from django.contrib.admin.filterspecs import FilterSpec
from django.contrib.admin.options import IncorrectLookupParameters
from django.contrib.admin.util import quote
from django.core.exceptions import SuspiciousOperation
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:
                raise IncorrectLookupParameters

        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(',')

            # if key ends with __isnull, special case '' and false
            if key.endswith('__isnull'):
                if value.lower() in ('', 'false'):
                    lookup_params[key] = False
                else:
                    lookup_params[key] = True

            if not self.model_admin.lookup_allowed(key):
                raise SuspiciousOperation(
                    "Filtering by %s not allowed" % key
                )

        # 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))
