from django.contrib.admin.filterspecs import FilterSpec

from django.contrib.admin.options import IncorrectLookupParameters

from django.contrib.admin.util import quote

from django.core.paginator import Paginator, InvalidPage

from django.db import models

from django.db.models.query import QuerySet

from django.utils.encoding import force_unicode, smart_str

from django.utils.translation import ugettext

from django.utils.http import urlencode

import operator

# 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'

TO_FIELD_VAR = 't'

IS_POPUP_VAR = 'pop'

ERROR_FLAG = 'e'

# Text to display within change-list table cells if the value is blank.

EMPTY_CHANGELIST_VALUE = '(None)'

class ChangeList(object):

    def __init__(self, request, model, list_display, list_display_links, list_filter, date_hierarchy, search_fields, list_select_related, list_per_page, list_editable, model_admin):

        self.model = model

        self.opts = model._meta

        self.lookup_opts = self.opts

        self.root_query_set = model_admin.queryset(request)

        self.list_display = list_display

        self.list_display_links = list_display_links

        self.list_filter = list_filter

        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_editable = list_editable

        self.model_admin = model_admin

        # 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.to_field = request.GET.get(TO_FIELD_VAR)

        self.params = dict(request.GET.items())

        if PAGE_VAR in self.params:

            del self.params[PAGE_VAR]

        if TO_FIELD_VAR in self.params:

            del self.params[TO_FIELD_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 ugettext('Select %s') % force_unicode(self.opts.verbose_name) or ugettext('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.list_filter:

            filter_fields = [self.lookup_opts.get_field(field_name) for field_name in self.list_filter]

            for f in filter_fields:

                spec = FilterSpec.create(f, request, self.params, self.model, self.model_admin)

                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 v is None:

                if k in p:

                    del p[k]

            else:

                p[k] = v

        return '?%s' % urlencode(p)

    def get_results(self, request):

        paginator = Paginator(self.query_set, 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.

        # 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.root_query_set.count()

        can_show_all = result_count <= MAX_SHOW_ALL_ALLOWED

        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.query_set._clone()

        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 = self.model_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 = self.list_display[int(params[ORDER_VAR])]

                try:

                    f = lookup_opts.get_field(field_name)

                except models.FieldDoesNotExist:

                    # See whether field_name is a name of a non-field

                    # that allows sorting.

                    try:

                        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)

                        order_field = attr.admin_order_field

                    except AttributeError:

                        pass

                else:

                    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.root_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

            # if key ends with __in, split parameter into separate values

            if key.endswith('__in'):

                lookup_params[key] = value.split(',')

        # Apply lookup parameters from the query string.

        try:

            qs = qs.filter(**lookup_params)

        # 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, so we might get FieldError, ValueError,

        # ValicationError, or ? from a custom field that raises yet something else 

        # when handed impossible data.

        except:

            raise IncorrectLookupParameters

        # Use select_related() if one of the list_display options is a field

        # with a relationship and the provided queryset doesn't already have

        # select_related defined.

        if not qs.query.select_related:

            if self.list_select_related:

                qs = qs.select_related()

            else:

                for field_name in self.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.search_fields and self.query:

            for bit in self.query.split():

                or_queries = [models.Q(**{construct_search(str(field_name)): bit}) for field_name in self.search_fields]

                qs = qs.filter(reduce(operator.or_, or_queries))

            for field_name in self.search_fields:

                if '__' in field_name:

                    qs = qs.distinct()

                    break

        return qs

    def url_for_result(self, result):

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