Don't override previously-set Link headers

If any Links were provided in the header before api-pagination does its
stuff, don't override them. Extract any Links that already exist and
append pagination Links to the list.

Signed-off-by: David Celis <[email protected]>

Author: davidcelis

lib/api-pagination.rb

@@ -3,6 +3,8 @@
 module ApiPagination
   protected
     def paginate(scope)
+      links = (headers['Link'] || "").split(',').map(&:strip)
+
       scope = instance_variable_get(:"@#{scope}")
       url   = request.original_url.sub(/\?.*$/, '')
       pages = {}
@@ -17,9 +19,9 @@ def paginate(scope)
         pages[:next] = scope.current_page + 1
       end
 
-      links = pages.map do |k, v|
+      pages.each do |k, v|
         new_params = request.query_parameters.merge({ :page => v })
-        %(<#{url}?#{new_params.to_param}>; rel="#{k}")
+        links << %(<#{url}?#{new_params.to_param}>; rel="#{k}")
       end
 
       headers['Link'] = links.join(', ') unless links.empty?

spec/controllers/numbers_controller_spec.rb

@@ -24,6 +24,13 @@ class NumbersController < ActionController::Base
   def index
     page = params.fetch(:page, 1).to_i
     total = params.fetch(:count).to_i
+
+    if params[:with_headers]
+      query = request.query_parameters
+      query.delete(:with_headers)
+      headers['Link'] = %(<#{numbers_url}?#{query.to_param}>; rel="without") if params[:with_headers]
+    end
+
     @numbers = PaginatedSet.new(page, total)
     render json: @numbers
   end
@@ -34,7 +41,23 @@ def index
     context 'without enough items to give more than one page' do
       it 'should not paginate' do
         get :index, count: 20
-        response.headers.keys.should_not include("Link")
+        response.headers.keys.should_not include('Link')
+      end
+    end
+
+    context 'with existing Link headers' do
+      before(:each) do
+        get :index, count: 30, with_headers: true
+        @links = response.headers['Link'].split(', ')
+      end
+
+      it 'should keep existing Links' do
+        @links.should include('<http://test.host/numbers?count=30>; rel="without"')
+      end
+
+      it 'should contain pagination Links' do
+        @links.should include('<http://test.host/numbers?count=30&page=2>; rel="next"')
+        @links.should include('<http://test.host/numbers?count=30&page=2>; rel="last"')
       end
     end