Implement API endpoint to query permissions.

app/controllers/api_controller.rb

@@ -2,6 +2,7 @@ class ApiController < ApplicationController
 
   skip_before_filter :verify_authenticity_token
   before_filter :check_api_readable, :except => [:capabilities]
+  before_filter :setup_user_auth, :only => [:permissions]
   after_filter :compress_output
   around_filter :api_call_handle_error, :api_call_timeout
 
@@ -289,4 +290,20 @@ class ApiController < ApplicationController
 
     render :text => doc.to_s, :content_type => "text/xml"
   end
+
+  # External apps that use the api are able to query which permissions
+  # they have. This currently returns a list of permissions granted to the current user:
+  # * if authenticated via OAuth, this list will contain all permissions granted by the user to the access_token.
+  # * if authenticated via basic auth all permissions are granted, so the list will contain all permissions.
+  # * unauthenticated users have no permissions, so the list will be empty.
+  def permissions
+    @permissions = case
+                   when current_token.present?
+                     ClientApplication.all_permissions.select { |p| current_token.read_attribute(p) }
+                   when @user
+                     ClientApplication.all_permissions
+                   else
+                     []
+                   end
+  end
 end

app/views/api/permissions.builder

@@ -0,0 +1,9 @@
+# create list of permissions
+xml.instruct! :xml, :version=>"1.0"
+xml.osm("version" => "#{API_VERSION}", "generator" => "OpenStreetMap Server") do
+  xml.permissions do
+    @permissions.each do |permission|
+      xml.permission :name => permission
+    end
+  end
+end

config/routes.rb

@@ -2,6 +2,7 @@ OpenStreetMap::Application.routes.draw do
   # API
   match 'api/capabilities' => 'api#capabilities', :via => :get
   match 'api/0.6/capabilities' => 'api#capabilities', :via => :get
+  match 'api/0.6/permissions' => 'api#permissions', :via => :get
 
   match 'api/0.6/changeset/create' => 'changeset#create', :via => :put
   match 'api/0.6/changeset/:id/upload' => 'changeset#upload', :via => :post, :id => /\d+/

test/functional/api_controller_test.rb

@@ -298,4 +298,41 @@ class ApiControllerTest < ActionController::TestCase
       end
     end
   end
+
+  def test_permissions_anonymous
+    get :permissions
+    assert_response :success
+    assert_select "osm > permissions", :count => 1 do
+      assert_select "permission", :count => 0
+    end
+  end
+
+  def test_permissions_basic_auth
+    basic_authorization(users(:normal_user).email, "test")
+    get :permissions
+    assert_response :success
+    assert_select "osm > permissions", :count => 1 do
+      assert_select "permission", :count => ClientApplication.all_permissions.size
+      ClientApplication.all_permissions.each do |p|
+        assert_select "permission[name=#{p}]", :count => 1
+      end
+    end
+  end
+
+  def test_permissions_oauth
+    @request.env["oauth.token"] =  AccessToken.new do |token|
+      # Just to test a few
+      token.allow_read_prefs = true
+      token.allow_write_api = true
+      token.allow_read_gpx = false
+    end
+    get :permissions
+    assert_response :success
+    assert_select "osm > permissions", :count => 1 do
+      assert_select "permission", :count => 2
+      assert_select "permission[name=allow_read_prefs]", :count => 1
+      assert_select "permission[name=allow_write_api]", :count => 1
+      assert_select "permission[name=allow_read_gpx]", :count => 0
+    end
+  end
 end