from rest_framework import serializers

from apps.shelf_books.models import ShelfBook
from apps.books.models import Book
from apps.shelves.models import Shelf
from apps.shelves.serializers import ShelfSerializer
from apps.books.serializers import BookSerializer

class ShelfBookSerializer(serializers.ModelSerializer):
    shelf = ShelfSerializer(read_only=True)

    book = BookSerializer(read_only=True)
    book_id = serializers.PrimaryKeyRelatedField(
        queryset=Book.objects.all(),
        source="book", 
        write_only=True
    )

    class Meta:
        model = ShelfBook
        fields = [
            "id",
            "shelf",
            "book",
            "book_id",
            "quantity"
        ]
        read_only_fields = ["id"]

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        request = self.context.get("request")        
        if request and request.user and request.user.is_authenticated:
            self.fields["book_id"].queryset = Book.objects.filter(
                user=request.user
            )
        else:
            self.fields["book_id"].queryset = Book.objects.none()
            

    def validate(self, attrs):
        attrs = super().validate(attrs)

        book = attrs.get("book")
        shelf = self.context.get("shelf")

        if not book:
            book = self.instance.book

        if not shelf:
            return attrs

        qs = ShelfBook.objects.filter(
            book=book,
            shelf=shelf
        )
            
        if self.instance:
            qs = qs.exclude(pk=self.instance.pk)

        if qs.exists():
            raise serializers.ValidationError(
                "This Book already exists in shelf!"
            )
                
        if book.user_id != shelf.user_id:
            raise serializers.ValidationError(
                "Book and Shelf must be from the same user!"
            )
        
        return attrs

    def create(self, validated_data):
        shelf = self.context["shelf"]
        validated_data["shelf"] = shelf

        return super().create(validated_data)
    
    def update(self, instance, validated_data):
        shelf = self.context["shelf"]
        validated_data["shelf"] = shelf

        return super().update(instance, validated_data)