added links route for API interactions

app.rb

@@ -41,10 +41,29 @@ class App < Roda
       code = links.filter(:url => url).first[:code]
       @message ||= "Link exists"
       @new_link = 'http://' + request.env['HTTP_HOST'] + '/' + code
-      if 'application/json' == r.headers['CONTENT_TYPE']
-        return {url: url, code: code, link: @new_link}.to_json
-      end
       view :create   
     end
+    r.on "links" do
+      r.post do
+        if 'application/json' != r.headers['CONTENT_TYPE']
+          return {message: "Not a valid JSON request"}.to_json
+        end
+
+        url = r.params['url']
+        if url.nil? or url.empty? 
+          response.status = 400
+          return {message: "Please enter a valid URL"}
+        end
+
+        if links.filter(:url => url).first.nil?
+          code = SecureRandom.urlsafe_base64 4
+          links.insert(url: url, code: code) 
+        end
+
+        code = links.filter(:url => url).first[:code]
+        @new_link = 'http://' + request.env['HTTP_HOST'] + '/' + code
+        return {url: url, code: code, link: @new_link}.to_json
+      end
+    end
   end
 end