"""
Shipment API 序列化器
"""
from rest_framework import serializers

from shipment.models import ExternalFinishedProduct, SalesItem, Shipment


class ShipmentSerializer(serializers.ModelSerializer):
    """
    出货单序列化器（只读，用于返回数据）
    """
    customer_name = serializers.CharField(source='customer.name', read_only=True)
    created_by_id = serializers.IntegerField(source='created_by.id', read_only=True, allow_null=True)
    created_by_name = serializers.SerializerMethodField()
    items_count = serializers.SerializerMethodField()
    cancelled_by_id = serializers.IntegerField(source='cancelled_by.id', read_only=True, allow_null=True)
    cancelled_by_name = serializers.SerializerMethodField()
    status_display = serializers.CharField(source='get_status_display', read_only=True)
    external_finished_products_count = serializers.SerializerMethodField()
    merchant_id = serializers.IntegerField(source='merchant.id', read_only=True)
    merchant_name = serializers.CharField(source='merchant.name', read_only=True)
    sales_items = serializers.SerializerMethodField()
    external_finished_products = serializers.SerializerMethodField()
    
    class Meta:
        model = Shipment
        fields = [
            'id', 'merchant_id', 'merchant_name',
            'customer', 'customer_name', 'shipment_date', 'remark',
            'status', 'status_display',
            'external_id',
            'cancelled_at', 'cancelled_by_id', 'cancelled_by_name',
            'items_count', 'created_by_id', 'created_by_name',
            'external_finished_products_count',
            'sales_items',
            'external_finished_products',
            'created_at', 'updated_at'
        ]
        read_only_fields = ['id', 'created_at', 'updated_at']
    
    def get_created_by_name(self, obj):
        if obj.created_by:
            employee = getattr(obj.created_by, 'employee', None)
            if employee:
                return employee.name
            return obj.created_by.username
        return None
    
    def get_items_count(self, obj):
        return obj.items.count()

    def get_cancelled_by_name(self, obj):
        if obj.cancelled_by:
            employee = getattr(obj.cancelled_by, 'employee', None)
            if employee:
                return employee.name
            return obj.cancelled_by.username
        return None

    def get_external_finished_products_count(self, obj):
        return obj.external_finished_products.count()

    def get_sales_items(self, obj):
        """
        出货单关联的销售品明细（无则返回空数组）。
        """
        # 优先使用 prefetch 的 related manager；兜底为 none()
        rel = getattr(obj, 'items', None)
        items = list(rel.all()) if rel is not None else []
        return SalesItemSerializer(items, many=True).data

    def get_external_finished_products(self, obj):
        """
        出货单关联的外部成品表明细（无则返回空数组）。
        """
        rel = getattr(obj, 'external_finished_products', None)
        products = list(rel.all()) if rel is not None else []
        return ExternalFinishedProductSerializer(products, many=True).data


class ExternalFinishedProductSerializer(serializers.ModelSerializer):
    """
    外部成品表序列化器（只读）
    """
    created_by_id = serializers.IntegerField(source='created_by.id', read_only=True, allow_null=True)
    created_by_name = serializers.SerializerMethodField()

    class Meta:
        model = ExternalFinishedProduct
        fields = [
            'id',
            'style_name',
            'num_of_rolls',
            'remark',
            'created_at',
            'created_by_id',
            'created_by_name',
        ]
        read_only_fields = fields

    def get_created_by_name(self, obj):
        if obj.created_by:
            employee = getattr(obj.created_by, 'employee', None)
            if employee:
                return employee.name
            return obj.created_by.username
        return None


class ShipmentCreateNormalSerializer(serializers.Serializer):
    """
    出货单创建序列化器（普通版）
    """
    customer = serializers.IntegerField(help_text='客户ID')
    shipment_date = serializers.DateField(help_text='出货日期')
    remark = serializers.CharField(required=False, default='', allow_blank=True, help_text='备注')
    sales_items = serializers.ListField(
        child=serializers.IntegerField(),
        required=False,
        default=list,
        help_text='要关联的销售品ID列表'
    )
    
    def validate_sales_items(self, value):
        # 去重
        return list(set(value)) if value else []

class ExternalFinishedProductInputSerializer(serializers.Serializer):
    """外部成品表写入结构（external create 专用）"""
    style_name = serializers.CharField(max_length=200)
    num_of_rolls = serializers.IntegerField(min_value=0)
    remark = serializers.CharField(max_length=200, required=False, allow_blank=True, allow_null=True, default='')


class ShipmentCreateExternalSerializer(serializers.Serializer):
    """
    出货单创建序列化器（external 版）
    
    特点：
    - 不绑定任何 SalesItem
    - 必须提供 external_id
    - 同时写入 ExternalFinishedProduct 列表并关联到 Shipment
    """
    customer = serializers.IntegerField(help_text='客户ID')
    shipment_date = serializers.DateField(help_text='出货日期')
    remark = serializers.CharField(required=False, default='', allow_blank=True, help_text='备注')
    external_id = serializers.CharField(max_length=120, help_text='外部订单号（必填）')
    external_finished_products = serializers.ListField(
        child=ExternalFinishedProductInputSerializer(),
        required=True,
        help_text='外部成品表结构数组（必填）'
    )

    def validate_external_id(self, value):
        value = (value or '').strip()
        if not value:
            raise serializers.ValidationError('external_id 不能为空')
        return value

    def validate_external_finished_products(self, value):
        if not value:
            raise serializers.ValidationError('external_finished_products 不能为空')
        return value


class SalesItemSerializer(serializers.Serializer):
    """
    销售品序列化器（只读）
    
    用于返回销售品数据
    """
    id = serializers.IntegerField(read_only=True)
    name = serializers.CharField(read_only=True)
    quantity = serializers.DecimalField(max_digits=12, decimal_places=2, read_only=True)
    unit = serializers.IntegerField(read_only=True)
    unit_display = serializers.SerializerMethodField()
    position = serializers.CharField(read_only=True)
    remark = serializers.CharField(read_only=True)
    printing_job_id = serializers.IntegerField(read_only=True)
    customer_id = serializers.IntegerField(read_only=True)
    shipment_id = serializers.IntegerField(source='shipment.id', read_only=True, allow_null=True)
    shipment_date = serializers.DateField(source='shipment.shipment_date', read_only=True, allow_null=True)
    created_at = serializers.DateTimeField(read_only=True)
    created_by_id = serializers.IntegerField(source='created_by.id', read_only=True, allow_null=True)
    created_by_name = serializers.SerializerMethodField()
    
    def get_unit_display(self, obj):
        return obj.get_unit_display()
    
    def get_created_by_name(self, obj):
        if obj.created_by:
            employee = getattr(obj.created_by, 'employee', None)
            if employee:
                return employee.name
            return obj.created_by.username
        return None