""" book list views"""
from typing import Optional

from django.contrib.auth.decorators import login_required
from django.core.paginator import Paginator
from django.db import IntegrityError, transaction
from django.db.models import Avg, Count, Q, Max
from django.db.models.functions import Coalesce
from django.http import HttpResponseNotFound, HttpResponseBadRequest, HttpResponse
from django.shortcuts import get_object_or_404, redirect
from django.template.response import TemplateResponse
from django.utils.decorators import method_decorator
from django.views import View
from django.views.decorators.http import require_POST

from bookwyrm import forms, models
from bookwyrm.activitypub import ActivitypubResponse
from bookwyrm.connectors import connector_manager
from .helpers import is_api_request, privacy_filter
from .helpers import get_user_from_username


# pylint: disable=no-self-use
class Lists(View):
    """ book list page """

    def get(self, request):
        """ display a book list """
        # hide lists with no approved books
        lists = (
            models.List.objects.annotate(
                item_count=Count("listitem", filter=Q(listitem__approved=True))
            )
            .filter(item_count__gt=0)
            .order_by("-updated_date")
            .distinct()
        )

        lists = privacy_filter(
            request.user, lists, privacy_levels=["public", "followers"]
        )

        paginated = Paginator(lists, 12)
        data = {
            "lists": paginated.get_page(request.GET.get("page")),
            "list_form": forms.ListForm(),
            "path": "/list",
        }
        return TemplateResponse(request, "lists/lists.html", data)

    @method_decorator(login_required, name="dispatch")
    # pylint: disable=unused-argument
    def post(self, request):
        """ create a book_list """
        form = forms.ListForm(request.POST)
        if not form.is_valid():
            return redirect("lists")
        book_list = form.save()

        return redirect(book_list.local_path)


class UserLists(View):
    """ a user's book list page """

    def get(self, request, username):
        """ display a book list """
        user = get_user_from_username(request.user, username)
        lists = models.List.objects.filter(user=user)
        lists = privacy_filter(request.user, lists)
        paginated = Paginator(lists, 12)

        data = {
            "user": user,
            "is_self": request.user.id == user.id,
            "lists": paginated.get_page(request.GET.get("page")),
            "list_form": forms.ListForm(),
            "path": user.local_path + "/lists",
        }
        return TemplateResponse(request, "user/lists.html", data)


class List(View):
    """ book list page """

    def get(self, request, list_id):
        """ display a book list """
        book_list = get_object_or_404(models.List, id=list_id)
        if not book_list.visible_to_user(request.user):
            return HttpResponseNotFound()

        if is_api_request(request):
            return ActivitypubResponse(book_list.to_activity(**request.GET))

        query = request.GET.get("q")
        suggestions = None

        # sort_by shall be "order" unless a valid alternative is given
        sort_by = request.GET.get("sort_by", "order")
        if sort_by not in ("order", "title", "rating"):
            sort_by = "order"

        # direction shall be "ascending" unless a valid alternative is given
        direction = request.GET.get("direction", "ascending")
        if direction not in ("ascending", "descending"):
            direction = "ascending"

        internal_sort_by = {
            "order": "order",
            "title": "book__title",
            "rating": "average_rating",
        }
        directional_sort_by = internal_sort_by[sort_by]
        if direction == "descending":
            directional_sort_by = "-" + directional_sort_by

        if sort_by == "order":
            items = book_list.listitem_set.filter(approved=True).order_by(
                directional_sort_by
            )
        elif sort_by == "title":
            items = book_list.listitem_set.filter(approved=True).order_by(
                directional_sort_by
            )
        elif sort_by == "rating":
            items = (
                book_list.listitem_set.annotate(
                    average_rating=Avg(Coalesce("book__review__rating", 0))
                )
                .filter(approved=True)
                .order_by(directional_sort_by)
            )

        paginated = Paginator(items, 12)

        if query and request.user.is_authenticated:
            # search for books
            suggestions = connector_manager.local_search(query, raw=True)
        elif request.user.is_authenticated:
            # just suggest whatever books are nearby
            suggestions = request.user.shelfbook_set.filter(
                ~Q(book__in=book_list.books.all())
            )
            suggestions = [s.book for s in suggestions[:5]]
            if len(suggestions) < 5:
                suggestions += [
                    s.default_edition
                    for s in models.Work.objects.filter(
                        ~Q(editions__in=book_list.books.all()),
                    ).order_by("-updated_date")
                ][: 5 - len(suggestions)]

        data = {
            "list": book_list,
            "items": paginated.get_page(request.GET.get("page")),
            "pending_count": book_list.listitem_set.filter(approved=False).count(),
            "suggested_books": suggestions,
            "list_form": forms.ListForm(instance=book_list),
            "status_form": forms.ListStatusForm(),
            "query": query or "",
            "sort_form": forms.SortListForm(
                {"direction": direction, "sort_by": sort_by}
            ),
        }
        return TemplateResponse(request, "lists/list.html", data)

    @method_decorator(login_required, name="dispatch")
    # pylint: disable=unused-argument
    def post(self, request, list_id):
        """ edit a list """
        book_list = get_object_or_404(models.List, id=list_id)
        form = forms.ListForm(request.POST, instance=book_list)
        if not form.is_valid():
            return redirect("list", book_list.id)
        book_list = form.save()
        return redirect(book_list.local_path)


class Curate(View):
    """ approve or discard list suggestsions """

    @method_decorator(login_required, name="dispatch")
    def get(self, request, list_id):
        """ display a pending list """
        book_list = get_object_or_404(models.List, id=list_id)
        if not book_list.user == request.user:
            # only the creater can curate the list
            return HttpResponseNotFound()

        data = {
            "list": book_list,
            "pending": book_list.listitem_set.filter(approved=False),
            "list_form": forms.ListForm(instance=book_list),
        }
        return TemplateResponse(request, "lists/curate.html", data)

    @method_decorator(login_required, name="dispatch")
    # pylint: disable=unused-argument
    def post(self, request, list_id):
        """ edit a book_list """
        book_list = get_object_or_404(models.List, id=list_id)
        suggestion = get_object_or_404(models.ListItem, id=request.POST.get("item"))
        approved = request.POST.get("approved") == "true"
        if approved:
            # update the book and set it to be the last in the order of approved books,
            # before any pending books
            suggestion.approved = True
            order_max = (
                book_list.listitem_set.filter(approved=True).aggregate(Max("order"))[
                    "order__max"
                ]
                or 0
            ) + 1
            suggestion.order = order_max
            increment_order_in_reverse(book_list.id, order_max)
            suggestion.save()
        else:
            deleted_order = suggestion.order
            suggestion.delete(broadcast=False)
            normalize_book_list_ordering(book_list.id, start=deleted_order)
        return redirect("list-curate", book_list.id)


@require_POST
def add_book(request):
    """ put a book on a list """
    book_list = get_object_or_404(models.List, id=request.POST.get("list"))
    if not book_list.visible_to_user(request.user):
        return HttpResponseNotFound()

    book = get_object_or_404(models.Edition, id=request.POST.get("book"))
    # do you have permission to add to the list?
    try:
        if request.user == book_list.user or book_list.curation == "open":
            # add the book at the latest order of approved books, before pending books
            order_max = (
                book_list.listitem_set.filter(approved=True).aggregate(Max("order"))[
                    "order__max"
                ]
            ) or 0
            increment_order_in_reverse(book_list.id, order_max + 1)
            models.ListItem.objects.create(
                book=book,
                book_list=book_list,
                user=request.user,
                order=order_max + 1,
            )
        elif book_list.curation == "curated":
            # make a pending entry at the end of the list
            order_max = (
                book_list.listitem_set.aggregate(Max("order"))["order__max"]
            ) or 0
            models.ListItem.objects.create(
                approved=False,
                book=book,
                book_list=book_list,
                user=request.user,
                order=order_max + 1,
            )
        else:
            # you can't add to this list, what were you THINKING
            return HttpResponseBadRequest()
    except IntegrityError:
        # if the book is already on the list, don't flip out
        pass

    return redirect("list", book_list.id)


@require_POST
def remove_book(request, list_id):
    """ remove a book from a list """
    with transaction.atomic():
        book_list = get_object_or_404(models.List, id=list_id)
        item = get_object_or_404(models.ListItem, id=request.POST.get("item"))

        if not book_list.user == request.user and not item.user == request.user:
            return HttpResponseNotFound()

        deleted_order = item.order
        item.delete()
    normalize_book_list_ordering(book_list.id, start=deleted_order)
    return redirect("list", list_id)


@require_POST
def set_book_position(request, list_item_id):
    """
    Action for when the list user manually specifies a list position, takes
    special care with the unique ordering per list.
    """
    with transaction.atomic():
        list_item = get_object_or_404(models.ListItem, id=list_item_id)
        try:
            int_position = int(request.POST.get("position"))
        except ValueError:
            return HttpResponseBadRequest(
                "bad value for position. should be an integer"
            )

        if int_position < 1:
            return HttpResponseBadRequest("position cannot be less than 1")

        book_list = list_item.book_list

        # the max position to which a book may be set is the highest order for
        # books which are approved
        order_max = book_list.listitem_set.filter(approved=True).aggregate(
            Max("order")
        )["order__max"]

        if int_position > order_max:
            int_position = order_max

        if request.user not in (book_list.user, list_item.user):
            return HttpResponseNotFound()

        original_order = list_item.order
        if original_order == int_position:
            return HttpResponse(status=204)
        if original_order > int_position:
            list_item.order = -1
            list_item.save()
            increment_order_in_reverse(book_list.id, int_position, original_order)
        else:
            list_item.order = -1
            list_item.save()
            decrement_order(book_list.id, original_order, int_position)

        list_item.order = int_position
        list_item.save()

    return redirect("list", book_list.id)


@transaction.atomic
def increment_order_in_reverse(
    book_list_id: int, start: int, end: Optional[int] = None
):
    """ increase the order nu,ber for every item in a list """
    try:
        book_list = models.List.objects.get(id=book_list_id)
    except models.List.DoesNotExist:
        return
    items = book_list.listitem_set.filter(order__gte=start)
    if end is not None:
        items = items.filter(order__lt=end)
    items = items.order_by("-order")
    for item in items:
        item.order += 1
        item.save()


@transaction.atomic
def decrement_order(book_list_id, start, end):
    """ decrement the order value for every item in a list """
    try:
        book_list = models.List.objects.get(id=book_list_id)
    except models.List.DoesNotExist:
        return
    items = book_list.listitem_set.filter(order__gt=start, order__lte=end).order_by(
        "order"
    )
    for item in items:
        item.order -= 1
        item.save()


@transaction.atomic
def normalize_book_list_ordering(book_list_id, start=0, add_offset=0):
    """ gives each book in a list the proper sequential order number """
    try:
        book_list = models.List.objects.get(id=book_list_id)
    except models.List.DoesNotExist:
        return
    items = book_list.listitem_set.filter(order__gt=start).order_by("order")
    for i, item in enumerate(items, start):
        effective_order = i + add_offset
        if item.order != effective_order:
            item.order = effective_order
            item.save()