import time
from decimal import Decimal

from django import forms
from django.core.validators import MaxValueValidator, MinValueValidator
from django.utils.translation import gettext_lazy as _

from netbox.registry import registry
from utilities.forms.fields import ColorField, QueryField, TagFilterField
from utilities.forms.widgets import FilterModifierWidget
from utilities.forms.widgets.modifiers import MODIFIER_EMPTY_FALSE, MODIFIER_EMPTY_TRUE

__all__ = (
    'BackgroundJobMixin',
    'CheckLastUpdatedMixin',
    'DistanceValidationMixin',
    'FilterModifierMixin',
    'FORM_FIELD_LOOKUPS',
)


# Mapping of form field types to their supported lookups
FORM_FIELD_LOOKUPS = {
    QueryField: [],
    forms.BooleanField: [],
    forms.NullBooleanField: [],
    forms.CharField: [
        ('exact', _('is')),
        ('n', _('is not')),
        ('ic', _('contains')),
        ('isw', _('starts with')),
        ('iew', _('ends with')),
        ('ie', _('equals (case-insensitive)')),
        ('regex', _('matches pattern')),
        ('iregex', _('matches pattern (case-insensitive)')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
    forms.IntegerField: [
        ('exact', _('is')),
        ('n', _('is not')),
        ('gt', _('greater than (>)')),
        ('gte', _('at least (≥)')),
        ('lt', _('less than (<)')),
        ('lte', _('at most (≤)')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
    forms.DecimalField: [
        ('exact', _('is')),
        ('n', _('is not')),
        ('gt', _('greater than (>)')),
        ('gte', _('at least (≥)')),
        ('lt', _('less than (<)')),
        ('lte', _('at most (≤)')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
    forms.DateField: [
        ('exact', _('is')),
        ('n', _('is not')),
        ('gt', _('after')),
        ('gte', _('on or after')),
        ('lt', _('before')),
        ('lte', _('on or before')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
    forms.ModelChoiceField: [
        ('exact', _('is')),
        ('n', _('is not')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
    ColorField: [
        ('exact', _('is')),
        ('n', _('is not')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
    TagFilterField: [
        ('exact', _('has these tags')),
        ('n', _('does not have these tags')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
    forms.ChoiceField: [
        ('exact', _('is')),
        ('n', _('is not')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
    forms.MultipleChoiceField: [
        ('exact', _('is')),
        ('n', _('is not')),
        (MODIFIER_EMPTY_TRUE, _('is empty')),
        (MODIFIER_EMPTY_FALSE, _('is not empty')),
    ],
}


class BackgroundJobMixin(forms.Form):
    background_job = forms.BooleanField(
        label=_('Background job'),
        help_text=_("Execute this task via a background job"),
        required=False,
    )

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

        # Declare background_job a meta field
        if hasattr(self, 'meta_fields'):
            self.meta_fields.append('background_job')
        else:
            self.meta_fields = ['background_job']


class CheckLastUpdatedMixin(forms.Form):
    """
    Checks whether the object being saved has been updated since the form was initialized. If so, validation fails.
    This prevents a user from inadvertently overwriting any changes made to the object between when the form was
    initialized and when it was submitted.

    This validation does not apply to newly created objects, or if the `_init_time` field is not present in the form
    data.
    """
    _init_time = forms.DecimalField(
        initial=time.time,
        required=False,
        widget=forms.HiddenInput()
    )

    def clean(self):
        super().clean()

        # Skip for absent or newly created instances
        if not self.instance or not self.instance.pk:
            return

        # Skip if a form init time has not been specified
        if not (form_init_time := self.cleaned_data.get('_init_time')):
            return

        # Skip if the object does not have a last_updated value
        if not (last_updated := getattr(self.instance, 'last_updated', None)):
            return

        # Check that the submitted initialization time is not earlier than the object's modification time
        if form_init_time < last_updated.timestamp():
            raise forms.ValidationError(_(
                "This object has been modified since the form was rendered. Please consult the object's change "
                "log for details."
            ))


class DistanceValidationMixin(forms.Form):
    distance = forms.DecimalField(
        required=False,
        validators=[
            MinValueValidator(Decimal(0)),
            MaxValueValidator(Decimal(100000)),
        ]
    )


class FilterModifierMixin:
    """
    Mixin that enhances filter form fields with lookup modifier dropdowns.

    Automatically detects fields that could benefit from multiple lookup options
    and wraps their widgets with FilterModifierWidget.
    """

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

    def _enhance_fields_with_modifiers(self):
        """Wrap compatible field widgets with FilterModifierWidget."""

        model = getattr(self, 'model', None)
        if model is None and hasattr(self, '_meta'):
            model = getattr(self._meta, 'model', None)

        filterset_class = None
        if model:
            key = f'{model._meta.app_label}.{model._meta.model_name}'
            filterset_class = registry['filtersets'].get(key)

        filterset = filterset_class() if filterset_class else None

        for field_name, field in self.fields.items():
            lookups = self._get_lookup_choices(field)

            if filterset:
                lookups = self._verify_lookups_with_filterset(field_name, lookups, filterset)

            if len(lookups) > 1:
                field.widget = FilterModifierWidget(
                    widget=field.widget,
                    lookups=lookups
                )

    def _get_lookup_choices(self, field):
        """Determine the available lookup choices for a given field.

        Returns an empty list for fields that should not be enhanced.
        """
        for field_class in field.__class__.__mro__:
            if field_lookups := FORM_FIELD_LOOKUPS.get(field_class):
                return field_lookups

        return []

    def _verify_lookups_with_filterset(self, field_name, lookups, filterset):
        """Verify which lookups are actually supported by the FilterSet."""
        verified_lookups = []

        for lookup_code, lookup_label in lookups:
            if lookup_code in (MODIFIER_EMPTY_TRUE, MODIFIER_EMPTY_FALSE):
                filter_key = f'{field_name}__empty'
            else:
                filter_key = f'{field_name}__{lookup_code}' if lookup_code != 'exact' else field_name

            if filter_key in filterset.filters:
                verified_lookups.append((lookup_code, lookup_label))

        return verified_lookups