from django.utils.decorators import decorator_from_middleware
from django.utils.deprecation import MiddlewareMixin

try:
    from django.core.urlresolvers import reverse
except ImportError:
    from django.urls import reverse


def add_webmention_headers_to_response(request, response):
    link_header = '<{scheme}://{host}{path}>; rel="webmention"'.format(
        scheme=request.scheme, host=request.META.get("HTTP_HOST"), path=reverse("webmention:receive")
    )
    if not response.get("Link"):
        response["Link"] = link_header
    else:
        response["Link"] = ", ".join((response["Link"], link_header))

    return response


class WebMentionMiddleware(MiddlewareMixin):
    def process_response(self, request, response):
        return add_webmention_headers_to_response(request, response)


def webmention_middleware(get_response):
    def middleware(request):
        response = get_response(request)
        return add_webmention_headers_to_response(request, response)

    return middleware


include_webmention_information = decorator_from_middleware(WebMentionMiddleware)