Add HTTP handler that redirects requests for Mojo apps

services/mojo_url_redirector/__mojo__.py

Index: services/mojo_url_redirector/__mojo__.py
diff --git a/services/mojo_url_redirector/__mojo__.py b/services/mojo_url_redirector/__mojo__.py
new file mode 100644
index 0000000000000000000000000000000000000000..c0b843dda3699d65df9a23b3b7f0bb4529a382d5
--- /dev/null
+++ b/services/mojo_url_redirector/__mojo__.py
@@ -0,0 +1,143 @@
+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Application that serves requests for Mojo apps and responds with redirects
+to the locations of the most recent versions of these apps."""
+
+import http_request_mojom
+import http_response_mojom
+import http_server_mojom
+import http_server_factory_mojom
+import os

[qsr, 2015/02/25 15:34:07]

Maybe move this in its own section.

[blundell, 2015/02/26 13:29:52]

Done.

+import net_address_mojom
+import network_service_mojom
+import service_provider_mojom
+import url_loader_mojom
+
+from mojo_application import application_delegate
+from mojo_application import application_impl
+from mojo_application import application_runner
+
+from mojo_bindings import promise
+import mojo_system
+from mojo_utils import data_pipe_utils
+

[qsr, 2015/02/25 15:34:07]

2 blank lines.

[blundell, 2015/02/26 13:29:52]

Done.

+class MojoUrlRedirector(http_server_mojom.HttpHandler):
+  def __init__(self, network_service):
+    self.network_service = network_service
+
+  def HandleRequest(self, request):
+    print "Handling request for", request.relative_url
+
+    # Parse the components of the request.
+    relative_url_components = request.relative_url.split("/")
+
+    # The request must have a component for the platform and for the app.
+    if len(relative_url_components) != 3:
+      response = http_response_mojom.HttpResponse()
+      response.status_code = 400

[qsr, 2015/02/25 15:34:07]

Why isn't this a 404

[blundell, 2015/02/26 13:29:53]

400 is "Bad Request": "The server cannot or will not process the request due to
something that is perceived to be a client error (e.g., malformed request
syntax, invalid request message framing, or deceptive request routing)."

+      return response
+
+    requested_platform = relative_url_components[1]
+    requested_app = relative_url_components[2]
+
+    print "Request is for", requested_app, "on", requested_platform
+    return self.FindAppLocation(requested_platform, requested_app)
+
+  def FindAppLocation(self, requested_platform, requested_app):
+    # Construct a URLRequest to fetch the app location file...
+    app_location_request = url_loader_mojom.UrlRequest()
+    mojo_services_url = "https://storage.googleapis.com/mojo/services"
+    app_name = os.path.splitext(requested_app)[0]

[qsr, 2015/02/25 15:34:07]

You can write this as:
app_name, _ = os.path.splitext(requested_app)

[blundell, 2015/02/26 13:29:53]

Done.

+    app_location_request.url = "%s/%s/%s_location" % (mojo_services_url,
+                                                      requested_platform,
+                                                      app_name)
+    app_location_request.auto_follow_redirects = True
+
+    # ...and start a URLLoader to fetch it.
+    url_loader_proxy, request = url_loader_mojom.UrlLoader.manager.NewRequest()
+    self.network_service.CreateUrlLoader(request)
+
+    # Pass the URLLoader proxy to the callback to ensure that the pipe doesn't
+    # get closed before the callback runs.
+    on_version_fetched = lambda response: self.OnFoundAppLocation(

[qsr, 2015/02/25 15:34:07]

You might want to use functools.partial instead. You would just need to have
response as the last argument.

[blundell, 2015/02/26 13:29:52]

Done.

+        response, requested_platform, requested_app, url_loader_proxy)
+
+    print "Calling URL Loader to start"
+    return url_loader_proxy.Start(app_location_request).Then(
+        onFullfilled=on_version_fetched)

[qsr, 2015/02/25 15:34:07]

Do you want to have an onRejected with some logging?

[blundell, 2015/02/26 13:29:52]

Done.

+
+  def OnFoundAppLocation(self, app_location_response, requested_platform,
+                         requested_app, url_loader_proxy):
+    print "Load completed"
+
+    response = http_response_mojom.HttpResponse()
+    response.status_code = 404

[qsr, 2015/02/25 15:34:07]

What about a function returning this, and calling it when returning the 404. I
think it will be clearer.

[blundell, 2015/02/26 13:29:52]

Done.

+
+    if app_location_response.error:
+      print "Error fetching app location:", app_location_response.error
+      return response
+
+    if app_location_response.status_code != 200:
+      print "Unexpected http status in response to fetch of app location:",
+      print app_location_response.status_code
+      return response
+
+    # Read out the location of the app.
+    status, app_location = data_pipe_utils.BlockingCopyFromDataPipeIntoString(
+        app_location_response.body, 30 * 10**6)
+    print status
+    print app_location
+    if status != mojo_system.RESULT_OK:
+      print "Error reading app location:", status
+      return response
+    print "App location is", app_location
+
+    return self.RedirectToApp(requested_platform, requested_app, app_location)
+
+  def RedirectToApp(self, requested_platform, requested_app, app_location):
+    response = http_response_mojom.HttpResponse()
+    print "Redirecting to", app_location
+    response.status_code = 302
+    custom_headers = {}
+    custom_headers["location"] = app_location
+    response.custom_headers = custom_headers
+    return response
+
+
+class MojoUrlRedirectorApp(application_delegate.ApplicationDelegate):
+  def Initialize(self, shell, application):
+    server_address = net_address_mojom.NetAddress()
+    server_address.family = net_address_mojom.NetAddressFamily.IPV4
+    server_address.ipv4 = net_address_mojom.NetAddressIPv4()
+    server_address.ipv4.addr = [0, 0, 0, 0]
+    server_address.ipv4.port = 80
+
+    # Parse args if given.
+    if len(application.args) > 1:
+      assert len(application.args) == 2
+      server_address_arg = application.args[1]
+      server_address_str, server_port_str = server_address_arg.split(":")
+      server_address.ipv4.addr = [int(n) for n in server_address_str.split(".")]
+      server_address.ipv4.port = int(server_port_str)
+
+    # Connect to HttpServer.
+    http_server_factory = application.ConnectToService("mojo:http_server",
+        http_server_factory_mojom.HttpServerFactory)
+    self.http_server, request = \
+        http_server_mojom.HttpServer.manager.NewRequest()
+    http_server_factory.CreateHttpServer(request, server_address)
+
+    # Connect to NetworkService.
+    self.network_service = application.ConnectToService("mojo:network_service",
+        network_service_mojom.NetworkService)
+
+    # Construct a MojoUrlRedirector and add that as a handler to the server.
+    self.app_request_handler = MojoUrlRedirector(self.network_service)
+    self.http_server.SetHandler("/.*", self.app_request_handler)
+
+
+def MojoMain(app_request_handle):
+  application_runner.RunMojoApplication(MojoUrlRedirectorApp(),
+                                        app_request_handle)