
            if "_popup" in request.POST:
                return HttpResponse('<script type="text/javascript">opener.dismissAddAnotherPopup(window, "%s", "%s");</script>' % \
                    # escape() calls force_unicode.
                    (escape(pk_value), escape(new_object)))
            elif "_addanother" in request.POST:
                request.user.message_set.create(message=msg + ' ' + (_("You may add another %s below.") % force_unicode(opts.verbose_name)))
                return HttpResponseRedirect(request.path)
            else:
                request.user.message_set.create(message=msg)
                return HttpResponseRedirect(post_url)
    else:
        # Add default data.
        new_data = manipulator.flatten_data()

        # Override the defaults with GET params, if they exist.
        new_data.update(dict(request.GET.items()))

        errors = {}

    # Populate the FormWrapper.
    form = oldforms.FormWrapper(manipulator, new_data, errors)

    c = template.RequestContext(request, {
        'title': _('Add %s') % force_unicode(opts.verbose_name),
        'form': form,
        'is_popup': '_popup' in request.REQUEST,
        'show_delete': show_delete,
    })

    if object_id_override is not None:
        c['object_id'] = object_id_override

    return render_change_form(model, manipulator, c, add=True)
add_stage = staff_member_required(never_cache(add_stage))

def change_stage(request, app_label, model_name, object_id):
    model = models.get_model(app_label, model_name)
    object_id = unquote(object_id)
    if model is None:
        raise Http404("App %r, model %r, not found" % (app_label, model_name))
    opts = model._meta

    if not request.user.has_perm(app_label + '.' + opts.get_change_permission()):
        raise PermissionDenied

    if request.POST and "_saveasnew" in request.POST:
        return add_stage(request, app_label, model_name, form_url='../../add/')

    try:
        manipulator = model.ChangeManipulator(object_id)
    except model.DoesNotExist:
        raise Http404('%s object with primary key %r does not exist' % (model_name, escape(object_id)))

    if request.POST:
        new_data = request.POST.copy()

        if opts.has_field_type(models.FileField):
            new_data.update(request.FILES)

        errors = manipulator.get_validation_errors(new_data)
        manipulator.do_html2python(new_data)

        if not errors:
            new_object = manipulator.save(new_data)
            pk_value = new_object._get_pk_val()

            # Construct the change message.
            change_message = []
            if manipulator.fields_added:
                change_message.append(_('Added %s.') % get_text_list(manipulator.fields_added, _('and')))
            if manipulator.fields_changed:
                change_message.append(_('Changed %s.') % get_text_list(manipulator.fields_changed, _('and')))
            if manipulator.fields_deleted:
                change_message.append(_('Deleted %s.') % get_text_list(manipulator.fields_deleted, _('and')))
            change_message = ' '.join(change_message)
            if not change_message:
                change_message = _('No fields changed.')
            LogEntry.objects.log_action(request.user.id, ContentType.objects.get_for_model(model).id, pk_value, force_unicode(new_object), CHANGE, change_message)

            msg = _('The %(name)s "%(obj)s" was changed successfully.') % {'name': force_unicode(opts.verbose_name), 'obj': force_unicode(new_object)}
            if "_continue" in request.POST:
                request.user.message_set.create(message=msg + ' ' + _("You may edit it again below."))
                if '_popup' in request.REQUEST:
                    return HttpResponseRedirect(request.path + "?_popup=1")
                else:
                    return HttpResponseRedirect(request.path)
            elif "_saveasnew" in request.POST:
                request.user.message_set.create(message=_('The %(name)s "%(obj)s" was added successfully. You may edit it again below.') % {'name': force_unicode(opts.verbose_name), 'obj': force_unicode(new_object)})
                return HttpResponseRedirect("../%s/" % pk_value)
            elif "_addanother" in request.POST:
                request.user.message_set.create(message=msg + ' ' + (_("You may add another %s below.") % force_unicode(opts.verbose_name)))
                return HttpResponseRedirect("../add/")
            else:
                request.user.message_set.create(message=msg)
                return HttpResponseRedirect("../")
    else:
        # Populate new_data with a "flattened" version of the current data.
        new_data = manipulator.flatten_data()

        # TODO: do this in flatten_data...
        # If the object has ordered objects on its admin page, get the existing
        # order and flatten it into a comma-separated list of IDs.

        id_order_list = []
        for rel_obj in opts.get_ordered_objects():
            id_order_list.extend(getattr(manipulator.original_object, 'get_%s_order' % rel_obj.object_name.lower())())
        if id_order_list:
            new_data['order_'] = ','.join(map(str, id_order_list))
        errors = {}

    # Populate the FormWrapper.
    form = oldforms.FormWrapper(manipulator, new_data, errors)
    form.original = manipulator.original_object
    form.order_objects = []

    #TODO Should be done in flatten_data  / FormWrapper construction
    for related in opts.get_followed_related_objects():
        wrt = related.opts.order_with_respect_to
        if wrt and wrt.rel and wrt.rel.to == opts:
            func = getattr(manipulator.original_object, 'get_%s_list' %
                    related.get_accessor_name())
            orig_list = func()
            form.order_objects.extend(orig_list)

    c = template.RequestContext(request, {
        'title': _('Change %s') % force_unicode(opts.verbose_name),
        'form': form,
        'object_id': object_id,
        'original': manipulator.original_object,
        'is_popup': '_popup' in request.REQUEST,
    })
    return render_change_form(model, manipulator, c, change=True)
change_stage = staff_member_required(never_cache(change_stage))

def _nest_help(obj, depth, val):
    current = obj
    for i in range(depth):
        current = current[-1]
    current.append(val)

def _get_deleted_objects(deleted_objects, perms_needed, user, obj, opts, current_depth):
    "Helper function that recursively populates deleted_objects."
    nh = _nest_help # Bind to local variable for performance
    if current_depth > 16:
        return # Avoid recursing too deep.
    opts_seen = []
    for related in opts.get_all_related_objects():
        if related.opts in opts_seen:
            continue
        opts_seen.append(related.opts)
        rel_opts_name = related.get_accessor_name()
        if isinstance(related.field.rel, models.OneToOneRel):
            try:
                sub_obj = getattr(obj, rel_opts_name)
            except ObjectDoesNotExist:
                pass
            else:
                if related.opts.admin:
                    p = '%s.%s' % (related.opts.app_label, related.opts.get_delete_permission())
                    if not user.has_perm(p):
                        perms_needed.add(related.opts.verbose_name)
                        # We don't care about populating deleted_objects now.
                        continue
                if related.field.rel.edit_inline or not related.opts.admin:
                    # Don't display link to edit, because it either has no
                    # admin or is edited inline.
                    nh(deleted_objects, current_depth, [mark_safe(u'%s: %s' % (force_unicode(capfirst(related.opts.verbose_name)), sub_obj)), []])
                else:
                    # Display a link to the admin page.
                    nh(deleted_objects, current_depth, [mark_safe(u'%s: <a href="../../../../%s/%s/%s/">%s</a>' %
                        (escape(force_unicode(capfirst(related.opts.verbose_name))),
                            related.opts.app_label,
                            related.opts.object_name.lower(),
                            sub_obj._get_pk_val(), sub_obj)), []])
                _get_deleted_objects(deleted_objects, perms_needed, user, sub_obj, related.opts, current_depth+2)
        else:
            has_related_objs = False
            for sub_obj in getattr(obj, rel_opts_name).all():
                has_related_objs = True
                if related.field.rel.edit_inline or not related.opts.admin:
                    # Don't display link to edit, because it either has no
                    # admin or is edited inline.
                    nh(deleted_objects, current_depth, [u'%s: %s' % (force_unicode(capfirst(related.opts.verbose_name)), escape(sub_obj)), []])
                else:
                    # Display a link to the admin page.
                    nh(deleted_objects, current_depth, [mark_safe(u'%s: <a href="../../../../%s/%s/%s/">%s</a>' % \
                        (escape(force_unicode(capfirst(related.opts.verbose_name))), related.opts.app_label, related.opts.object_name.lower(), sub_obj._get_pk_val(), escape(sub_obj))), []])
                _get_deleted_objects(deleted_objects, perms_needed, user, sub_obj, related.opts, current_depth+2)
            # If there were related objects, and the user doesn't have
            # permission to delete them, add the missing perm to perms_needed.
            if related.opts.admin and has_related_objs:
                p = '%s.%s' % (related.opts.app_label, related.opts.get_delete_permission())
                if not user.has_perm(p):
                    perms_needed.add(related.opts.verbose_name)
    for related in opts.get_all_related_many_to_many_objects():
        if related.opts in opts_seen:
            continue
        opts_seen.append(related.opts)
        rel_opts_name = related.get_accessor_name()
        has_related_objs = False

        # related.get_accessor_name() could return None for symmetrical relationships
        if rel_opts_name:
            rel_objs = getattr(obj, rel_opts_name, None)
            if rel_objs:
                has_related_objs = True

        if has_related_objs:
            for sub_obj in rel_objs.all():
                if related.field.rel.edit_inline or not related.opts.admin:
                    # Don't display link to edit, because it either has no
                    # admin or is edited inline.
                    nh(deleted_objects, current_depth, [_('One or more %(fieldname)s in %(name)s: %(obj)s') % \
                        {'fieldname': force_unicode(related.field.verbose_name), 'name': force_unicode(related.opts.verbose_name), 'obj': escape(sub_obj)}, []])
                else:
                    # Display a link to the admin page.
                    nh(deleted_objects, current_depth, [
                        mark_safe((_('One or more %(fieldname)s in %(name)s:') % {'fieldname': escape(force_unicode(related.field.verbose_name)), 'name': escape(force_unicode(related.opts.verbose_name))}) + \
                        (u' <a href="../../../../%s/%s/%s/">%s</a>' % \
                            (related.opts.app_label, related.opts.module_name, sub_obj._get_pk_val(), escape(sub_obj)))), []])
        # If there were related objects, and the user doesn't have
        # permission to change them, add the missing perm to perms_needed.
        if related.opts.admin and has_related_objs:
            p = u'%s.%s' % (related.opts.app_label, related.opts.get_change_permission())
            if not user.has_perm(p):
                perms_needed.add(related.opts.verbose_name)

def delete_stage(request, app_label, model_name, object_id):
    model = models.get_model(app_label, model_name)
    object_id = unquote(object_id)
    if model is None:
        raise Http404("App %r, model %r, not found" % (app_label, model_name))
    opts = model._meta
    if not request.user.has_perm(app_label + '.' + opts.get_delete_permission()):
        raise PermissionDenied
    obj = get_object_or_404(model, pk=object_id)

    # Populate deleted_objects, a data structure of all related objects that
    # will also be deleted.
    deleted_objects = [mark_safe(u'%s: <a href="../../%s/">%s</a>' % (escape(force_unicode(capfirst(opts.verbose_name))), force_unicode(object_id), escape(obj))), []]
    perms_needed = set()
    _get_deleted_objects(deleted_objects, perms_needed, request.user, obj, opts, 1)

    if request.POST: # The user has already confirmed the deletion.
        if perms_needed:
            raise PermissionDenied
        obj_display = force_unicode(obj)
        obj.delete()
        LogEntry.objects.log_action(request.user.id, ContentType.objects.get_for_model(model).id, object_id, obj_display, DELETION)
        request.user.message_set.create(message=_('The %(name)s "%(obj)s" was deleted successfully.') % {'name': force_unicode(opts.verbose_name), 'obj': obj_display})
        return HttpResponseRedirect("../../")
    extra_context = {
        "title": _("Are you sure?"),
        "object_name": force_unicode(opts.verbose_name),
        "object": obj,
        "deleted_objects": deleted_objects,
        "perms_lacking": perms_needed,
        "opts": model._meta,
    }
    return render_to_response(["admin/%s/%s/delete_confirmation.html" % (app_label, opts.object_name.lower() ),
                               "admin/%s/delete_confirmation.html" % app_label ,
                               "admin/delete_confirmation.html"], extra_context, context_instance=template.RequestContext(request))
delete_stage = staff_member_required(never_cache(delete_stage))

def history(request, app_label, model_name, object_id):
    model = models.get_model(app_label, model_name)
    object_id = unquote(object_id)
    if model is None:
        raise Http404("App %r, model %r, not found" % (app_label, model_name))
    action_list = LogEntry.objects.filter(object_id=object_id,
        content_type__id__exact=ContentType.objects.get_for_model(model).id).select_related().order_by('action_time')
    # If no history was found, see whether this object even exists.
    obj = get_object_or_404(model, pk=object_id)
    extra_context = {
        'title': _('Change history: %s') % obj,
        'action_list': action_list,
        'module_name': force_unicode(capfirst(model._meta.verbose_name_plural)),
        'object': obj,
    }
    return render_to_response(["admin/%s/%s/object_history.html" % (app_label, model._meta.object_name.lower()),
                               "admin/%s/object_history.html" % app_label ,
                               "admin/object_history.html"], extra_context, context_instance=template.RequestContext(request))
history = staff_member_required(never_cache(history))

class ChangeList(object):
    def __init__(self, request, model):
        self.model = model
        self.opts = model._meta
        self.lookup_opts = self.opts
        self.manager = self.opts.admin.manager

        # Get search parameters from the query string.
        try:
            self.page_num = int(request.GET.get(PAGE_VAR, 0))
        except ValueError:
            self.page_num = 0
        self.show_all = ALL_VAR in request.GET
        self.is_popup = IS_POPUP_VAR in request.GET
        self.params = dict(request.GET.items())
        if PAGE_VAR in self.params:
            del self.params[PAGE_VAR]
        if ERROR_FLAG in self.params:
            del self.params[ERROR_FLAG]

        self.order_field, self.order_type = self.get_ordering()
        self.query = request.GET.get(SEARCH_VAR, '')
        self.query_set = self.get_query_set()
        self.get_results(request)
        self.title = (self.is_popup and _('Select %s') % force_unicode(self.opts.verbose_name) or _('Select %s to change') % force_unicode(self.opts.verbose_name))
        self.filter_specs, self.has_filters = self.get_filters(request)
        self.pk_attname = self.lookup_opts.pk.attname

    def get_filters(self, request):
        filter_specs = []
        if self.lookup_opts.admin.list_filter and not self.opts.one_to_one_field:
            filter_fields = [self.lookup_opts.get_field(field_name) \
                              for field_name in self.lookup_opts.admin.list_filter]
            for f in filter_fields:
                spec = FilterSpec.create(f, request, self.params, self.model)
                if spec and spec.has_output():
                    filter_specs.append(spec)
        return filter_specs, bool(filter_specs)

    def get_query_string(self, new_params=None, remove=None):
        if new_params is None: new_params = {}
        if remove is None: remove = []
        p = self.params.copy()
        for r in remove:
            for k in p.keys():
                if k.startswith(r):
                    del p[k]
        for k, v in new_params.items():
            if k in p and v is None:
                del p[k]
            elif v is not None:
                p[k] = v
        return mark_safe('?' + '&amp;'.join([u'%s=%s' % (k, v) for k, v in p.items()]).replace(' ', '%20'))

    def get_results(self, request):
        paginator = QuerySetPaginator(self.query_set, self.lookup_opts.admin.list_per_page)

        # Get the number of objects, with admin filters applied.
        try:
            result_count = paginator.count
        # Naked except! Because we don't have any other way of validating
        # "params". They might be invalid if the keyword arguments are
        # incorrect, or if the values are not in the correct type (which would
        # result in a database error).
        except:
            raise IncorrectLookupParameters

        # Get the total number of objects, with no admin filters applied.
        # Perform a slight optimization: Check to see whether any filters were
        # given. If not, use paginator.hits to calculate the number of objects,
        # because we've already done paginator.hits and the value is cached.
        if not self.query_set.query.where:
            full_result_count = result_count
        else:
            full_result_count = self.manager.count()

        can_show_all = result_count <= MAX_SHOW_ALL_ALLOWED
        multi_page = result_count > self.lookup_opts.admin.list_per_page

        # Get the list of objects to display on this page.
        if (self.show_all and can_show_all) or not multi_page:
            result_list = list(self.query_set)
        else:
            try:
                result_list = paginator.page(self.page_num+1).object_list
            except InvalidPage:
                result_list = ()

        self.result_count = result_count
        self.full_result_count = full_result_count
        self.result_list = result_list
        self.can_show_all = can_show_all
        self.multi_page = multi_page
        self.paginator = paginator

    def get_ordering(self):
        lookup_opts, params = self.lookup_opts, self.params
        # For ordering, first check the "ordering" parameter in the admin
        # options, then check the object's default ordering. If neither of
        # those exist, order descending by ID by default. Finally, look for
        # manually-specified ordering from the query string.
        ordering = lookup_opts.admin.ordering or lookup_opts.ordering or ['-' + lookup_opts.pk.name]

        if ordering[0].startswith('-'):
            order_field, order_type = ordering[0][1:], 'desc'
        else:
            order_field, order_type = ordering[0], 'asc'
        if ORDER_VAR in params:
            try:
                field_name = lookup_opts.admin.list_display[int(params[ORDER_VAR])]
                try:
                    f = lookup_opts.get_field(field_name)
                except models.FieldDoesNotExist:
                    # see if field_name is a name of a non-field
                    # that allows sorting
                    try:
                        attr = getattr(lookup_opts.admin.manager.model, field_name)
                        order_field = attr.admin_order_field
                    except AttributeError:
                        pass
                else:
                    if not isinstance(f.rel, models.ManyToOneRel) or not f.null:
                        order_field = f.name
            except (IndexError, ValueError):
                pass # Invalid ordering specified. Just use the default.
        if ORDER_TYPE_VAR in params and params[ORDER_TYPE_VAR] in ('asc', 'desc'):
            order_type = params[ORDER_TYPE_VAR]
        return order_field, order_type

    def get_query_set(self):
        qs = self.manager.get_query_set()
        lookup_params = self.params.copy() # a dictionary of the query string
        for i in (ALL_VAR, ORDER_VAR, ORDER_TYPE_VAR, SEARCH_VAR, IS_POPUP_VAR):
            if i in lookup_params:
                del lookup_params[i]
        for key, value in lookup_params.items():
            if not isinstance(key, str):
                # 'key' will be used as a keyword argument later, so Python
                # requires it to be a string.
                del lookup_params[key]
                lookup_params[smart_str(key)] = value

        # Apply lookup parameters from the query string.
        qs = qs.filter(**lookup_params)

        # Use select_related() if one of the list_display options is a field
        # with a relationship.
        if self.lookup_opts.admin.list_select_related:
            qs = qs.select_related()
        else:
            for field_name in self.lookup_opts.admin.list_display:
                try:
                    f = self.lookup_opts.get_field(field_name)
                except models.FieldDoesNotExist:
                    pass
                else:
                    if isinstance(f.rel, models.ManyToOneRel):
                        qs = qs.select_related()
                        break

        # Set ordering.
        if self.order_field:
            qs = qs.order_by('%s%s' % ((self.order_type == 'desc' and '-' or ''), self.order_field))

        # Apply keyword searches.
        def construct_search(field_name):
            if field_name.startswith('^'):
                return "%s__istartswith" % field_name[1:]
            elif field_name.startswith('='):
                return "%s__iexact" % field_name[1:]
            elif field_name.startswith('@'):
                return "%s__search" % field_name[1:]
            else:
                return "%s__icontains" % field_name

        if self.lookup_opts.admin.search_fields and self.query:
            for bit in self.query.split():
                or_queries = [models.Q(**{construct_search(field_name): bit}) for field_name in self.lookup_opts.admin.search_fields]
                other_qs = QuerySet(self.model)
                other_qs.dup_select_related(qs)
                other_qs = other_qs.filter(reduce(operator.or_, or_queries))
                qs = qs & other_qs

        if self.opts.one_to_one_field:
            qs = qs.complex_filter(self.opts.one_to_one_field.rel.limit_choices_to)

        return qs

    def url_for_result(self, result):
        return "%s/" % quote(getattr(result, self.pk_attname))

def change_list(request, app_label, model_name):
    model = models.get_model(app_label, model_name)
    if model is None:
        raise Http404("App %r, model %r, not found" % (app_label, model_name))
    if not request.user.has_perm(app_label + '.' + model._meta.get_change_permission()):
        raise PermissionDenied
    try:
        cl = ChangeList(request, model)
    except IncorrectLookupParameters:
        # Wacky lookup parameters were given, so redirect to the main
        # changelist page, without parameters, and pass an 'invalid=1'
        # parameter via the query string. If wacky parameters were given and
        # the 'invalid=1' parameter was already in the query string, something
        # is screwed up with the database, so display an error page.
        if ERROR_FLAG in request.GET.keys():
            return render_to_response('admin/invalid_setup.html', {'title': _('Database error')})
        return HttpResponseRedirect(request.path + '?' + ERROR_FLAG + '=1')
    c = template.RequestContext(request, {
        'title': cl.title,
        'is_popup': cl.is_popup,
        'cl': cl,
    })
    c.update({'has_add_permission': c['perms'][app_label][cl.opts.get_add_permission()]}),
    return render_to_response(['admin/%s/%s/change_list.html' % (app_label, cl.opts.object_name.lower()),
                               'admin/%s/change_list.html' % app_label,
                               'admin/change_list.html'], context_instance=c)
change_list = staff_member_required(never_cache(change_list))
