Perform redirects on El Proxito 404 handler

We are not prepared yet to check and perform the redirects on El
Proxito serve docs. So, we are moving it to the 404 handler for now.

Once we want to activate it, we can just uncomment the lines on serve docs.

Author: humitos

readthedocs/proxito/views/mixins.py

@@ -1,9 +1,14 @@
 import logging
 import mimetypes
+from urllib.parse import urlparse, urlunparse
 
 from django.conf import settings
 from django.core.files.storage import get_storage_class
-from django.http import HttpResponse
+from django.http import (
+    HttpResponse,
+    HttpResponseRedirect,
+    HttpResponsePermanentRedirect,
+)
 from django.shortcuts import render
 from django.utils.encoding import iri_to_uri
 from django.views.static import serve
@@ -79,3 +84,47 @@ def _serve_401(self, request, project):
         res.status_code = 401
         log.debug('Unauthorized access to %s documentation', project.slug)
         return res
+
+
+class ServeRedirectMixin:
+
+    def get_redirect(self, project, lang_slug, version_slug, filename, full_path):
+        """
+        Check for a redirect for this project that matches ``full_path``.
+
+        :returns: the path to redirect the request and its status code
+        :rtype: tuple
+        """
+        redirect_path, http_status = project.redirects.get_redirect_path_with_status(
+            language=lang_slug,
+            version_slug=version_slug,
+            path=filename,
+            full_path=full_path,
+        )
+        return redirect_path, http_status
+
+    def get_redirect_response(self, request, redirect_path, http_status):
+        """
+        Build the response for the ``redirect_path`` and its ``http_status``.
+
+        :returns: redirect respose with the correct path
+        :rtype: HttpResponseRedirect or HttpResponsePermanentRedirect
+        """
+        schema, netloc, path, params, query, fragments = urlparse(request.path)
+        new_path = urlunparse((schema, netloc, redirect_path, params, query, fragments))
+
+        # Re-use the domain and protocol used in the current request.
+        # Redirects shouldn't change the domain, version or language.
+        # However, if the new_path is already an absolute URI, just use it
+        new_path = request.build_absolute_uri(new_path)
+        log.info(
+            'Redirecting: from=%s to=%s http_status=%s',
+            request.build_absolute_uri(),
+            new_path,
+            http_status,
+        )
+
+        if http_status and http_status == 301:
+            return HttpResponsePermanentRedirect(new_path)
+
+        return HttpResponseRedirect(new_path)

readthedocs/proxito/views/serve.py

@@ -3,11 +3,11 @@
 import itertools
 import logging
 import os
-from urllib.parse import urlparse, urlunparse
+from urllib.parse import urlparse
 
 from django.conf import settings
 from django.core.files.storage import get_storage_class
-from django.http import Http404, HttpResponse, HttpResponseRedirect, HttpResponsePermanentRedirect
+from django.http import Http404, HttpResponse, HttpResponseRedirect
 from django.shortcuts import render
 from django.urls import resolve as url_resolve
 from django.utils.decorators import method_decorator
@@ -20,7 +20,7 @@
 from readthedocs.projects import constants
 from readthedocs.projects.templatetags.projects_tags import sort_version_aware
 
-from .mixins import ServeDocsMixin
+from .mixins import ServeDocsMixin, ServeRedirectMixin
 
 from .decorators import map_project_slug
 from .redirects import redirect_project_slug
@@ -30,7 +30,7 @@
 log = logging.getLogger(__name__)  # noqa
 
 
-class ServeDocsBase(ServeDocsMixin, View):
+class ServeDocsBase(ServeRedirectMixin, ServeDocsMixin, View):
 
     def get(self,
             request,
@@ -77,29 +77,16 @@ def get(self,
             )
             raise Http404('Invalid URL for project with versions')
 
-        full_path = request.path
-        redirect_path, http_status = final_project.redirects.get_redirect_path_with_status(
-            language=lang_slug, version_slug=version_slug, path=filename, full_path=full_path,
-        )
-        if redirect_path is not None:
-            schema, netloc, path, params, query, fragments = urlparse(full_path)
-            new_path = urlunparse((schema, netloc, redirect_path, params, query, fragments))
-
-            # Re-use the domain and protocol used in the current request.
-            # Redirects shouldn't change the domain, version or language.
-            # However, if the new_path is already an absolute URI, just use it
-            new_path = request.build_absolute_uri(new_path)
-            log.info(
-                'Redirecting: from=%s to=%s http_status=%s',
-                request.build_absolute_uri(),
-                new_path,
-                http_status,
-            )
-
-            if http_status and http_status == 301:
-                return HttpResponsePermanentRedirect(new_path)
-
-            return HttpResponseRedirect(new_path)
+        # TODO: un-comment when ready to perform redirect here
+        # redirect_path, http_status = self.get_redirect(
+        #     final_project,
+        #     lang_slug,
+        #     version_slug,
+        #     filename,
+        #     request.path,
+        # )
+        # if redirect_path and http_status:
+        #     return self.get_redirect_response(request, redirect_path, http_status)
 
         # Check user permissions and return an unauthed response if needed
         if not self.allowed_user(request, final_project, version_slug):
@@ -125,7 +112,7 @@ class ServeDocs(SettingsOverrideObject):
     _default_class = ServeDocsBase
 
 
-class ServeError404Base(View):
+class ServeError404Base(ServeRedirectMixin, View):
 
     def get(self, request, proxito_path, template_name='404.html'):
         """
@@ -156,6 +143,17 @@ def get(self, request, proxito_path, template_name='404.html'):
             filename=kwargs.get('filename', ''),
         )
 
+        # Check and perform redirects on 404 handler
+        redirect_path, http_status = self.get_redirect(
+            final_project,
+            lang_slug,
+            version_slug,
+            filename,
+            request.path,
+        )
+        if redirect_path and http_status:
+            return self.get_redirect_response(request, redirect_path, http_status)
+
         storage_root_path = final_project.get_storage_path(
             type_='html',
             version_slug=version_slug,