# Django 4.2.11 documentation

# Source code for django.views.decorators.http

    """
    Decorators for views based on HTTP headers.
    """
    import datetime
    from functools import wraps

    from django.http import HttpResponseNotAllowed
    from django.middleware.http import ConditionalGetMiddleware
    from django.utils import timezone
    from django.utils.cache import get_conditional_response
    from django.utils.decorators import decorator_from_middleware
    from django.utils.http import http_date, quote_etag
    from django.utils.log import log_response

    conditional_page = decorator_from_middleware(ConditionalGetMiddleware)

    def require_http_methods(request_method_list):
        """
        Decorator to make a view only accept particular request methods.  Usage::

            @require_http_methods(["GET", "POST"])
            def my_view(request):
                # I can assume now that only GET or POST requests make it this far
                # ...

        Note that request methods should be in uppercase.
        """

        def decorator(func):
            @wraps(func)
            def inner(request, *args, **kwargs):
                if request.method not in request_method_list:
                    response = HttpResponseNotAllowed(request_method_list)
                    log_response(
                        "Method Not Allowed (%s): %s",
                        request.method,
                        request.path,
                        response=response,
                        request=request,
                    )
                    return response
                return func(request, *args, **kwargs)

            return inner

        return decorator

    require_GET = require_http_methods(["GET"])
    require_GET.__doc__ = "Decorator to require that a view only accepts the GET method."

    require_POST = require_http_methods(["POST"])
    require_POST.__doc__ = "Decorator to require that a view only accepts the POST method."

    require_safe = require_http_methods(["GET", "HEAD"])
    require_safe.__doc__ = (
        "Decorator to require that a view only accepts safe methods: GET and HEAD."
    )

    def condition(etag_func=None, last_modified_func=None):
        """
        Decorator to support conditional retrieval (or change) for a view
        function.

        The parameters are callables to compute the ETag and last modified time for
        the requested resource, respectively. The callables are passed the same
        parameters as the view itself. The ETag function should return a string (or
        None if the resource doesn't exist), while the last_modified function
        should return a datetime object (or None if the resource doesn't exist).

        The ETag function should return a complete ETag, including quotes (e.g.
        '"etag"'), since that's the only way to distinguish between weak and strong
        ETags. If an unquoted ETag is returned (e.g. 'etag'), it will be converted
        to a strong ETag by adding quotes.

        This decorator will either pass control to the wrapped view function or
        return an HTTP 304 response (unmodified) or 412 response (precondition
        failed), depending upon the request method. In either case, the decorator
        will add the generated ETag and Last-Modified headers to the response if
        the headers aren't already set and if the request's method is safe.
        """

        def decorator(func):
            @wraps(func)
            def inner(request, *args, **kwargs):
                # Compute values (if any) for the requested resource.
                def get_last_modified():
                    if last_modified_func:
                        dt = last_modified_func(request, *args, **kwargs)
                        if dt:
                            if not timezone.is_aware(dt):
                                dt = timezone.make_aware(dt, datetime.timezone.utc)
                            return int(dt.timestamp())

                # The value from etag_func() could be quoted or unquoted.
                res_etag = etag_func(request, *args, **kwargs) if etag_func else None
                res_etag = quote_etag(res_etag) if res_etag is not None else None
                res_last_modified = get_last_modified()

                response = get_conditional_response(
                    request,
                    etag=res_etag,
                    last_modified=res_last_modified,
                )

                if response is None:
                    response = func(request, *args, **kwargs)

                # Set relevant headers on the response if they don't already exist
                # and if the request method is safe.
                if request.method in ("GET", "HEAD"):
                    if res_last_modified and not response.has_header("Last-Modified"):
                        response.headers["Last-Modified"] = http_date(res_last_modified)
                    if res_etag:
                        response.headers.setdefault("ETag", res_etag)

                return response

            return inner

        return decorator

    # Shortcut decorators for common cases based on ETag or Last-Modified only

    def etag(etag_func):
        return condition(etag_func=etag_func)

    def last_modified(last_modified_func):
        return condition(last_modified_func=last_modified_func)