"""
This encapsulates the logic for displaying filters in the Django admin.
Filters are specified in models with the "list_filter" option.

Each filter subclass knows how to display a filter for a field that passes a
certain test -- e.g. being a DateField or ForeignKey.
"""
import datetime

from django.contrib.admin.options import IncorrectLookupParameters
from django.contrib.admin.utils import (
    get_model_from_relation, prepare_lookup_value, reverse_field_path,
)
from django.core.exceptions import ImproperlyConfigured, ValidationError
from django.db import models
from django.utils import timezone
from django.utils.encoding import force_text, smart_text
from django.utils.translation import ugettext_lazy as _


class ListFilter(object):
    title = None  # Human-readable title to appear in the right sidebar.
    template = 'admin/filter.html'

    def __init__(self, request, params, model, model_admin):
        # This dictionary will eventually contain the request's query string
        # parameters actually used by this filter.
        self.used_parameters = {}
        if self.title is None:
            raise ImproperlyConfigured(
                "The list filter '%s' does not specify "
                "a 'title'." % self.__class__.__name__)

    def has_output(self):
        """
        Returns True if some choices would be output for this filter.
        """
        raise NotImplementedError('subclasses of ListFilter must provide a has_output() method')

    def choices(self, cl):
        """
        Returns choices ready to be output in the template.
        """
        raise NotImplementedError('subclasses of ListFilter must provide a choices() method')

    def queryset(self, request, queryset):
        """
        Returns the filtered queryset.
        """
        raise NotImplementedError('subclasses of ListFilter must provide a queryset() method')

    def expected_parameters(self):
        """
        Returns the list of parameter names that are expected from the
        request's query string and that will be used by this filter.
        """
        raise NotImplementedError('subclasses of ListFilter must provide an expected_parameters() method')


class SimpleListFilter(ListFilter):
    # The parameter that should be used in the query string for that filter.
    parameter_name = None

    def __init__(self, request, params, model, model_admin):
        super(SimpleListFilter, self).__init__(
            request, params, model, model_admin)
        if self.parameter_name is None:
            raise ImproperlyConfigured(
                "The list filter '%s' does not specify "
                "a 'parameter_name'." % self.__class__.__name__)
        if self.parameter_name in params:
            value = params.pop(self.parameter_name)
            self.used_parameters[self.parameter_name] = value
        lookup_choices = self.lookups(request, model_admin)
        if lookup_choices is None:
            lookup_choices = ()
        self.lookup_choices = list(lookup_choices)

    def has_output(self):
        return len(self.lookup_choices) > 0

    def value(self):
        """
        Returns the value (in string format) provided in the request's
        query string for this filter, if any. If the value wasn't provided then
        returns None.
        """
        return self.used_parameters.get(self.parameter_name)

    def lookups(self, request, model_admin):
        """
        Must be overridden to return a list of tuples (value, verbose value)
        """
        raise NotImplementedError(
            'The SimpleListFilter.lookups() method must be overridden to '
            'return a list of tuples (value, verbose value)')

    def expected_parameters(self):
        return [self.parameter_name]

    def choices(self, cl):
        yield {
            'selected': self.value() is None,
            'query_string': cl.get_query_string({}, [self.parameter_name]),
            'display': _('All'),
        }
        for lookup, title in self.lookup_choices:
            yield {
                'selected': self.value() == force_text(lookup),
                'query_string': cl.get_query_string({
                    self.parameter_name: lookup,
                }, []),
                'display': title,
            }


class FieldListFilter(ListFilter):
    _field_list_filters = []
    _take_priority_index = 0

    def __init__(self, field, request, params, model, model_admin, field_path):
        self.field = field
        self.field_path = field_path
        self.title = getattr(field, 'verbose_name', field_path)
        super(FieldListFilter, self).__init__(
            request, params, model, model_admin)
        for p in self.expected_parameters():
            if p in params:
                value = params.pop(p)
                self.used_parameters[p] = prepare_lookup_value(p, value)

    def has_output(self):
        return True

    def queryset(self, request, queryset):
        try:
            return queryset.filter(**self.used_parameters)
        except ValidationError as e:
            raise IncorrectLookupParameters(e)

    @classmethod
    def register(cls, test, list_filter_class, take_priority=False):
        if take_priority:
            # This is to allow overriding the default filters for certain types
            # of fields with some custom filters. The first found in the list
            # is used in priority.
            cls._field_list_filters.insert(
                cls._take_priority_index, (test, list_filter_class))
            cls._take_priority_index += 1
        else:
            cls._field_list_filters.append((test, list_filter_class))

    @classmethod
    def create(cls, field, request, params, model, model_admin, field_path):
        for test, list_filter_class in cls._field_list_filters:
            if not test(field):
                continue
            return list_filter_class(field, request, params,
                model, model_admin, field_path=field_path)


class RelatedFieldListFilter(FieldListFilter):
    def __init__(self, field, request, params, model, model_admin, field_path):
        other_model = get_model_from_relation(field)
        self.lookup_kwarg = '%s__%s__exact' % (field_path, field.target_field.name)
        self.lookup_kwarg_isnull = '%s__isnull' % field_path
        self.lookup_val = request.GET.get(self.lookup_kwarg)
        self.lookup_val_isnull = request.GET.get(self.lookup_kwarg_isnull)
        self.lookup_choices = self.field_choices(field, request, model_admin)
        super(RelatedFieldListFilter, self).__init__(
            field, request, params, model, model_admin, field_path)
        if hasattr(field, 'verbose_name'):
            self.lookup_title = field.verbose_name
        else:
            self.lookup_title = other_model._meta.verbose_name
        self.title = self.lookup_title
        self.empty_value_display = model_admin.get_empty_value_display()

    @property
    def include_empty_choice(self):
        """
        Return True if a "(None)" choice should be included, which filters
        out everything except empty relationships.
        """
        return self.field.null or (self.field.is_relation and self.field.many_to_many)

    def has_output(self):
        if self.include_empty_choice:
            extra = 1
        else:
            extra = 0
        return len(self.lookup_choices) + extra > 1

    def expected_parameters(self):
        return [self.lookup_kwarg, self.lookup_kwarg_isnull]

    def field_choices(self, field, request, model_admin):
        return field.get_choices(include_blank=False)

    def choices(self, cl):
        yield {
            'selected': self.lookup_val is None and not self.lookup_val_isnull,
            'query_string': cl.get_query_string({},
                [self.lookup_kwarg, self.lookup_kwarg_isnull]),
            'display': _('All'),
        }
        for pk_val, val in self.lookup_choices:
            yield {
                'selected': self.lookup_val == smart_text(pk_val),
                'query_string': cl.get_query_string({
                    self.lookup_kwarg: pk_val,
                }, [self.lookup_kwarg_isnull]),
                'display': val,
            }
        if self.include_empty_choice:
            yield {
                'selected': bool(self.lookup_val_isnull),
                'query_string': cl.get_query_string({
                    self.lookup_kwarg_isnull: 'True',
                }, [self.lookup_kwarg]),
                'display': self.empty_value_display,
            }

FieldListFilter.register(lambda f: f.remote_field, RelatedFieldListFilter)


class BooleanFieldListFilter(FieldListFilter):
    def __init__(self, field, request, params, model, model_admin, field_path):
        self.lookup_kwarg = '%s__exact' % field_path
        self.lookup_kwarg2 = '%s__isnull' % field_path
        self.lookup_val = request.GET.get(self.lookup_kwarg)
        self.lookup_val2 = request.GET.get(self.lookup_kwarg2)
        super(BooleanFieldListFilter, self).__init__(field,
            request, params, model, model_admin, field_path)

    def expected_parameters(self):
        return [self.lookup_kwarg, self.lookup_kwarg2]

    def choices(self, cl):
        for lookup, title in (
                (None, _('All')),
                ('1', _('Yes')),
                ('0', _('No'))):
            yield {
                'selected': self.lookup_val == lookup and not self.lookup_val2,
                'query_string': cl.get_query_string({
                    self.lookup_kwarg: lookup,
                }, [self.lookup_kwarg2]),
                'display': title,
            }
        if isinstance(self.field, models.NullBooleanField):
            yield {
                'selected': self.lookup_val2 == 'True',
                'query_string': cl.get_query_string({
                    self.lookup_kwarg2: 'True',
                }, [self.lookup_kwarg]),
                'display': _('Unknown'),
            }

FieldListFilter.register(lambda f: isinstance(f,
    (models.BooleanField, models.NullBooleanField)), BooleanFieldListFilter)


class ChoicesFieldListFilter(FieldListFilter):
    def __init__(self, field, request, params, model, model_admin, field_path):
        self.lookup_kwarg = '%s__exact' % field_path
        self.lookup_val = request.GET.get(self.lookup_kwarg)
        super(ChoicesFieldListFilter, self).__init__(
            field, request, params, model, model_admin, field_path)

    def expected_parameters(self):
        return [self.lookup_kwarg]

    def choices(self, cl):
        yield {
            'selected': self.lookup_val is None,
            'query_string': cl.get_query_string({}, [self.lookup_kwarg]),
            'display': _('All')
        }
        for lookup, title in self.field.flatchoices:
            yield {
                'selected': smart_text(lookup) == self.lookup_val,
                'query_string': cl.get_query_string({
                    self.lookup_kwarg: lookup}),
                'display': title,
            }

FieldListFilter.register(lambda f: bool(f.choices), ChoicesFieldListFilter)


class DateFieldListFilter(FieldListFilter):
    def __init__(self, field, request, params, model, model_admin, field_path):
        self.field_generic = '%s__' % field_path
        self.date_params = {k: v for k, v in params.items()
                            if k.startswith(self.field_generic)}

        now = timezone.now()
        # When time zone support is enabled, convert "now" to the user's time
        # zone so Django's definition of "Today" matches what the user expects.
        if timezone.is_aware(now):
            now = timezone.localtime(now)

        if isinstance(field, models.DateTimeField):
            today = now.replace(hour=0, minute=0, second=0, microsecond=0)
        else:       # field is a models.DateField
            today = now.date()
        tomorrow = today + datetime.timedelta(days=1)
        if today.month == 12:
            next_month = today.replace(year=today.year + 1, month=1, day=1)
        else:
            next_month = today.replace(month=today.month + 1, day=1)
        next_year = today.replace(year=today.year + 1, month=1, day=1)

        self.lookup_kwarg_since = '%s__gte' % field_path
        self.lookup_kwarg_until = '%s__lt' % field_path
        self.links = (
            (_('Any date'), {}),
            (_('Today'), {
                self.lookup_kwarg_since: str(today),
                self.lookup_kwarg_until: str(tomorrow),
            }),
            (_('Past 7 days'), {
                self.lookup_kwarg_since: str(today - datetime.timedelta(days=7)),
                self.lookup_kwarg_until: str(tomorrow),
            }),
            (_('This month'), {
                self.lookup_kwarg_since: str(today.replace(day=1)),
                self.lookup_kwarg_until: str(next_month),
            }),
            (_('This year'), {
                self.lookup_kwarg_since: str(today.replace(month=1, day=1)),
                self.lookup_kwarg_until: str(next_year),
            }),
        )
        super(DateFieldListFilter, self).__init__(
            field, request, params, model, model_admin, field_path)

    def expected_parameters(self):
        return [self.lookup_kwarg_since, self.lookup_kwarg_until]

    def choices(self, cl):
        for title, param_dict in self.links:
            yield {
                'selected': self.date_params == param_dict,
                'query_string': cl.get_query_string(
                    param_dict, [self.field_generic]),
                'display': title,
            }

FieldListFilter.register(
    lambda f: isinstance(f, models.DateField), DateFieldListFilter)


# This should be registered last, because it's a last resort. For example,
# if a field is eligible to use the BooleanFieldListFilter, that'd be much
# more appropriate, and the AllValuesFieldListFilter won't get used for it.
class AllValuesFieldListFilter(FieldListFilter):
    def __init__(self, field, request, params, model, model_admin, field_path):
        self.lookup_kwarg = field_path
        self.lookup_kwarg_isnull = '%s__isnull' % field_path
        self.lookup_val = request.GET.get(self.lookup_kwarg)
        self.lookup_val_isnull = request.GET.get(self.lookup_kwarg_isnull)
        self.empty_value_display = model_admin.get_empty_value_display()
        parent_model, reverse_path = reverse_field_path(model, field_path)
        # Obey parent ModelAdmin queryset when deciding which options to show
        if model == parent_model:
            queryset = model_admin.get_queryset(request)
        else:
            queryset = parent_model._default_manager.all()
        self.lookup_choices = (queryset
                               .distinct()
                               .order_by(field.name)
                               .values_list(field.name, flat=True))
        super(AllValuesFieldListFilter, self).__init__(
            field, request, params, model, model_admin, field_path)

    def expected_parameters(self):
        return [self.lookup_kwarg, self.lookup_kwarg_isnull]

    def choices(self, cl):
        yield {
            'selected': (self.lookup_val is None
                and self.lookup_val_isnull is None),
            'query_string': cl.get_query_string({},
                [self.lookup_kwarg, self.lookup_kwarg_isnull]),
            'display': _('All'),
        }
        include_none = False
        for val in self.lookup_choices:
            if val is None:
                include_none = True
                continue
            val = smart_text(val)
            yield {
                'selected': self.lookup_val == val,
                'query_string': cl.get_query_string({
                    self.lookup_kwarg: val,
                }, [self.lookup_kwarg_isnull]),
                'display': val,
            }
        if include_none:
            yield {
                'selected': bool(self.lookup_val_isnull),
                'query_string': cl.get_query_string({
                    self.lookup_kwarg_isnull: 'True',
                }, [self.lookup_kwarg]),
                'display': self.empty_value_display,
            }

FieldListFilter.register(lambda f: True, AllValuesFieldListFilter)


class RelatedOnlyFieldListFilter(RelatedFieldListFilter):
    def field_choices(self, field, request, model_admin):
        limit_choices_to = {'pk__in': set(model_admin.get_queryset(request).values_list(field.name, flat=True))}
        return field.get_choices(include_blank=False, limit_choices_to=limit_choices_to)
