import django_filters
from copy import deepcopy
from django.contrib.contenttypes.models import ContentType
from django.db import models
from django_filters.utils import get_model_field, resolve_field

from dcim.forms import MACAddressField
from extras.choices import CustomFieldFilterLogicChoices
from extras.filters import CustomFieldFilter, TagFilter
from extras.models import CustomField
from utilities.constants import (
    FILTER_CHAR_BASED_LOOKUP_MAP, FILTER_NEGATION_LOOKUP_MAP, FILTER_TREENODE_NEGATION_LOOKUP_MAP,
    FILTER_NUMERIC_BASED_LOOKUP_MAP
)
from utilities import filters


__all__ = (
    'BaseFilterSet',
    'ChangeLoggedModelFilterSet',
    'OrganizationalModelFilterSet',
    'PrimaryModelFilterSet',
)


#
# FilterSets
#

class BaseFilterSet(django_filters.FilterSet):
    """
    A base FilterSet which provides common functionality to all NetBox FilterSets
    """
    FILTER_DEFAULTS = deepcopy(django_filters.filterset.FILTER_FOR_DBFIELD_DEFAULTS)
    FILTER_DEFAULTS.update({
        models.AutoField: {
            'filter_class': filters.MultiValueNumberFilter
        },
        models.CharField: {
            'filter_class': filters.MultiValueCharFilter
        },
        models.DateField: {
            'filter_class': filters.MultiValueDateFilter
        },
        models.DateTimeField: {
            'filter_class': filters.MultiValueDateTimeFilter
        },
        models.DecimalField: {
            'filter_class': filters.MultiValueNumberFilter
        },
        models.EmailField: {
            'filter_class': filters.MultiValueCharFilter
        },
        models.FloatField: {
            'filter_class': filters.MultiValueNumberFilter
        },
        models.IntegerField: {
            'filter_class': filters.MultiValueNumberFilter
        },
        models.PositiveIntegerField: {
            'filter_class': filters.MultiValueNumberFilter
        },
        models.PositiveSmallIntegerField: {
            'filter_class': filters.MultiValueNumberFilter
        },
        models.SlugField: {
            'filter_class': filters.MultiValueCharFilter
        },
        models.SmallIntegerField: {
            'filter_class': filters.MultiValueNumberFilter
        },
        models.TimeField: {
            'filter_class': filters.MultiValueTimeFilter
        },
        models.URLField: {
            'filter_class': filters.MultiValueCharFilter
        },
        MACAddressField: {
            'filter_class': filters.MultiValueMACAddressFilter
        },
    })

    @staticmethod
    def _get_filter_lookup_dict(existing_filter):
        # Choose the lookup expression map based on the filter type
        if isinstance(existing_filter, (
            filters.MultiValueDateFilter,
            filters.MultiValueDateTimeFilter,
            filters.MultiValueNumberFilter,
            filters.MultiValueTimeFilter
        )):
            return FILTER_NUMERIC_BASED_LOOKUP_MAP

        elif isinstance(existing_filter, (
            filters.TreeNodeMultipleChoiceFilter,
        )):
            # TreeNodeMultipleChoiceFilter only support negation but must maintain the `in` lookup expression
            return FILTER_TREENODE_NEGATION_LOOKUP_MAP

        elif isinstance(existing_filter, (
            django_filters.ModelChoiceFilter,
            django_filters.ModelMultipleChoiceFilter,
            TagFilter
        )) or existing_filter.extra.get('choices'):
            # These filter types support only negation
            return FILTER_NEGATION_LOOKUP_MAP

        elif isinstance(existing_filter, (
            django_filters.filters.CharFilter,
            django_filters.MultipleChoiceFilter,
            filters.MultiValueCharFilter,
            filters.MultiValueMACAddressFilter
        )):
            return FILTER_CHAR_BASED_LOOKUP_MAP

        return None

    @classmethod
    def get_filters(cls):
        """
        Override filter generation to support dynamic lookup expressions for certain filter types.

        For specific filter types, new filters are created based on defined lookup expressions in
        the form `<field_name>__<lookup_expr>`
        """
        filters = super().get_filters()

        new_filters = {}
        for existing_filter_name, existing_filter in filters.items():
            # Loop over existing filters to extract metadata by which to create new filters

            # If the filter makes use of a custom filter method or lookup expression skip it
            # as we cannot sanely handle these cases in a generic mannor
            if existing_filter.method is not None or existing_filter.lookup_expr not in ['exact', 'in']:
                continue

            # Choose the lookup expression map based on the filter type
            lookup_map = cls._get_filter_lookup_dict(existing_filter)
            if lookup_map is None:
                # Do not augment this filter type with more lookup expressions
                continue

            # Get properties of the existing filter for later use
            field_name = existing_filter.field_name
            field = get_model_field(cls._meta.model, field_name)

            # Create new filters for each lookup expression in the map
            for lookup_name, lookup_expr in lookup_map.items():
                new_filter_name = '{}__{}'.format(existing_filter_name, lookup_name)

                try:
                    if existing_filter_name in cls.declared_filters:
                        # The filter field has been explicity defined on the filterset class so we must manually
                        # create the new filter with the same type because there is no guarantee the defined type
                        # is the same as the default type for the field
                        resolve_field(field, lookup_expr)  # Will raise FieldLookupError if the lookup is invalid
                        new_filter = type(existing_filter)(
                            field_name=field_name,
                            lookup_expr=lookup_expr,
                            label=existing_filter.label,
                            exclude=existing_filter.exclude,
                            distinct=existing_filter.distinct,
                            **existing_filter.extra
                        )
                    else:
                        # The filter field is listed in Meta.fields so we can safely rely on default behaviour
                        # Will raise FieldLookupError if the lookup is invalid
                        new_filter = cls.filter_for_field(field, field_name, lookup_expr)
                except django_filters.exceptions.FieldLookupError:
                    # The filter could not be created because the lookup expression is not supported on the field
                    continue

                if lookup_name.startswith('n'):
                    # This is a negation filter which requires a queryset.exclude() clause
                    # Of course setting the negation of the existing filter's exclude attribute handles both cases
                    new_filter.exclude = not existing_filter.exclude

                new_filters[new_filter_name] = new_filter

        filters.update(new_filters)
        return filters


class ChangeLoggedModelFilterSet(BaseFilterSet):
    created = django_filters.DateFilter()
    created__gte = django_filters.DateFilter(
        field_name='created',
        lookup_expr='gte'
    )
    created__lte = django_filters.DateFilter(
        field_name='created',
        lookup_expr='lte'
    )
    last_updated = django_filters.DateTimeFilter()
    last_updated__gte = django_filters.DateTimeFilter(
        field_name='last_updated',
        lookup_expr='gte'
    )
    last_updated__lte = django_filters.DateTimeFilter(
        field_name='last_updated',
        lookup_expr='lte'
    )


class PrimaryModelFilterSet(ChangeLoggedModelFilterSet):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        # Dynamically add a Filter for each CustomField applicable to the parent model
        custom_fields = CustomField.objects.filter(
            content_types=ContentType.objects.get_for_model(self._meta.model)
        ).exclude(
            filter_logic=CustomFieldFilterLogicChoices.FILTER_DISABLED
        )
        for cf in custom_fields:
            self.filters['cf_{}'.format(cf.name)] = CustomFieldFilter(field_name=cf.name, custom_field=cf)


class OrganizationalModelFilterSet(PrimaryModelFilterSet):
    """
    A base class for adding the search method to models which only expose the `name` and `slug` fields
    """
    q = django_filters.CharFilter(
        method='search',
        label='Search',
    )

    def search(self, queryset, name, value):
        if not value.strip():
            return queryset
        return queryset.filter(
            models.Q(name__icontains=value) |
            models.Q(slug__icontains=value)
        )
