from django.db.models import Count
from rest_framework import serializers
from .models import Dish, DishCategory, Order


class DishCategorySerializer(serializers.ModelSerializer):
    """分类序列化器"""
    dish_count = serializers.IntegerField(read_only=True)

    class Meta:
        model = DishCategory
        fields = ['id', 'name', 'icon', 'order', 'dish_count']


class DishSerializer(serializers.ModelSerializer):
    """菜品序列化器"""
    category_name = serializers.CharField(source='category.name', read_only=True)
    category_id = serializers.IntegerField(write_only=True, required=False, allow_null=True)

    class Meta:
        model = Dish
        fields = ['id', 'name', 'category', 'category_name', 'category_id',
                  'cover_image', 'description', 'ingredients', 'view_count',
                  'created_at', 'updated_at']
        read_only_fields = ['created_at', 'updated_at', 'view_count']


class OrderSerializer(serializers.ModelSerializer):
    """订单序列化器"""
    dishes_detail = DishSerializer(source='dishes', many=True, read_only=True)
    ingredients_summary = serializers.SerializerMethodField()
    dish_ids = serializers.ListField(
        child=serializers.IntegerField(),
        write_only=True,
        required=False
    )

    class Meta:
        model = Order
        fields = ['id', 'name', 'dishes', 'dishes_detail', 'dish_ids',
                  'status', 'party_date', 'participants',
                  'created_at', 'completed_at', 'note', 'ingredients_summary', 'images']
        read_only_fields = ['created_at', 'completed_at']
        extra_kwargs = {
            'dishes': {'required': False}
        }

    def get_ingredients_summary(self, obj):
        # Compute in Python using prefetched dishes (avoids N+1)
        summary = {}
        for dish in obj.dishes.all():
            for ing in dish.ingredients:
                name = ing.get('name', '').strip()
                amount = ing.get('amount', '').strip()
                if name:
                    if name in summary:
                        if amount:
                            summary[name] += f" + {amount}"
                    else:
                        summary[name] = amount
        return [{'name': k, 'amount': v} for k, v in summary.items()]


    def create(self, validated_data):
        dish_ids = validated_data.pop('dish_ids', [])
        order = Order.objects.create(**validated_data)
        if dish_ids:
            dishes = Dish.objects.filter(id__in=dish_ids)
            order.dishes.set(dishes)
        return order

    def update(self, instance, validated_data):
        dish_ids = validated_data.pop('dish_ids', None)
        for attr, value in validated_data.items():
            setattr(instance, attr, value)
        instance.save()
        if dish_ids is not None:
            dishes = Dish.objects.filter(id__in=dish_ids)
            instance.dishes.set(dishes)
        return instance