from rest_framework import viewsets
from rest_framework.exceptions import PermissionDenied
from rest_framework.pagination import LimitOffsetPagination
from rest_framework.permissions import IsAuthenticated, DjangoModelPermissions
from django_filters.rest_framework import DjangoFilterBackend
from django_filters import rest_framework as dj_filters

from . import serializers


class BasicInfoFilterMixin:
    """
    提供基于 name/title 的基础过滤能力，自动判定字段，避免重复配置。
    """
    filter_backends = [DjangoFilterBackend]
    _auto_filterset_cache = {}

    def _detect_filter_field(self):
        """
        返回 field_name 或 None。
        """
        model = getattr(getattr(self, 'queryset', None), 'model', None)
        if model is None:
            try:
                qs = super().get_queryset()
                model = getattr(qs, 'model', None)
            except Exception:
                return None

        field_names = {f.name for f in model._meta.get_fields() if hasattr(f, 'name')}
        # 优先级：name > title > driver_name
        if 'name' in field_names:
            return 'name'
        if 'title' in field_names:
            return 'title'
        if 'driver_name' in field_names:
            return 'driver_name'
        return None

    def _build_filterset_class(self, model, field):
        """
        动态构建 FilterSet，参数名直接使用字段名，lookup 使用 icontains。
        """
        cache_key = (model, field)
        if cache_key in self._auto_filterset_cache:
            return self._auto_filterset_cache[cache_key]

        meta_cls = type(
            'Meta',
            (),
            {
                'model': model,
                'fields': [field],
            },
        )
        auto_filter_cls = type(
            f'{model.__name__}AutoFilter',
            (dj_filters.FilterSet,),
            {
                field: dj_filters.CharFilter(field_name=field, lookup_expr='icontains'),
                'Meta': meta_cls,
            },
        )

        self._auto_filterset_cache[cache_key] = auto_filter_cls
        return auto_filter_cls

    def filter_queryset(self, queryset):
        field = self._detect_filter_field()
        model = getattr(getattr(self, 'queryset', None), 'model', None)
        if not field or not model:
            return super().filter_queryset(queryset)

        self.filterset_class = self._build_filterset_class(model, field)
        return super().filter_queryset(queryset)


class BaseViewSet(BasicInfoFilterMixin, viewsets.ModelViewSet):
    pagination_class = LimitOffsetPagination

    def get_queryset(self):
        qs = super().get_queryset()
        # 如果是超级用户，返回所有数据
        # TODO: 测试结束后要取注释
        # if self.request.user.is_superuser:
        #     return qs
        return qs.filter(merchant=self.request.user.employee.merchant)

    def perform_create(self, serializer):
        try:
            merchant = self.request.user.employee.merchant
            serializer.save(merchant_id=merchant.id)
        except AttributeError:
            raise PermissionDenied("无权限创建该对象")


class QuickInputViewSet(BasicInfoFilterMixin, viewsets.ModelViewSet):
    queryset = serializers.basic_models.QuickInput.objects.all()
    serializer_class = serializers.QuickInputSerializer
    pagination_class = LimitOffsetPagination

    def filter_queryset(self, queryset):
        qs = super().filter_queryset(queryset)
        group = self.request.query_params.get('group')
        if group:
            qs = qs.filter(group=group)
        return qs


class ProductViewSet(BaseViewSet):
    queryset = serializers.basic_models.Product.objects
    serializer_class = serializers.ProductSerializer


class WareHouseViewSet(BaseViewSet):
    queryset = serializers.basic_models.WareHouse.objects
    serializer_class = serializers.WareHouseSerializer


class ProductCategoryViewSet(BaseViewSet):
    queryset = serializers.basic_models.ProductCategory.objects
    serializer_class = serializers.ProductCategorySerializer


class SupplierViewSet(BaseViewSet):
    queryset = serializers.basic_models.Supplier.objects
    serializer_class = serializers.SupplierSerializer


class EmployeeViewSet(BaseViewSet):
    queryset = serializers.basic_models.Employee.objects
    serializer_class = serializers.EmployeeSerializer


class EmployeeTypeViewSet(BaseViewSet):
    queryset = serializers.basic_models.EmployeeType.objects
    serializer_class = serializers.EmployeeTypeSerializer


class CustomerViewSet(BaseViewSet):
    queryset = serializers.basic_models.Customer.objects
    serializer_class = serializers.CustomerSerializer
    permission_classes = [IsAuthenticated, DjangoModelPermissions]

    def perform_create(self, serializer):
        merchant = self.request.user.employee.merchant
        employee = self.request.user.employee
        serializer.save(merchant=merchant, created_by=employee)

    def can_view_all(self) -> bool:
        return self.request.user.is_superuser or self.request.user.has_perm('basic_info.view_all_customers')

    def get_queryset(self):
        qs = super().get_queryset()
        # 应用可见性过滤
        from basic_info.services import CustomerVisibilityService
        if self.can_view_all():
            return qs.filter(merchant=self.request.user.employee.merchant)
        return CustomerVisibilityService.filter_customers_for_employee(qs, self.request.user)
    
    def has_permission(self, request, view):
        if request.user.is_superuser or request.user.has_perm('basic_info.view_all_customer'):
            return True
        return super().has_permission(request, view)


class VehicleTypeViewSet(BaseViewSet):
    queryset = serializers.basic_models.VehicleType.objects
    serializer_class = serializers.VehicleTypeSerializer


class BankAccountViewSet(BaseViewSet):
    queryset = serializers.basic_models.BankAccount.objects
    serializer_class = serializers.BankAccountSerializer


class DeviceInfoViewSet(BaseViewSet):
    queryset = serializers.basic_models.DeviceInfo.objects
    serializer_class = serializers.DeviceInfoSerializer


class VehicleTransportRecordViewSet(BaseViewSet):
    queryset = serializers.basic_models.VehicleTransportRecord.objects
    serializer_class = serializers.VehicleTransportRecordSerializer


class UserProfileViewSet(BaseViewSet):
    queryset = serializers.basic_models.UserProfile.objects
    serializer_class = serializers.UserProfileSerializer

    def filter_queryset(self, queryset):
        try:
            merchant = self.request.user.employee.merchant
            return super().filter_queryset(queryset).filter(merchant=merchant)
        except AttributeError:
            raise PermissionDenied("无权限访问该对象")