৩. Django Guardian অবজেক্ট লেভেল পারমিশন

django-admin startproject permission_system
cd permission_system
python manage.py startapp documents

pip install djangorestframework django-guardian

# Installed apps
INSTALLED_APPS = [
    # Django default apps...
    'rest_framework',
    'guardian',
    'documents',  # Our app
]

# Authentication backends for Django Guardian
AUTHENTICATION_BACKENDS = (
    'django.contrib.auth.backends.ModelBackend',  # Default backend
    'guardian.backends.ObjectPermissionBackend',  # Guardian backend for object-level permissions
)

# Guardian settings
ANONYMOUS_USER_ID = -1

# documents/models.py
from django.db import models
from django.contrib.auth.models import User

class Company(models.Model):
    name = models.CharField(max_length=255)

    def __str__(self):
        return self.name

class Document(models.Model):
    name = models.CharField(max_length=255)
    content = models.TextField()
    company = models.ForeignKey(Company, on_delete=models.CASCADE)
    created_by = models.ForeignKey(User, on_delete=models.CASCADE)

    def __str__(self):
        return self.name

# documents/admin.py
from django.contrib import admin
from .models import Document, Company

admin.site.register(Document)
admin.site.register(Company)

python manage.py makemigrations
python manage.py migrate

# documents/serializers.py
from rest_framework import serializers
from .models import Document

class DocumentSerializer(serializers.ModelSerializer):
    class Meta:
        model = Document
        fields = '__all__'

# documents/views.py
from rest_framework import viewsets, status
from rest_framework.response import Response
from guardian.shortcuts import assign_perm, get_perms
from rest_framework.permissions import IsAuthenticated
from .models import Document
from .serializers import DocumentSerializer

class DocumentViewSet(viewsets.ModelViewSet):
    queryset = Document.objects.all()
    serializer_class = DocumentSerializer
    permission_classes = [IsAuthenticated]

    def perform_create(self, serializer):
        # নতুন ডকুমেন্ট তৈরি হলে ইউজারকে পারমিশন অ্যাসাইন করা হবে
        document = serializer.save(created_by=self.request.user)
        assign_perm('documents.view_document', self.request.user, document)
        assign_perm('documents.change_document', self.request.user, document)
        assign_perm('documents.delete_document', self.request.user, document)

    def list(self, request, *args, **kwargs):
        # ইউজারের পারমিশন চেক করা
        queryset = Document.objects.filter(company=request.user.profile.company)
        serializer = self.get_serializer(queryset, many=True)
        return Response(serializer.data)
    
    def update(self, request, *args, **kwargs):
        document = self.get_object()
        if 'change_document' not in get_perms(request.user, document):
            return Response({'detail': 'Permission Denied'}, status=status.HTTP_403_FORBIDDEN)
        return super().update(request, *args, **kwargs)
        
    def destroy(self, request, *args, **kwargs):
        document = self.get_object()
        # Check if the user has the permission to delete the document
        if 'delete_document' not in get_perms(request.user, document):
            return Response({'detail': 'Permission Denied'}, status=status.HTTP_403_FORBIDDEN)
        return super().destroy(request, *args, **kwargs)        

# documents/urls.py
from django.urls import path, include
from rest_framework.routers import DefaultRouter
from .views import DocumentViewSet

router = DefaultRouter()
router.register(r'documents', DocumentViewSet)

urlpatterns = [
    path('', include(router.urls)),
]