FEATURE #1550: compute changefreq for entries in sitemap

app/Http/Controllers/Sitemap.php

@@ -24,7 +24,7 @@ class Sitemap extends Controller
 
     /**
      * Get sitemap for all content pages
-     * 
+     *
      * @return mixed
      */
     public function getMap()
@@ -33,10 +33,9 @@ class Sitemap extends Controller
         $pages = $this->content->getPageQuery()
                                ->get();
 
-
         // iterate over all pages and add tag for each of them
         foreach ($pages as $page) {
-            
+
             // is this page a homepage? because of URL
             if ($page->is_homepage) {
                 $route = route('page.index');
@@ -46,12 +45,54 @@ class Sitemap extends Controller
                 $priority = 0.8;
             }
 
-            // add to all pages
-            \Sitemap::addTag($route, $page->updated_at, 'daily', $priority);
+            // compute update frequency
+            $updateFrequency = $this->getUpdateFrequency($page->updated_at);
 
+            // add to all pages
+            \Sitemap::addTag($route, $page->updated_at, $updateFrequency, $priority);
         }
 
         // print sitemap
         return \Sitemap::render();
     }
+
+    /**
+     * Based on updatedAt compute "changefreq" for sitemap
+     *
+     * @param $updatedAt
+     */
+    private function getUpdateFrequency($updatedAt)
+    {
+        // shortcuts for times
+        $day = 24 * 60 * 60;
+        $week = 7 * $day;
+        $month = 4 * $week;
+        $year = 12 * $month;
+
+        // change frequencies in format "name" => maximum age of last editation
+        $changeFrequencies = [
+            'always'  => 300,
+            'hourly'  => 3600,
+            'daily'   => $day,
+            'weekly'  => $week,
+            'monthly' => $month,
+            'yearly'  => $year,
+            'never'   => PHP_INT_MAX,
+        ];
+
+        // get time difference
+        $timeDiffInMinutes = time() - strtotime($updatedAt);
+
+        // iterate over array with all change frequencies and break when time of edit is smaller than maximum time
+        do {
+            $changeFrequency = key($changeFrequencies);
+            $changeFreqMinTime = next($changeFrequencies);
+        } while ($timeDiffInMinutes > $changeFreqMinTime);
+
+        if ($changeFrequency != 'never') {
+            $changeFrequency = key($changeFrequencies);
+        }
+
+        return $changeFrequency;
+    }
 }