""" book list views"""
from typing import Optional
from urllib.parse import urlencode

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, DecimalField, Q, Max
from django.db.models.functions import Coalesce
from django.http import HttpResponseBadRequest, HttpResponse
from django.shortcuts import get_object_or_404, redirect
from django.template.response import TemplateResponse
from django.urls import reverse
from django.utils.decorators import method_decorator
from django.views import View
from django.views.decorators.http import require_POST

from bookwyrm import book_search, forms, models
from bookwyrm.activitypub import ActivitypubResponse
from bookwyrm.settings import PAGE_LENGTH
from bookwyrm.views.helpers import is_api_request


# pylint: disable=no-self-use
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)
        book_list.raise_visible_to_user(request.user)

        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"

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

        items = book_list.listitem_set.prefetch_related("user", "book", "book__authors")
        if sort_by == "rating":
            items = items.annotate(
                average_rating=Avg(
                    Coalesce("book__review__rating", 0.0),
                    output_field=DecimalField(),
                )
            )
        items = items.filter(approved=True).order_by(directional_sort_by)

        paginated = Paginator(items, PAGE_LENGTH)

        if query and request.user.is_authenticated:
            # search for books
            suggestions = book_search.search(
                query,
                filters=[~Q(parent_work__editions__in=book_list.books.all())],
            )
        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)]

        page = paginated.get_page(request.GET.get("page"))

        embed_key = str(book_list.embed_key.hex)
        embed_url = reverse("embed-list", args=[book_list.id, embed_key])
        embed_url = request.build_absolute_uri(embed_url)

        if request.GET:
            embed_url = f"{embed_url}?{request.GET.urlencode()}"

        data = {
            "list": book_list,
            "items": page,
            "page_range": paginated.get_elided_page_range(
                page.number, on_each_side=2, on_ends=1
            ),
            "pending_count": book_list.listitem_set.filter(approved=False).count(),
            "suggested_books": suggestions,
            "list_form": forms.ListForm(instance=book_list),
            "query": query or "",
            "sort_form": forms.SortListForm(
                {"direction": direction, "sort_by": sort_by}
            ),
            "embed_url": embed_url,
        }
        return TemplateResponse(request, "lists/list.html", data)

    @method_decorator(login_required, name="dispatch")
    def post(self, request, list_id):
        """edit a list"""
        book_list = get_object_or_404(models.List, id=list_id)
        book_list.raise_not_editable(request.user)

        form = forms.ListForm(request.POST, instance=book_list)
        if not form.is_valid():
            return redirect("list", book_list.id)
        book_list = form.save()
        if not book_list.curation == "group":
            book_list.group = None
            book_list.save(broadcast=False)

        return redirect(book_list.local_path)


@require_POST
@login_required
def save_list(request, list_id):
    """save a list"""
    book_list = get_object_or_404(models.List, id=list_id)
    request.user.saved_lists.add(book_list)
    return redirect("list", list_id)


@require_POST
@login_required
def unsave_list(request, list_id):
    """unsave a list"""
    book_list = get_object_or_404(models.List, id=list_id)
    request.user.saved_lists.remove(book_list)
    return redirect("list", list_id)


@require_POST
@login_required
def delete_list(request, list_id):
    """delete a list"""
    book_list = get_object_or_404(models.List, id=list_id)

    # only the owner or a moderator can delete a list
    book_list.raise_not_deletable(request.user)

    book_list.delete()
    return redirect("lists")


@require_POST
@login_required
@transaction.atomic
def add_book(request):
    """put a book on a list"""
    book_list = get_object_or_404(models.List, id=request.POST.get("book_list"))
    # make sure the user is allowed to submit to this list
    book_list.raise_not_submittable(request.user)

    form = forms.ListItemForm(request.POST)
    if not form.is_valid():
        # this shouldn't happen, there aren't validated fields
        raise Exception(form.errors)
    item = form.save(commit=False)

    if 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
        item.approved = False
    else:
        # 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)
    item.order = order_max + 1

    try:
        item.save()
    except IntegrityError:
        # if the book is already on the list, don't flip out
        pass

    path = reverse("list", args=[book_list.id])
    params = request.GET.copy()
    params["updated"] = True
    return redirect(f"{path}?{urlencode(params)}")


@require_POST
@login_required
def remove_book(request, list_id):
    """remove a book from a list"""

    book_list = get_object_or_404(models.List, id=list_id)
    item = get_object_or_404(models.ListItem, id=request.POST.get("item"))

    item.raise_not_deletable(request.user)

    with transaction.atomic():
        deleted_order = item.order
        item.delete()
        normalize_book_list_ordering(book_list.id, start=deleted_order)

    return redirect("list", list_id)


@require_POST
@login_required
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.
    """
    list_item = get_object_or_404(models.ListItem, id=list_item_id)
    list_item.book_list.raise_not_editable(request.user)
    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"
    ]

    int_position = min(int_position, order_max)

    original_order = list_item.order
    if original_order == int_position:
        # no change
        return HttpResponse(status=204)

    with transaction.atomic():
        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 number 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()