From 0678b8a426553110e63dde3c75aaf719e74771e1 Mon Sep 17 00:00:00 2001
From: Nihad Abbasov <narkoz.2008@gmail.com>
Date: Tue, 29 Oct 2013 13:41:20 +0400
Subject: [PATCH] add 'Link' header for API response

---
 lib/api/helpers.rb               | 20 ++++++++++++++++++--
 spec/requests/api/issues_spec.rb |  6 ++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/lib/api/helpers.rb b/lib/api/helpers.rb
index edc662eaaab..227081d4c10 100644
--- a/lib/api/helpers.rb
+++ b/lib/api/helpers.rb
@@ -51,8 +51,12 @@ module API
       end
     end
 
-    def paginate(object)
-      object.page(params[:page]).per(params[:per_page].to_i)
+    def paginate(relation)
+      per_page  = params[:per_page].to_i
+      paginated = relation.page(params[:page]).per(per_page)
+      add_pagination_headers(paginated, per_page)
+
+      paginated
     end
 
     def authenticate!
@@ -129,6 +133,18 @@ module API
 
     private
 
+    def add_pagination_headers(paginated, per_page)
+      request_url = request.url.split('?').first
+
+      links = []
+      links << %(<#{request_url}?page=#{paginated.current_page - 1}&per_page=#{per_page}>; rel="prev") unless paginated.first_page?
+      links << %(<#{request_url}?page=#{paginated.current_page + 1}&per_page=#{per_page}>; rel="next") unless paginated.last_page?
+      links << %(<#{request_url}?page=1&per_page=#{per_page}>; rel="first")
+      links << %(<#{request_url}?page=#{paginated.total_pages}&per_page=#{per_page}>; rel="last")
+
+      header 'Link', links.join(', ')
+    end
+
     def abilities
       @abilities ||= begin
                        abilities = Six.new
diff --git a/spec/requests/api/issues_spec.rb b/spec/requests/api/issues_spec.rb
index c55025d72b5..505e9597e1b 100644
--- a/spec/requests/api/issues_spec.rb
+++ b/spec/requests/api/issues_spec.rb
@@ -25,6 +25,12 @@ describe API::API do
         json_response.should be_an Array
         json_response.first['title'].should == issue.title
       end
+
+      it "should add pagination headers" do
+        get api("/issues?per_page=3", user)
+        response.headers['Link'].should ==
+          '<http://www.example.com/api/v3/issues?page=1&per_page=3>; rel="first", <http://www.example.com/api/v3/issues?page=1&per_page=3>; rel="last"'
+      end
     end
   end