Use controllers to redirect

app/controllers/projects/build_artifacts_controller.rb

+class Projects::BuildArtifactsController < Projects::ApplicationController
+  include ExtractsPath
+  include RendersBlob
+
+  before_action :extract_ref_name_and_path
+
+  def download
+    redirect_to download_namespace_project_job_artifacts_path(project.namespace, project, job)
+  end
+
+  def browse
+    redirect_to browse_namespace_project_job_artifacts_path(project.namespace, project, job, path: params[:path])
+  end
+
+  def file
+    redirect_to file_namespace_project_job_artifacts_path(project.namespace, project, job, path: params[:path])
+  end
+
+  def raw
+    redirect_to raw_namespace_project_job_artifacts_path(project.namespace, project, job, path: params[:path])
+  end
+
+  def latest_succeeded
+    redirect_to latest_succeeded_namespace_project_artifacts_path(project.namespace, project, job, ref_name_and_path: params[:ref_name_and_path], job: params[:job])
+  end
+
+  private
+
+  def extract_ref_name_and_path
+    return unless params[:ref_name_and_path]
+
+    @ref_name, @path = extract_ref(params[:ref_name_and_path])
+  end
+
+  def job
+    @job ||= job_from_id || job_from_ref
+  end
+
+  def job_from_id
+    project.builds.find_by(id: params[:build_id]) if params[:build_id]
+  end
+
+  def job_from_ref
+    return unless @ref_name
+
+    jobs = project.latest_successful_builds_for(@ref_name)
+    jobs.find_by(name: params[:job])
+  end
+end

app/controllers/projects/builds_controller.rb

+class Projects::BuildsController < Projects::ApplicationController
+  def index
+    redirect_to namespace_project_jobs_path(project.namespace, project)
+  end
+
+  def show
+    redirect_to namespace_project_job_path(project.namespace, project, job)
+  end
+
+  def trace
+    redirect_to trace_namespace_project_job_path(project.namespace, project, job, format: params[:format])
+  end
+
+  def status
+    redirect_to status_namespace_project_job_path(project.namespace, project, job, format: params[:format])
+  end
+
+  def raw
+    redirect_to raw_namespace_project_job_path(project.namespace, project, job)
+  end
+
+  private
+
+  def job
+    @job ||= project.builds.find(params[:id])
+  end
+end

lib/gitlab/routes/legacy_builds.rb

-
 module Gitlab
   module Routes
     class LegacyBuilds
@@ -10,51 +9,32 @@ module Gitlab
       end
 
       def draw
-        redirect_artifacts = @map.redirect(&method(:redirect_artifacts))
-        redirect_builds = @map.redirect(&method(:redirect_builds))
-
-        @map.get '/builds(/:id)/artifacts/*action', to: redirect_artifacts,
-                                                    as: 'legacy_artifacts',
-                                                    format: false
-
-        @map.get '/builds(/:id(/*action))', to: redirect_builds,
-                                            as: 'legacy_builds',
+        @map.instance_eval do
+          resources :builds, only: [:index, :show], constraints: { id: /\d+/ } do
+            collection do
+              resources :artifacts, only: [], controller: 'build_artifacts' do
+                collection do
+                  get :latest_succeeded,
+                    path: '*ref_name_and_path',
                     format: false
                 end
-
-      private
-
-      def redirect_artifacts(params, req)
-        if params[:id]
-          project = fake_project(*params.values_at(:namespace_id, :project_id))
-
-          artifacts_action_path(params[:action], project, params[:id])
-        else
-          latest_succeeded_namespace_project_artifacts_path(params[:namespace_id], params[:project_id], params[:action], job: req.GET[:job])
               end
             end
 
-      def redirect_builds(params, req)
-        args = params.values_at(:namespace_id, :project_id, :id).compact
+            member do
+              get :status
+              get :trace, defaults: { format: 'json' }
+              get :raw
+            end
 
-        if params[:id]
-          case params[:action]
-          when 'status'
-            status_namespace_project_job_path(*args, format: params[:format])
-          when 'trace'
-            trace_namespace_project_job_path(*args, format: params[:format])
-          when 'raw'
-            raw_namespace_project_job_path(*args)
-          else # show
-            namespace_project_job_path(*args)
+            resource :artifacts, only: [], controller: 'build_artifacts' do
+              get :download
+              get :browse, path: 'browse(/*path)', format: false
+              get :file, path: 'file/*path', format: false
+              get :raw, path: 'raw/*path', format: false
             end
-        else # index
-          namespace_project_jobs_path(*args)
           end
         end
-
-      def fake_project(namespace_id, project_id)
-        Struct.new(:namespace, :to_param).new(namespace_id, project_id)
       end
     end
   end