Add children() method to Newsletter model to get child newsletters (history in case of post notif)

- added conditional display of "view history" link in Notification listing
- fixed indentation in duplicatePostNotif method according to code sniffer report

assets/js/src/newsletters/listings/notification.jsx

@@ -252,6 +252,20 @@ const NewsletterListNotification = React.createClass({
       </span>
     );
   },
+  renderHistoryLink: function(newsletter) {
+    const childrenCount = ~~(newsletter.children_count);
+    if (childrenCount === 0) {
+      return (
+        MailPoet.I18n.t('notSentYet')
+      );
+    } else {
+      return (
+        <Link
+          to={ `/notification/history/${ newsletter.id }` }
+        >{ MailPoet.I18n.t('viewHistory') }</Link>
+      );
+    }
+  },
   renderItem: function(newsletter, actions) {
     const rowClasses = classNames(
       'manage-column',
@@ -277,9 +291,7 @@ const NewsletterListNotification = React.createClass({
           { this.renderSettings(newsletter) }
         </td>
         <td className="column" data-colname={ MailPoet.I18n.t('history') }>
-          <Link
-            to={ `/notification/history/${ newsletter.id }` }
-          >{ MailPoet.I18n.t('viewHistory') }</Link>
+          { this.renderHistoryLink(newsletter) }
         </td>
         <td className="column-date" data-colname={ MailPoet.I18n.t('lastModifiedOn') }>
           <abbr>{ MailPoet.Date.format(newsletter.updated_at) }</abbr>

lib/Models/Newsletter.php

@@ -123,7 +123,8 @@ class Newsletter extends Model {
         'parent_id' => $this->id,
         'type' => self::TYPE_NOTIFICATION_HISTORY,
         'status' => self::STATUS_SENDING
-    ));
+      )
+    );
 
     $notification_history = self::create();
     $notification_history->hydrate($data);
@@ -163,6 +164,14 @@ class Newsletter extends Model {
     return parent::delete();
   }
 
+  function children() {
+    return $this->has_many(
+      __NAMESPACE__.'\Newsletter',
+      'parent_id',
+      'id'
+    );
+  }
+
   function segments() {
     return $this->has_many_through(
       __NAMESPACE__.'\Segment',
@@ -177,6 +186,11 @@ class Newsletter extends Model {
     return $this;
   }
 
+  function withChildrenCount() {
+    $this->children_count = $this->children()->count();
+    return $this;
+  }
+
   function options() {
     return $this->has_many_through(
       __NAMESPACE__.'\NewsletterOptionField',

lib/Router/Newsletters.php

@@ -267,7 +267,8 @@ class Newsletters {
       } else if($newsletter->type === Newsletter::TYPE_NOTIFICATION) {
         $newsletter
           ->withOptions()
-          ->withSegments();
+          ->withSegments()
+          ->withChildrenCount();
       } else if($newsletter->type === Newsletter::TYPE_NOTIFICATION_HISTORY) {
         $newsletter
           ->withSegments()