djadhere/stocking/admin.py

from django.contrib import admin
from django.utils.html import format_html
from django.urls import reverse

from mptt.admin import MPTTModelAdmin

from .models import Equipment, Category, Location


class EquipmentInline(admin.StackedInline):
    model = Equipment
    list_display = ('location', 'category', 'quantity',)


class CategoryFilter(admin.SimpleListFilter):
    title = 'Catégorie'
    parameter_name = 'category'

    def lookups(self, request, model_admin):
        return [ (c.pk, '    ' * c.get_level() + c.name) for c in Category.objects.all() ]
    
    def queryset(self, request, queryset):
        try:
            category = Category.objects.get(pk=int(self.value()))
        except (TypeError, ValueError, Category.DoesNotExist):
            pass
        else:
            categories = category.get_descendants(include_self=True)
            queryset = queryset.filter(category__in=categories)
        return queryset


class CategoryAdmin(MPTTModelAdmin):
    search_fields = ['name']
    list_display = ('__str__', 'equipement_list_link',)

    def equipement_list_link(self, category):
        url = reverse('admin:%s_%s_changelist' % (Equipment._meta.app_label, Equipment._meta.model_name))
        url += '?category=%d' % category.pk
        return format_html(u'<a href="{}">{}</a>', url, 'voir la liste des équipements')
    equipement_list_link.short_description = 'Équipements'

    def get_actions(self, request):
        actions = super().get_actions(request)
        if 'delete_selected' in actions:
            del actions['delete_selected']
        return actions

    def has_delete_permission(self, request, obj=None):
        # Interdiction de supprimer la catégorie si elle contient des équipements
        return obj and not Equipment.objects.filter(category__in=obj.get_descendants(include_self=True)).exists()


class LocationAdmin(admin.ModelAdmin):
    list_display = ('__str__', 'equipement_list_link',)
    inlines = (EquipmentInline,)

    def equipement_list_link(self, location):
        url = reverse('admin:%s_%s_changelist' % (Equipment._meta.app_label, Equipment._meta.model_name))
        url += '?location__id__exact=%d' % location.pk
        return format_html(u'<a href="{}">{}</a>', url, 'voir la liste des équipements')
    equipement_list_link.short_description = 'Équipements'

    def get_actions(self, request):
        actions = super().get_actions(request)
        if 'delete_selected' in actions:
            del actions['delete_selected']
        return actions

    def has_delete_permission(self, request, obj=None):
        # Interdiction de supprimer l’emplacement si il contient des équipements
        return obj and not obj.equipment_set.exists()


class EquipmentAdmin(admin.ModelAdmin):
    list_display = ('location', 'category', 'quantity',)
    list_display_links = ('location', 'category',)
    list_editable = ('quantity',)
    list_filter = (
        ('location', admin.RelatedOnlyFieldListFilter),
        CategoryFilter,
    )

    def get_actions(self, request):
        actions = super().get_actions(request)
        if 'delete_selected' in actions:
            del actions['delete_selected']
        return actions

    def has_delete_permission(self, request, obj=None):
        # Interdiction de supprimer le stock d’équipements s’il n’est pas vide
        return obj and obj.quantity == 0


admin.site.register(Category, CategoryAdmin)
admin.site.register(Location, LocationAdmin)
admin.site.register(Equipment, EquipmentAdmin)