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
from . import models as api_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"
    )


# ==================== 通用文件上传序列化器 ====================

class UploadedFileSerializer(serializers.ModelSerializer):
    """上传文件序列化器"""
    file_url = serializers.SerializerMethodField()
    owner_username = serializers.CharField(source='owner.username', read_only=True)
    
    class Meta:
        model = api_models.UploadedFile
        fields = [
            'id', 'path', 'file_url', 'original_filename', 'file_size',
            'content_type', 'owner', 'owner_username', 'is_deleted',
            'created_at', 'updated_at'
        ]
        read_only_fields = ['id', 'owner', 'file_size', 'content_type', 'created_at', 'updated_at']
    
    def get_file_url(self, obj):
        """获取文件完整URL"""
        if obj.path:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.path.url)
            return obj.path.url
        return None


class FileUploadSerializer(serializers.Serializer):
    """文件上传请求序列化器"""
    file = serializers.FileField(
        required=True,
        help_text='要上传的文件'
    )
    
    def validate_file(self, value):
        """验证文件"""
        # 限制文件大小为 100MB
        max_size = 100 * 1024 * 1024
        if value.size > max_size:
            raise serializers.ValidationError(f'文件大小不能超过 {max_size // (1024*1024)}MB')
        
        return value