Mixpanel analytics [MAILPOET-686] (#940)

* Send analytics data to mixpanel

[MAILPOET-686]

lib/Analytics/Analytics.php

@@ -0,0 +1,51 @@
+<?php
+namespace MailPoet\Analytics;
+use Carbon\Carbon;
+use MailPoet\Models\Setting;
+
+if(!defined('ABSPATH')) exit;
+
+class Analytics {
+
+  const SETTINGS_LAST_SENT_KEY = "analytics_last_sent";
+  const SEND_AFTER_DAYS = 7;
+
+  /** @var Reporter */
+  private $reporter;
+
+  public function __construct(Reporter $reporter) {
+    $this->reporter = $reporter;
+  }
+
+  /** @return array */
+  function generateAnalytics() {
+    if($this->shouldSend()) {
+      $data = $this->reporter->getData();
+      $this->recordDataSent();
+      return $data;
+    }
+  }
+
+  /** @return boolean */
+  function isEnabled() {
+    $analytics_settings = Setting::getValue('analytics', array());
+    return ($analytics_settings["enabled"] === "1") || ($analytics_settings["enabled"] === "true");
+  }
+
+  private function shouldSend() {
+    if(!$this->isEnabled()) {
+      return false;
+    }
+    $lastSent = Setting::getValue(Analytics::SETTINGS_LAST_SENT_KEY);
+    if(!$lastSent) {
+      return true;
+    }
+    $lastSentCarbon = Carbon::createFromTimestamp(strtotime($lastSent))->addDays(Analytics::SEND_AFTER_DAYS);
+    return $lastSentCarbon->isPast();
+  }
+
+  private function recordDataSent() {
+    Setting::setValue(Analytics::SETTINGS_LAST_SENT_KEY, Carbon::now());
+  }
+
+}