new: [Dashboard] Adding user count evolution widget

app/Lib/Dashboard/UsersEvolutionWidget.php

@@ -0,0 +1,82 @@
+<?php
+
+
+class UsersEvolutionWidget
+{
+    public $title = 'Evolution of user count';
+    public $render = 'MultiLineChart';
+    public $width = 7;
+    public $height = 6;
+    public $description = 'A graph to show the evolution of total users over time';
+    public $cacheLifetime = 10;
+    public $autoRefreshDelay = false;
+    public $params = array(
+        'days' => 'Number of days to consider for the graph, takes priority over months and weeks. There will be a data entry for each day. Value between 1 and 180.',
+        'weeks' => 'Number of days to consider for the graph, takes priority over months. There will be a data entry for each week. Value between 1 and 180.',
+        'months' => 'Number of days to consider for the graph. There will be a data entry for each month. Value between 1 and 180.',
+    );
+
+    public $placeholder =
+        '{
+    "days": "30"
+}';
+
+    public function handler($user, $options = array())
+    {
+        $this->User = ClassRegistry::init('User');
+
+        $currentTime = strtotime("now");
+        $endOfDay = strtotime("tomorrow", $currentTime) - 1;
+        if (!empty($options['days'])) {
+            $limit = (int)($options['days']);
+            $delta = 'day';
+        } else if (!empty($options['weeks'])) {
+            $limit = (int)($options['weeks']);
+            $delta = 'week';
+        } else if (!empty($options['months'])) {
+            $limit = (int)($options['months']);
+            $delta = 'month';
+        } else {
+            $limit = 30;
+            $delta = 'day';
+        }
+
+        if ($limit <= 0 || $limit > 180) {
+            throw new InvalidArgumentException("Number of days, weeks or months must be a number between 1 and 180.");
+        }
+
+        $data = array();
+        $data['data'] = array();
+        // Add total users data for all timestamps
+        for ($i = 0; $i < $limit; $i++) {
+            $itemTime = strtotime('- ' . $i . $delta, $endOfDay);
+            $item = array();
+            $item['date'] = strftime('%Y-%m-%d', $itemTime);
+            $item['users'] = $this->usersAtTime($itemTime);
+            $data['data'][] = $item;
+        }
+
+        return $data;
+    }
+
+    private function usersAtTime($time)
+    {
+        return $this->User->find('count', array(
+            'recursive' => -1,
+            'conditions' => array(
+                'OR' => array(
+                    array('date_created' => null),
+                    array('date_created <=' => $time),
+                )
+            )
+        ));
+    }
+
+    public function checkPermissions($user)
+    {
+        if (empty($user['Role']['perm_site_admin'])) {
+            return false;
+        }
+        return true;
+    }
+}