from __future__ import annotations

from django.db import models
from django.db.models import QuerySet
from rest_framework import status, viewsets
from rest_framework.decorators import action
from rest_framework.permissions import IsAuthenticated
from rest_framework.request import Request
from rest_framework.response import Response

from books.models import Book, ReadingStatus
from books.serializers import BookDetailSerializer, BookListSerializer


class BookViewSet(viewsets.ModelViewSet):
    """
    ViewSet for managing books in the user's library.

    Provides:
    - list / retrieve / create / update / partial_update / destroy
    - `mark_finished` action to set a book as 100% complete
    - `stats` action for library overview counts
    """

    permission_classes = [IsAuthenticated]

    def get_serializer_class(self) -> type:
        if self.action == "list":
            return BookListSerializer
        return BookDetailSerializer

    def get_queryset(self) -> QuerySet[Book]:
        """Return books owned by the current user with optimised queries."""
        qs = Book.objects.filter(owner=self.request.user).select_related("owner")

        # Sorting
        sort_by = self.request.query_params.get("sort_by", "-updated_at")
        allowed_sorts = {
            "title": "title",
            "-title": "-title",
            "author": "author",
            "-author": "-author",
            "created_at": "created_at",
            "-created_at": "-created_at",
            "updated_at": "updated_at",
            "-updated_at": "-updated_at",
            "reading_progress": "current_page",  # approximate sort by pages read
            "-reading_progress": "-current_page",
        }
        if sort_by in allowed_sorts:
            qs = qs.order_by(allowed_sorts[sort_by])

        # Filtering
        status_filter = self.request.query_params.get("reading_status", None)
        if status_filter in ReadingStatus.values:
            qs = qs.filter(reading_status=status_filter)

        search = self.request.query_params.get("search", "").strip()
        if search:
            qs = qs.filter(
                models.Q(title__icontains=search) | models.Q(author__icontains=search)
            )

        return qs

    def perform_create(self, serializer: BookDetailSerializer) -> None:
        """Set the owner to the current user on creation."""
        serializer.save(owner=self.request.user)

    @action(detail=True, methods=["post"])
    def mark_finished(self, request: Request, pk: int | None = None) -> Response:
        """Mark a book as finished (100% progress)."""
        book: Book = self.get_object()
        book.mark_as_finished()
        serializer = self.get_serializer(book)
        return Response(serializer.data, status=status.HTTP_200_OK)

    @action(detail=False, methods=["get"])
    def stats(self, request: Request) -> Response:
        """Return aggregate stats about the user's library."""
        qs = self.get_queryset()
        total = qs.count()
        finished = qs.filter(reading_status=ReadingStatus.FINISHED).count()
        reading = qs.filter(reading_status=ReadingStatus.READING).count()
        not_started = qs.filter(reading_status=ReadingStatus.NOT_STARTED).count()
        return Response({
            "total_books": total,
            "finished": finished,
            "reading": reading,
            "not_started": not_started,
        })