main.py

import warnings
from datetime import datetime, timedelta

from django import forms
from django.conf import settings
from django.contrib import messages
from django.contrib.admin import FieldListFilter
from django.contrib.admin.exceptions import (
    DisallowedModelAdminLookup,
    DisallowedModelAdminToField,
)
from django.contrib.admin.options import (
    IS_FACETS_VAR,
    IS_POPUP_VAR,
    TO_FIELD_VAR,
    IncorrectLookupParameters,
    ShowFacets,
)
from django.contrib.admin.utils import (
    build_q_object_from_lookup_parameters,
    get_fields_from_path,
    lookup_spawns_duplicates,
    prepare_lookup_value,
    quote,
)
from django.core.exceptions import (
    FieldDoesNotExist,
    ImproperlyConfigured,
    SuspiciousOperation,
)
from django.core.paginator import InvalidPage
from django.db.models import Exists, F, Field, ManyToOneRel, OrderBy, OuterRef
from django.db.models.expressions import Combinable
from django.urls import reverse
from django.utils.deprecation import RemovedInDjango60Warning
from django.utils.http import urlencode
from django.utils.inspect import func_supports_parameter
from django.utils.timezone import make_aware
from django.utils.translation import gettext

# Changelist settings
ALL_VAR = "all"
ORDER_VAR = "o"
PAGE_VAR = "p"
SEARCH_VAR = "q"
ERROR_FLAG = "e"

IGNORED_PARAMS = (
    ALL_VAR,
    ORDER_VAR,
    SEARCH_VAR,
    IS_FACETS_VAR,
    IS_POPUP_VAR,
    TO_FIELD_VAR,
)


class ChangeListSearchForm(forms.Form):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # Populate "fields" dynamically because SEARCH_VAR is a variable:
        self.fields = {
            SEARCH_VAR: forms.CharField(required=False, strip=False),
        }


class ChangeList:
    search_form_class = ChangeListSearchForm

    def __init__(
        self,
        request,
        model,
        list_display,
        list_display_links,
        list_filter,
        date_hierarchy,
        search_fields,
        list_select_related,
        list_per_page,
        list_max_show_all,
        list_editable,
        model_admin,
        sortable_by,
        search_help_text,
    ):
        self.model = model
        self.opts = model._meta
        self.lookup_opts = self.opts
        self.root_queryset = model_admin.get_queryset(request)
        self.list_display = list_display
        self.list_display_links = list_display_links
        self.list_filter = list_filter
        self.has_filters = None
        self.has_active_filters = None
        self.clear_all_filters_qs = None
        self.date_hierarchy = date_hierarchy
        self.search_fields = search_fields
        self.list_select_related = list_select_related
        self.list_per_page = list_per_page
        self.list_max_show_all = list_max_show_all
        self.model_admin = model_admin
        self.preserved_filters = model_admin.get_preserved_filters(request)
        self.sortable_by = sortable_by
        self.search_help_text = search_help_text

        # Get search parameters from the query string.
        _search_form = self.search_form_class(request.GET)
        if not _search_form.is_valid():
            for error in _search_form.errors.values():
                messages.error(request, ", ".join(error))
        self.query = _search_form.cleaned_data.get(SEARCH_VAR) or ""
        try:
            self.page_num = int(request.GET.get(PAGE_VAR, 1))
        except ValueError:
            self.page_num = 1
        self.show_all = ALL_VAR in request.GET
        self.is_popup = IS_POPUP_VAR in request.GET
        self.add_facets = model_admin.show_facets is ShowFacets.ALWAYS or (
            model_admin.show_facets is ShowFacets.ALLOW and IS_FACETS_VAR in request.GET
        )
        self.is_facets_optional = model_admin.show_facets is ShowFacets.ALLOW
        to_field = request.GET.get(TO_FIELD_VAR)
        if to_field and not model_admin.to_field_allowed(request, to_field):
            raise DisallowedModelAdminToField(
                "The field %s cannot be referenced." % to_field
            )
        self.to_field = to_field
        self.params = dict(request.GET.items())
        self.filter_params = dict(request.GET.lists())
        if PAGE_VAR in self.params:
            del self.params[PAGE_VAR]
            del self.filter_params[PAGE_VAR]
        if ERROR_FLAG in self.params:
            del self.params[ERROR_FLAG]
            del self.filter_params[ERROR_FLAG]
        self.remove_facet_link = self.get_query_string(remove=[IS_FACETS_VAR])
        self.add_facet_link = self.get_query_string({IS_FACETS_VAR: True})

        if self.is_popup:
            self.list_editable = ()
        else:
            self.list_editable = list_editable
        self.queryset = self.get_queryset(request)
        self.get_results(request)
        if self.is_popup:
            title = gettext("Select %s")
        elif self.model_admin.has_change_permission(request):
            title = gettext("Select %s to change")
        else:
            title = gettext("Select %s to view")
        self.title = title % self.opts.verbose_name
        self.pk_attname = self.lookup_opts.pk.attname

    def __repr__(self):
        return "<%s: model=%s model_admin=%s>" % (
            self.__class__.__qualname__,
            self.model.__qualname__,
            self.model_admin.__class__.__qualname__,
        )

    def get_filters_params(self, params=None):
        """
        Return all params except IGNORED_PARAMS.
        """
        params = params or self.filter_params
        lookup_params = params.copy()  # a dictionary of the query string
        # Remove all the parameters that are globally and systematically
        # ignored.
        for ignored in IGNORED_PARAMS:
            if ignored in lookup_params:
                del lookup_params[ignored]
        return lookup_params

    def get_filters(self, request):
        lookup_params = self.get_filters_params()
        may_have_duplicates = False
        has_active_filters = False

        supports_request = func_supports_parameter(
            self.model_admin.lookup_allowed, "request"
        )
        if not supports_request:
            warnings.warn(
                f"`request` must be added to the signature of "
                f"{self.model_admin.__class__.__qualname__}.lookup_allowed().",
                RemovedInDjango60Warning,
            )
        for key, value_list in lookup_params.items():
            for value in value_list:
                params = (key, value, request) if supports_request else (key, value)
                if not self.model_admin.lookup_allowed(*params):
                    raise DisallowedModelAdminLookup(f"Filtering by {key} not allowed")

        filter_specs = []
        for list_filter in self.list_filter:
            lookup_params_count = len(lookup_params)
            if callable(list_filter):
                # This is simply a custom list filter class.
                spec = list_filter(request, lookup_params, self.model, self.model_admin)
            else:
                field_path = None
                if isinstance(list_filter, (tuple, list)):
                    # This is a custom FieldListFilter class for a given field.
                    field, field_list_filter_class = list_filter
                else:
                    # This is simply a field name, so use the default
                    # FieldListFilter class that has been registered for the
                    # type of the given field.
                    field, field_list_filter_class = list_filter, FieldListFilter.create
                if not isinstance(field, Field):
                    field_path = field
                    field = get_fields_from_path(self.model, field_path)[-1]

                spec = field_list_filter_class(
                    field,
                    request,
                    lookup_params,
                    self.model,
                    self.model_admin,
                    field_path=field_path,
                )
                # field_list_filter_class removes any lookup_params it
                # processes. If that happened, check if duplicates should be
                # removed.
                if lookup_params_count > len(lookup_params):
                    may_have_duplicates |= lookup_spawns_duplicates(
                        self.lookup_opts,
                        field_path,
                    )
            if spec and spec.has_output():
                filter_specs.append(spec)
                if lookup_params_count > len(lookup_params):
                    has_active_filters = True

        if self.date_hierarchy:
            # Create bounded lookup parameters so that the query is more
            # efficient.
            year = lookup_params.pop("%s__year" % self.date_hierarchy, None)
            if year is not None:
                month = lookup_params.pop("%s__month" % self.date_hierarchy, None)
                day = lookup_params.pop("%s__day" % self.date_hierarchy, None)
                try:
                    from_date = datetime(
                        int(year[-1]),
                        int(month[-1] if month is not None else 1),
                        int(day[-1] if day is not None else 1),
                    )
                except ValueError as e:
                    raise IncorrectLookupParameters(e) from e
                if day:
                    to_date = from_date + timedelta(days=1)
                elif month:
                    # In this branch, from_date will always be the first of a
                    # month, so advancing 32 days gives the next month.
                    to_date = (from_date + timedelta(days=32)).replace(day=1)
                else:
                    to_date = from_date.replace(year=from_date.year + 1)
                if settings.USE_TZ:
                    from_date = make_aware(from_date)
                    to_date = make_aware(to_date)
                lookup_params.update(
                    {
                        "%s__gte" % self.date_hierarchy: [from_date],
                        "%s__lt" % self.date_hierarchy: [to_date],
                    }
                )

        # At this point, all the parameters used by the various ListFilters
        # have been removed from lookup_params, which now only contains other
        # parameters passed via the query string. We now loop through the
        # remaining parameters both to ensure that all the parameters are valid
        # fields and to determine if at least one of them spawns duplicates. If
        # the lookup parameters aren't real fields, then bail out.
        try:
            for key, value in lookup_params.items():
                lookup_params[key] = prepare_lookup_value(key, value)
                may_have_duplicates |= lookup_spawns_duplicates(self.lookup_opts, key)
            return (
                filter_specs,
                bool(filter_specs),
                lookup_params,
                may_have_duplicates,
                has_active_filters,
            )
        except FieldDoesNotExist as e:
            raise IncorrectLookupParameters(e) from e

    def get_query_string(self, new_params=None, remove=None):
        if new_params is None:
            new_params = {}
        if remove is None:
            remove = []
        p = self.filter_params.copy()
        for r in remove:
            for k in list(p):
                if k.startswith(r):
                    del p[k]
        for k, v in new_params.items():
            if v is None:
                if k in p:
                    del p[k]
            else:
                p[k] = v
        return "?%s" % urlencode(sorted(p.items()), doseq=True)

    def get_results(self, request):
        paginator = self.model_admin.get_paginator(
            request, self.queryset, self.list_per_page
        )
        # Get the number of objects, with admin filters applied.
        result_count = paginator.count

        # Get the total number of objects, with no admin filters applied.
        # Note this isn't necessarily the same as result_count in the case of
        # no filtering. Filters defined in list_filters may still apply some
        # default filtering which may be removed with query parameters.
        if self.model_admin.show_full_result_count:
            full_result_count = self.root_queryset.count()
        else:
            full_result_count = None
        can_show_all = result_count <= self.list_max_show_all
        multi_page = result_count > self.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 = self.queryset._clone()
        else:
            try:
                result_list = paginator.page(self.page_num).object_list
            except InvalidPage:
                raise IncorrectLookupParameters

        self.result_count = result_count
        self.show_full_result_count = self.model_admin.show_full_result_count
        # Admin actions are shown if there is at least one entry
        # or if entries are not counted because show_full_result_count is disabled
        self.show_admin_actions = not self.show_full_result_count or bool(
            full_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_default_ordering(self):
        ordering = []
        if self.model_admin.ordering:
            ordering = self.model_admin.ordering
        elif self.lookup_opts.ordering:
            ordering = self.lookup_opts.ordering
        return ordering

    def get_ordering_field(self, field_name):
        """
        Return the proper model field name corresponding to the given
        field_name to use for ordering. field_name may either be the name of a
        proper model field or the name of a method (on the admin or model) or a
        callable with the 'admin_order_field' attribute. Return None if no
        proper model field name can be matched.
        """
        try:
            field = self.lookup_opts.get_field(field_name)
            return field.name
        except FieldDoesNotExist:
            # See whether field_name is a name of a non-field
            # that allows sorting.
            if callable(field_name):
                attr = field_name
            elif hasattr(self.model_admin, field_name):
                attr = getattr(self.model_admin, field_name)
            else:
                attr = getattr(self.model, field_name)
            if isinstance(attr, property) and hasattr(attr, "fget"):
                attr = attr.fget
            return getattr(attr, "admin_order_field", None)

    def get_ordering(self, request, queryset):
        """
        Return the list of ordering fields for the change list.
        First check the get_ordering() method in model admin, then check
        the object's default ordering. Then, any manually-specified ordering
        from the query string overrides anything. Finally, a deterministic
        order is guaranteed by calling _get_deterministic_ordering() with the
        constructed ordering.
        """
        params = self.params
        ordering = list(
            self.model_admin.get_ordering(request) or self._get_default_ordering()
        )
        if ORDER_VAR in params:
            # Clear ordering and used params
            ordering = []
            order_params = params[ORDER_VAR].split(".")
            for p in order_params:
                try:
                    none, pfx, idx = p.rpartition("-")
                    field_name = self.list_display[int(idx)]
                    order_field = self.get_ordering_field(field_name)
                    if not order_field:
                        continue  # No 'admin_order_field', skip it
                    if isinstance(order_field, OrderBy):
                        if pfx == "-":
                            order_field = order_field.copy()
                            order_field.reverse_ordering()
                        ordering.append(order_field)
                    elif hasattr(order_field, "resolve_expression"):
                        # order_field is an expression.
                        ordering.append(
                            order_field.desc() if pfx == "-" else order_field.asc()
                        )
                    # reverse order if order_field has already "-" as prefix
                    elif pfx == "-" and order_field.startswith(pfx):
                        ordering.append(order_field.removeprefix(pfx))
                    else:
                        ordering.append(pfx + order_field)
                except (IndexError, ValueError):
                    continue  # Invalid ordering specified, skip it.

        # Add the given query's ordering fields, if any.
        ordering.extend(queryset.query.order_by)

        return self._get_deterministic_ordering(ordering)

    def _get_deterministic_ordering(self, ordering):
        """
        Ensure a deterministic order across all database backends. Search for a
        single field or unique together set of fields providing a total
        ordering. If these are missing, augment the ordering with a descendant
        primary key.
        """
        ordering = list(ordering)
        ordering_fields = set()
        total_ordering_fields = {"pk"} | {
            field.attname
            for field in self.lookup_opts.fields
            if field.unique and not field.null
        }
        for part in ordering:
            # Search for single field providing a total ordering.
            field_name = None
            if isinstance(part, str):
                field_name = part.lstrip("-")
            elif isinstance(part, F):
                field_name = part.name
            elif isinstance(part, OrderBy) and isinstance(part.expression, F):
                field_name = part.expression.name
            if field_name:
                # Normalize attname references by using get_field().
                try:
                    field = self.lookup_opts.get_field(field_name)
                except FieldDoesNotExist:
                    # Could be "?" for random ordering or a related field
                    # lookup. Skip this part of introspection for now.
                    continue
                # Ordering by a related field name orders by the referenced
                # model's ordering. Skip this part of introspection for now.
                if field.remote_field and field_name == field.name:
                    continue
                if field.attname in total_ordering_fields:
                    break
                ordering_fields.add(field.attname)
        else:
            # No single total ordering field, try unique_together and total
            # unique constraints.
            constraint_field_names = (
                *self.lookup_opts.unique_together,
                *(
                    constraint.fields
                    for constraint in self.lookup_opts.total_unique_constraints
                ),
            )
            for field_names in constraint_field_names:
                # Normalize attname references by using get_field().
                fields = [
                    self.lookup_opts.get_field(field_name) for field_name in field_names
                ]
                # Composite unique constraints containing a nullable column
                # cannot ensure total ordering.
                if any(field.null for field in fields):
                    continue
                if ordering_fields.issuperset(field.attname for field in fields):
                    break
            else:
                # If no set of unique fields is present in the ordering, rely
                # on the primary key to provide total ordering.
                ordering.append("-pk")
        return ordering

    def get_ordering_field_columns(self):
        """
        Return a dictionary of ordering field column numbers and asc/desc.
        """
        # We must cope with more than one column having the same underlying sort
        # field, so we base things on column numbers.
        ordering = self._get_default_ordering()
        ordering_fields = {}
        if ORDER_VAR not in self.params:
            # for ordering specified on ModelAdmin or model Meta, we don't know
            # the right column numbers absolutely, because there might be more
            # than one column associated with that ordering, so we guess.
            for field in ordering:
                if isinstance(field, (Combinable, OrderBy)):
                    if not isinstance(field, OrderBy):
                        field = field.asc()
                    if isinstance(field.expression, F):
                        order_type = "desc" if field.descending else "asc"
                        field = field.expression.name
                    else:
                        continue
                elif field.startswith("-"):
                    field = field.removeprefix("-")
                    order_type = "desc"
                else:
                    order_type = "asc"
                for index, attr in enumerate(self.list_display):
                    if self.get_ordering_field(attr) == field:
                        ordering_fields[index] = order_type
                        break
        else:
            for p in self.params[ORDER_VAR].split("."):
                none, pfx, idx = p.rpartition("-")
                try:
                    idx = int(idx)
                except ValueError:
                    continue  # skip it
                ordering_fields[idx] = "desc" if pfx == "-" else "asc"
        return ordering_fields

    def get_queryset(self, request, exclude_parameters=None):
        # First, we collect all the declared list filters.
        (
            self.filter_specs,
            self.has_filters,
            remaining_lookup_params,
            filters_may_have_duplicates,
            self.has_active_filters,
        ) = self.get_filters(request)
        # Then, we let every list filter modify the queryset to its liking.
        qs = self.root_queryset
        for filter_spec in self.filter_specs:
            if (
                exclude_parameters is None
                or filter_spec.expected_parameters() != exclude_parameters
            ):
                new_qs = filter_spec.queryset(request, qs)
                if new_qs is not None:
                    qs = new_qs

        try:
            # Finally, we apply the remaining lookup parameters from the query
            # string (i.e. those that haven't already been processed by the
            # filters).
            q_object = build_q_object_from_lookup_parameters(remaining_lookup_params)
            qs = qs.filter(q_object)
        except (SuspiciousOperation, ImproperlyConfigured):
            # Allow certain types of errors to be re-raised as-is so that the
            # caller can treat them in a special way.
            raise
        except Exception as e:
            # Every other error is caught with a naked except, because we don't
            # have any other way of validating lookup parameters. They might be
            # invalid if the keyword arguments are incorrect, or if the values
            # are not in the correct type, so we might get FieldError,
            # ValueError, ValidationError, or ?.
            raise IncorrectLookupParameters(e)

        # Apply search results
        qs, search_may_have_duplicates = self.model_admin.get_search_results(
            request,
            qs,
            self.query,
        )

        # Set query string for clearing all filters.
        self.clear_all_filters_qs = self.get_query_string(
            new_params=remaining_lookup_params,
            remove=self.get_filters_params(),
        )
        # Remove duplicates from results, if necessary
        if filters_may_have_duplicates | search_may_have_duplicates:
            qs = qs.filter(pk=OuterRef("pk"))
            qs = self.root_queryset.filter(Exists(qs))

        # Set ordering.
        ordering = self.get_ordering(request, qs)
        qs = qs.order_by(*ordering)

        if not qs.query.select_related:
            qs = self.apply_select_related(qs)

        return qs

    def apply_select_related(self, qs):
        if self.list_select_related is True:
            return qs.select_related()

        if self.list_select_related is False:
            if self.has_related_field_in_list_display():
                return qs.select_related()

        if self.list_select_related:
            return qs.select_related(*self.list_select_related)
        return qs

    def has_related_field_in_list_display(self):
        for field_name in self.list_display:
            try:
                field = self.lookup_opts.get_field(field_name)
            except FieldDoesNotExist:
                pass
            else:
                if isinstance(field.remote_field, ManyToOneRel):
                    # <FK>_id field names don't require a join.
                    if field_name != field.get_attname():
                        return True
        return False

    def url_for_result(self, result):
        pk = getattr(result, self.pk_attname)
        return reverse(
            "admin:%s_%s_change" % (self.opts.app_label, self.opts.model_name),
            args=(quote(pk),),
            current_app=self.model_admin.admin_site.name,
        )