from django.conf import settings
from django.core.exceptions import PermissionDenied
from django.db import transaction
from django.shortcuts import get_object_or_404, redirect
from django.template.response import TemplateResponse
from django.urls import reverse
from django.utils.translation import gettext as _

from wagtail import hooks
from wagtail.actions.delete_page import DeletePageAction
from wagtail.admin import messages
from wagtail.admin.utils import get_valid_next_url_from_request
from wagtail.models import Page, ReferenceIndex


def delete(request, page_id):
    page = get_object_or_404(Page, id=page_id).specific
    if not page.permissions_for_user(request.user).can_delete():
        raise PermissionDenied

    wagtail_site_name = getattr(settings, "WAGTAIL_SITE_NAME", "wagtail")
    with transaction.atomic():
        for fn in hooks.get_hooks("before_delete_page"):
            result = fn(request, page)
            if hasattr(result, "status_code"):
                return result

        next_url = get_valid_next_url_from_request(request)

        pages_to_delete = {page}

        # The `construct_translated_pages_to_cascade_actions` hook returns translation and
        # alias pages when the action is set to "delete"
        if getattr(settings, "WAGTAIL_I18N_ENABLED", False):
            for fn in hooks.get_hooks("construct_translated_pages_to_cascade_actions"):
                fn_pages = fn([page], "delete")
                if fn_pages and isinstance(fn_pages, dict):
                    for additional_pages in fn_pages.values():
                        pages_to_delete.update(additional_pages)

        pages_to_delete = list(pages_to_delete)

        if request.method == "POST":
            continue_deleting = True
            if (
                request.POST.get("confirm_site_name")
                and request.POST.get("confirm_site_name") != wagtail_site_name
            ):
                messages.error(
                    request, f"Please type '{wagtail_site_name}' to confirm."
                )
                continue_deleting = False
            if continue_deleting:
                parent_id = page.get_parent().id
                # Delete the source page.
                action = DeletePageAction(page, user=request.user)
                # Permission checks are done above, so skip them in execute.
                action.execute(skip_permission_checks=True)

                # Delete translation and alias pages if they have the same parent page.
                if getattr(settings, "WAGTAIL_I18N_ENABLED", False):
                    parent_page_translations = page.get_parent().get_translations()
                    for page_or_alias in pages_to_delete:
                        if page_or_alias.get_parent() in parent_page_translations:
                            action = DeletePageAction(page_or_alias, user=request.user)
                            # Permission checks are done above, so skip them in execute.
                            action.execute(skip_permission_checks=True)

                messages.success(
                    request,
                    _("Page '%(page_title)s' deleted.")
                    % {"page_title": page.get_admin_display_title()},
                )

                for fn in hooks.get_hooks("after_delete_page"):
                    result = fn(request, page)
                    if hasattr(result, "status_code"):
                        return result

                if next_url:
                    return redirect(next_url)
                return redirect("wagtailadmin_explore", parent_id)

    usage = ReferenceIndex.get_references_to(page).group_by_source_object()
    descendant_count = page.get_descendant_count()
    return TemplateResponse(
        request,
        "wagtailadmin/pages/confirm_delete.html",
        {
            "page": page,
            "descendant_count": descendant_count,
            "next": next_url,
            "model_opts": page._meta,
            "usage_url": reverse("wagtailadmin_pages:usage", args=(page.id,))
            + "?describe_on_delete=1",
            "usage_count": usage.count(),
            "is_protected": usage.is_protected,
            # if the number of pages ( child pages + current page) exceeds this limit, then confirm before delete.
            "confirm_before_delete": (descendant_count + 1)
            >= getattr(settings, "WAGTAILADMIN_UNSAFE_PAGE_DELETION_LIMIT", 10),
            "wagtail_site_name": wagtail_site_name,
            # note that while pages_to_delete may contain a mix of translated pages
            # and aliases, we count the "translations" only, as aliases are similar
            # to symlinks, so they should just follow the source
            "translation_count": len(
                [
                    translation.id
                    for translation in pages_to_delete
                    if not translation.alias_of_id and translation.id != page.id
                ]
            ),
            "translation_descendant_count": sum(
                [
                    translation.get_descendants().filter(alias_of__isnull=True).count()
                    for translation in pages_to_delete
                ]
            ),
        },
    )
