from functools import update_wrapper
from django.contrib.admin import ModelAdmin, helpers
from django.contrib.admin.utils import flatten_fieldsets
from django.forms.formsets import all_valid
from django.urls import reverse, path
from django.core.exceptions import PermissionDenied


class CloneModelAdmin(ModelAdmin):
    clone_verbose_name = "Clone"
    change_form_template = 'admin/admin_change_form.html'
    cloneable_fields = []

    def get_urls(self):

        # Not certain what this wrap() function is exactly. Just copied it from the django admin get_urls function
        def wrap(view):
            def wrapper(*args, **kwargs):
                return self.admin_site.admin_view(view)(*args, **kwargs)

            wrapper.model_admin = self
            return update_wrapper(wrapper, view)

        info = self.opts.app_label, self.opts.model_name

        new_urlpatterns = [
            path(
                "<path:object_id>/clone/",
                wrap(self.clone_view),
                name="%s_%s_clone" % info,
            ),
        ]

        original_urlpatterns = super(CloneModelAdmin, self).get_urls()

        # Important to add custom urls before the existing ones.
        # Last entry is <URLPattern '<path:object_id>/'> which will catch everything not already picked up
        return new_urlpatterns + original_urlpatterns

    def change_view(self, request, object_id, form_url='', extra_context=None):
        url = reverse("admin:{0}_{1}_clone".format(self.opts.app_label, self.opts.model_name), args=[object_id])

        extra_context = extra_context or {}
        extra_context.update({
            'clone_verbose_name': self.clone_verbose_name,
            'clone_link': url,
        })
        return super(CloneModelAdmin, self).change_view(request, object_id, form_url, extra_context)

    def clone_view(self, request, object_id, form_url='', extra_context=None):
        if not self.has_add_permission(request):
            raise PermissionDenied

        original_obj = self.get_object(request, object_id)

        if original_obj is None:
            return self._get_obj_does_not_exist_redirect(
                request, self.opts, object_id
            )

        fieldsets = self.get_fieldsets(request, None)

        model_form = self.get_form(
            request, None, change=False, fields=flatten_fieldsets(fieldsets)
        )

        if request.method == "POST":
            form = model_form(request.POST)
            formsets, inline_instances = self._create_formsets(
                request,
                form.instance,
                change=False,
            )
            form_validated = form.is_valid()
            if form_validated:
                new_object = self.save_form(request, form, change=False)
            else:
                new_object = form.instance

            if all_valid(formsets) and form_validated:
                self.save_model(request, new_object, form, False)
                self.save_related(request, form, formsets, False)
                change_message = self.construct_change_message(
                    request, form, formsets, False
                )
                self.log_addition(request, new_object, change_message)
                return self.response_add(request, new_object)
            else:
                form_validated = False

        else:
            new_obj = self.model()
            for field in self.cloneable_fields:
                setattr(new_obj, field, getattr(original_obj, field))
            form = model_form(instance=new_obj)

            formsets, inline_instances = self._create_formsets(
                request, new_obj, change=True
            )

        admin_form = helpers.AdminForm(
            form,
            list(self.get_fieldsets(request)),
            self.get_prepopulated_fields(request),
            self.readonly_fields,
            model_admin=self
        )
        media = self.media

        inline_formsets = self.get_inline_formsets(
            request, formsets, inline_instances
        )
        for inline_formset in inline_formsets:
            media += inline_formset.media

        title = u'{0} {1}'.format(self.clone_verbose_name, original_obj)

        context = {
            **self.admin_site.each_context(request),
            "title": title,
            "original": title,
            "adminform": admin_form,
            "is_popup": "_popup" in request.POST or "_popup" in request.GET,
            "show_delete": False,
            "media": media,
            "inline_admin_formsets": inline_formsets,
            "errors": helpers.AdminErrorList(form, formsets),
            **(extra_context or {}),
        }

        context.update(extra_context or {})

        return self.render_change_form(
            request,
            context,
            form_url=form_url,
            change=False,
            add=True
        )