from rest_framework import serializers
from decimal import Decimal
from typing import List, Dict, Any
from stock import models as stock_models
from basic_info import models as basic_info_models


class ProductStockChangeSerializer(serializers.Serializer):
    """产品库存变动序列化器"""
    product = serializers.IntegerField(help_text="产品ID")
    quantity = serializers.ListField(
        child=serializers.DecimalField(max_digits=10, decimal_places=2, min_value=Decimal('0.01')),
        min_length=1,
        help_text="数量列表，每个数量对应一条明细记录"
    )

    def validate_product(self, value: int) -> int:
        """验证产品是否存在"""
        try:
            basic_info_models.Product.objects.get(id=value)
        except basic_info_models.Product.DoesNotExist:
            raise serializers.ValidationError(f"产品ID {value} 不存在")
        return value


class CreateStockChangeSerializer(serializers.Serializer):
    """创建库存变动记录序列化器"""
    stock_change_record_id = serializers.IntegerField(
        required=False, 
        allow_null=True,
        help_text="库存变动记录ID，如果不提供则创建新记录"
    )
    products = ProductStockChangeSerializer(many=True, help_text="产品列表")

    def validate_stock_change_record_id(self, value: int) -> int:
        """验证库存变动记录是否存在"""
        if value is not None:
            try:
                stock_models.StockChangeRecord.objects.get(id=value)
            except stock_models.StockChangeRecord.DoesNotExist:
                raise serializers.ValidationError(f"库存变动记录ID {value} 不存在")
        return value

    def validate_products(self, value: List[Dict[str, Any]]) -> List[Dict[str, Any]]:
        """验证产品列表"""
        if not value:
            raise serializers.ValidationError("产品列表不能为空")
        
        # 检查是否有重复的产品ID
        product_ids = [item['product'] for item in value]
        if len(product_ids) != len(set(product_ids)):
            raise serializers.ValidationError("产品列表中存在重复的产品ID")
        
        return value


class StockChangeRecordResponseSerializer(serializers.ModelSerializer):
    """库存变动记录响应序列化器"""
    
    class Meta:
        model = stock_models.StockChangeRecord
        fields = [
            'id', 'type', 'warehouse', 'source_type', 'source_id', 
            'is_finished', 'finished_at', 'created_at', 'updated_at'
        ]


class StockChangeDetailResponseSerializer(serializers.ModelSerializer):
    """库存变动明细响应序列化器"""
    product_name = serializers.CharField(source='product.name', read_only=True)
    unit_display = serializers.CharField(source='get_unit_display', read_only=True)
    
    class Meta:
        model = stock_models.StockChangeDetail
        fields = [
            'id', 'product', 'product_name', 'quantity', 
            'unit', 'unit_display', 'stock_change_record'
        ]


class CreateStockChangeResponseSerializer(serializers.Serializer):
    """创建库存变动记录响应序列化器"""
    stock_change_record = StockChangeRecordResponseSerializer()
    details = StockChangeDetailResponseSerializer(many=True)
    message = serializers.CharField()
    created_details_count = serializers.IntegerField()


class SetMerchantAutoCompleteStockChangeSerializer(serializers.Serializer):
    """设置商户自动确认库存变动序列化器"""
    auto_complete = serializers.BooleanField(
        help_text="是否自动确认库存变动"
    )