Routers and URL Patterns

class BaseRouter:
    """
    Base class for all router implementations.
    """
    def __init__(self):
        self.registry = []  # List of registered viewsets
    
    def register(self, prefix, viewset, basename=None):
        """
        Register a viewset with the router.
        
        Args:
            prefix (str): URL prefix for the viewset
            viewset: ViewSet class to register
            basename (str): Base name for URL patterns
        """
    
    def get_urls(self):
        """
        Generate URL patterns for all registered viewsets.
        
        Returns:
            list: Django URL patterns
        """
    
    def get_api_root_view(self, api_urls=None):
        """
        Create API root view showing available endpoints.
        
        Args:
            api_urls: URL patterns to include in root
            
        Returns:
            APIView: Root view class
        """
    
    def get_default_basename(self, viewset):
        """
        Get default basename from viewset's queryset model.
        
        Args:
            viewset: ViewSet class
            
        Returns:
            str: Default basename
        """

class SimpleRouter(BaseRouter):
    """
    Simple router generating basic URL patterns.
    """
    routes = [  # URL pattern templates
        # List route: /prefix/
        Route(
            url=r'^{prefix}{trailing_slash}$',
            mapping={'get': 'list', 'post': 'create'},
            name='{basename}-list',
            detail=False,
            initkwargs={'suffix': 'List'}
        ),
        # Detail route: /prefix/{lookup}/
        Route(
            url=r'^{prefix}/{lookup}{trailing_slash}$',
            mapping={
                'get': 'retrieve',
                'put': 'update', 
                'patch': 'partial_update',
                'delete': 'destroy'
            },
            name='{basename}-detail',
            detail=True,
            initkwargs={'suffix': 'Instance'}
        ),
    ]
    
    def __init__(self, trailing_slash=True):
        """
        Args:
            trailing_slash (bool): Include trailing slash in URLs
        """
        self.trailing_slash = '/' if trailing_slash else ''
        super().__init__()

class DefaultRouter(SimpleRouter):
    """
    Default router with API root view and optional format suffixes.
    """
    include_root_view = True      # Include API root endpoint
    include_format_suffixes = True  # Include format suffixes (.json, .xml)
    root_view_name = 'api-root'   # Name for root view
    default_schema_renderers = None  # Schema renderers for root view
    
    def get_api_root_view(self, api_urls=None):
        """
        Create browsable API root view.
        
        Returns:
            APIRootView: Root view showing available endpoints
        """

Route = namedtuple('Route', [
    'url',          # URL pattern template
    'mapping',      # HTTP method to viewset action mapping
    'name',         # URL pattern name template
    'detail',       # Whether route is for detail views
    'initkwargs'    # Additional viewset initialization kwargs
])

DynamicRoute = namedtuple('DynamicRoute', [
    'url',          # URL pattern template  
    'name',         # URL pattern name template
    'detail',       # Whether route is for detail views
    'initkwargs'    # Additional viewset initialization kwargs
])

class APIRootView(APIView):
    """
    Default API root view providing links to registered endpoints.
    """
    _ignore_model_permissions = True
    schema = None  # Disable schema generation for root
    api_root_dict = None  # Dictionary of available endpoints
    
    def get(self, request, *args, **kwargs):
        """
        Return links to all available API endpoints.
        
        Returns:
            Response: Dictionary of endpoint names and URLs
        """

def format_suffix_patterns(urlpatterns, suffix_required=False, allowed=None):
    """
    Add format suffix patterns to existing URL patterns.
    
    Args:
        urlpatterns (list): Existing URL patterns
        suffix_required (bool): Whether format suffix is required
        allowed (list): List of allowed format suffixes
        
    Returns:
        list: URL patterns with format suffix support
    """

def apply_suffix_patterns(urlpatterns, suffix_pattern, suffix_required, allowed):
    """
    Apply suffix patterns to URL patterns.
    
    Args:
        urlpatterns (list): URL patterns to modify
        suffix_pattern (str): Suffix pattern template
        suffix_required (bool): Whether suffix is required
        allowed (list): Allowed suffix values
        
    Returns:
        list: Modified URL patterns
    """

# urls.py
from rest_framework.routers import DefaultRouter
from myapp.views import BookViewSet, AuthorViewSet

# Create router instance
router = DefaultRouter()

# Register viewsets
router.register(r'books', BookViewSet)
router.register(r'authors', AuthorViewSet)

# Include router URLs
urlpatterns = [
    path('admin/', admin.site.urls),
    path('api/', include(router.urls)),
    path('api-auth/', include('rest_framework.urls')),
]

# Generated URLs:
# /api/ (API root)
# /api/books/ (list/create books)
# /api/books/{id}/ (retrieve/update/delete book)
# /api/authors/ (list/create authors)
# /api/authors/{id}/ (retrieve/update/delete author)

from rest_framework.viewsets import ModelViewSet
from rest_framework.decorators import action
from rest_framework.response import Response

class BookViewSet(ModelViewSet):
    queryset = Book.objects.all()
    serializer_class = BookSerializer
    
    @action(detail=True, methods=['post'])
    def set_favorite(self, request, pk=None):
        """Mark book as favorite for current user."""
        book = self.get_object()
        # Custom logic here
        return Response({'status': 'favorite set'})
    
    @action(detail=False, methods=['get'])
    def recent(self, request):
        """Get recently published books."""
        recent_books = self.queryset.filter(
            publication_date__gte=timezone.now() - timedelta(days=30)
        )
        serializer = self.get_serializer(recent_books, many=True)
        return Response(serializer.data)
    
    @action(detail=True, methods=['get'], url_path='reviews')
    def book_reviews(self, request, pk=None):
        """Get reviews for specific book."""
        book = self.get_object()
        reviews = book.reviews.all()
        # Serialize and return reviews
        return Response(review_data)

# Register with custom basename
router.register(r'books', BookViewSet, basename='book')

# Generated URLs include custom actions:
# /api/books/{id}/set_favorite/ (POST)
# /api/books/recent/ (GET)
# /api/books/{id}/reviews/ (GET)

# Main router for primary resources
main_router = DefaultRouter()
main_router.register(r'books', BookViewSet)
main_router.register(r'authors', AuthorViewSet)

# Secondary router for admin resources
admin_router = SimpleRouter()
admin_router.register(r'users', UserViewSet)
admin_router.register(r'logs', LogViewSet)

# Combine routers
urlpatterns = [
    path('api/v1/', include(main_router.urls)),
    path('api/admin/', include(admin_router.urls)),
    # Manual URL patterns can be mixed in
    path('api/auth/', include('rest_framework.authtoken.urls')),
]

from rest_framework.routers import Route, DynamicRoute, SimpleRouter

class CustomRouter(SimpleRouter):
    """
    Custom router with additional route patterns.
    """
    routes = [
        # Standard list route
        Route(
            url=r'^{prefix}{trailing_slash}$',
            mapping={'get': 'list', 'post': 'create'},
            name='{basename}-list',
            detail=False,
            initkwargs={'suffix': 'List'}
        ),
        # Custom bulk route
        Route(
            url=r'^{prefix}/bulk{trailing_slash}$',
            mapping={'post': 'bulk_create', 'patch': 'bulk_update'},
            name='{basename}-bulk',
            detail=False,
            initkwargs={}
        ),
        # Standard detail route
        Route(
            url=r'^{prefix}/{lookup}{trailing_slash}$',
            mapping={
                'get': 'retrieve',
                'put': 'update',
                'patch': 'partial_update',
                'delete': 'destroy'
            },
            name='{basename}-detail',
            detail=True,
            initkwargs={'suffix': 'Instance'}
        ),
        # Dynamic routes for @action decorated methods
        DynamicRoute(
            url=r'^{prefix}/{lookup}/{url_path}{trailing_slash}$',
            name='{basename}-{url_name}',
            detail=True,
            initkwargs={}
        ),
        DynamicRoute(
            url=r'^{prefix}/{url_path}{trailing_slash}$',
            name='{basename}-{url_name}',
            detail=False,
            initkwargs={}
        ),
    ]

# Usage
custom_router = CustomRouter()
custom_router.register(r'books', BookViewSet)

# Now supports bulk operations:
# POST /api/books/bulk/ -> bulk_create
# PATCH /api/books/bulk/ -> bulk_update

from rest_framework.urlpatterns import format_suffix_patterns

# Manual URL patterns with format suffixes
urlpatterns = [
    path('books/', BookListView.as_view(), name='book-list'),
    path('books/<int:pk>/', BookDetailView.as_view(), name='book-detail'),
]

# Add format suffix support
urlpatterns = format_suffix_patterns(urlpatterns)

# Now supports:
# /books/ or /books.json or /books.xml
# /books/1/ or /books/1.json or /books/1.xml

# Custom allowed formats
urlpatterns = format_suffix_patterns(
    urlpatterns, 
    allowed=['json', 'xml', 'yaml']
)

# Required suffix
urlpatterns = format_suffix_patterns(
    urlpatterns,
    suffix_required=True  # Must include format suffix
)

# Simple router without API root
simple_router = SimpleRouter()
simple_router.register(r'books', BookViewSet)

# Default router without root view
no_root_router = DefaultRouter()
no_root_router.include_root_view = False
no_root_router.register(r'books', BookViewSet)

# Custom trailing slash behavior
no_slash_router = DefaultRouter(trailing_slash=False)
no_slash_router.register(r'books', BookViewSet)

# URLs without trailing slashes:
# /api/books (instead of /api/books/)
# /api/books/1 (instead of /api/books/1/)

# Print all generated URLs for debugging
router = DefaultRouter()
router.register(r'books', BookViewSet)
router.register(r'authors', AuthorViewSet)

# Get all URL patterns
url_patterns = router.urls

for pattern in url_patterns:
    print(f"Pattern: {pattern.pattern}")
    print(f"Name: {pattern.name}")
    print(f"Callback: {pattern.callback}")
    print("---")

def escape_curly_brackets(url_path):
    """
    Escape curly brackets in URL path for regex patterns.
    
    Args:
        url_path (str): URL path that may contain curly brackets
        
    Returns:
        str: Escaped URL path
    """

def flatten(list_of_lists):
    """
    Flatten nested lists into single list.
    
    Args:
        list_of_lists (list): Nested list structure
        
    Returns:
        list: Flattened list
    """

def format_suffix_patterns(urlpatterns, suffix_required=False, allowed=None):
    """
    Add format suffix patterns to URL patterns.
    
    Args:
        urlpatterns (list): List of URL patterns
        suffix_required (bool): Whether format suffix is required
        allowed (list): List of allowed format suffixes
        
    Returns:
        list: URL patterns with format suffix support
    """

def apply_suffix_patterns(urlpatterns, suffix_pattern, suffix_required, suffix_route=None):
    """
    Apply suffix patterns to URL pattern list recursively.
    Internal function used by format_suffix_patterns.
    
    Args:
        urlpatterns (list): URL patterns to process
        suffix_pattern (str): Suffix pattern regex
        suffix_required (bool): Whether suffix is required
        suffix_route (str): Optional route suffix
        
    Returns:
        list: Processed URL patterns
    """