from django.contrib.auth import get_user_model
from django.contrib.auth.models import Group
from django.db import transaction
from rest_framework import serializers, status
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView

from basic_info import models as basic_models

User = get_user_model()


class RoleListView(APIView):
    """
    获取所有角色列表（基于 Django Group）。

    GET /api/v2/roles/
    返回: [{"id": 1, "name": "管理员"}, ...]
    """

    permission_classes = [IsAuthenticated]

    def get(self, request):
        roles = Group.objects.all().values('id', 'name').order_by('id')
        return Response(list(roles))


class QuickEmployeeUserCreateSerializer(serializers.Serializer):
    username = serializers.CharField(max_length=150)
    password = serializers.CharField(write_only=True, min_length=6)
    display_name = serializers.CharField(max_length=100)
    merchant_id = serializers.IntegerField()
    email = serializers.EmailField(required=False, allow_blank=True, allow_null=True)
    mobile = serializers.CharField(required=False, allow_blank=True, allow_null=True, max_length=20)
    area = serializers.CharField(required=False, allow_blank=True, allow_null=True, max_length=100)
    description = serializers.CharField(required=False, allow_blank=True, allow_null=True)
    status = serializers.ChoiceField(
        choices=basic_models.EmployeeStatusEnum.choices,
        required=False,
        default=basic_models.EmployeeStatusEnum.ACTIVE,
    )
    role_id = serializers.IntegerField(required=False, allow_null=True, help_text='角色ID（可选）')

    def validate_username(self, value):
        if User.objects.filter(username=value).exists():
            raise serializers.ValidationError('用户名已存在')
        return value

    def validate_merchant_id(self, value):
        if not basic_models.Merchant.objects.filter(id=value).exists():
            raise serializers.ValidationError('商户不存在')
        return value

    def validate_role_id(self, value):
        if value is not None and not Group.objects.filter(id=value).exists():
            raise serializers.ValidationError('角色不存在')
        return value


class QuickCreateEmployeeUserView(APIView):
    """
    快速创建系统用户 + 关联员工。

    POST /api/v2/users/quick-create/
    """

    permission_classes = [IsAuthenticated]

    def post(self, request):
        serializer = QuickEmployeeUserCreateSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        data = serializer.validated_data

        merchant = basic_models.Merchant.objects.get(id=data['merchant_id'])
        display_name = data['display_name']
        status_value = data.get('status') or basic_models.EmployeeStatusEnum.ACTIVE
        role_id = data.get('role_id')

        with transaction.atomic():
            user = User.objects.create_user(
                username=data['username'],
                password=data['password'],
                email=data.get('email') or '',
            )
            user.first_name = display_name
            user.save(update_fields=['first_name'])

            # 如果指定了角色，将用户添加到对应的 Group
            if role_id:
                group = Group.objects.get(id=role_id)
                user.groups.add(group)

            employee = basic_models.Employee.objects.create(
                merchant=merchant,
                sys_user=user,
                name=display_name,
                mobile=data.get('mobile') or '',
                area=data.get('area') or '',
                description=data.get('description') or '',
                status=status_value,
            )

        return Response(
            {
                'user': {
                    'id': user.id,
                    'username': user.username,
                    'display_name': display_name,
                    'role_id': role_id,
                },
                'employee': {
                    'id': employee.id,
                    'name': employee.name,
                    'status': employee.status,
                    'merchant': merchant.id,
                },
            },
            status=status.HTTP_201_CREATED,
        )