From 25aadd43106d5cec35370498e9796176829cc2b6 Mon Sep 17 00:00:00 2001
From: Tim Burt <tim@dorset-digital.net>
Date: Wed, 20 Jun 2018 17:14:22 +0100
Subject: [PATCH] Move extension to Page Add rules to YML to try and be last in
 line Add checking on existing tags to attempt to remove existing canonical
 tags

---
 _config/config.yml                 |  4 ++-
 src/SiteTreeCanonicalExtension.php | 52 +++++++++++++++++++-----------
 2 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/_config/config.yml b/_config/config.yml
index 0449647..07529c9 100644
--- a/_config/config.yml
+++ b/_config/config.yml
@@ -1,7 +1,9 @@
 ---
 Name: 'dd-canonical'
+After:
+  - '*'
 ---
-SilverStripe\CMS\Model\SiteTree:
+Page:
   extensions:
     - DorsetDigital\SilverStripeCanonical\SiteTreeCanonicalExtension
 
diff --git a/src/SiteTreeCanonicalExtension.php b/src/SiteTreeCanonicalExtension.php
index 0638672..6992692 100644
--- a/src/SiteTreeCanonicalExtension.php
+++ b/src/SiteTreeCanonicalExtension.php
@@ -8,23 +8,37 @@
 class SiteTreeCanonicalExtension extends SiteTreeExtension
 {
 
-    public function MetaTags(&$tags)
-    {
-
-        $siteConfig = SiteConfig::current_site_config();
-        if ($siteConfig->CanonicalDomain != '') {
-            $canonicalBase = trim($siteConfig->CanonicalDomain, '/');
-            if (method_exists($this->owner, 'CanonicalLink')) {
-                $link = $this->owner->CanonicalLink();
-            } else {
-                $link = $this->owner->Link();
-            }
-            $canonLink = $canonicalBase . $link;
-            $atts = [
-                'rel' => 'canonical',
-                'href' => $canonLink
-            ];
-            $tags .= "\n" . HTML::createTag('link', $atts) . "\n";
-        }
-    }
+ public function MetaTags(&$tags)
+ {
+
+  $siteConfig = SiteConfig::current_site_config();
+  if ($siteConfig->CanonicalDomain != '') {
+   $canonicalBase = trim($siteConfig->CanonicalDomain, '/');
+   if (method_exists($this->owner, 'CanonicalLink')) {
+    $link = $this->owner->CanonicalLink();
+   } else {
+    $link = $this->owner->Link();
+   }
+   $canonLink = $canonicalBase . $link;
+   $atts = [
+       'rel' => 'canonical',
+       'href' => $canonLink
+   ];
+   $canonTag = HTML::createTag('link', $atts);
+
+   $tagsArray = explode(PHP_EOL, $tags);
+   $tagPattern = 'rel="canonical"';
+
+   $tagSearch = function ( $val ) use ( $tagPattern ) {
+    return ( stripos($val, $tagPattern) !== false ? true : false );
+   };
+
+   $currentTags = array_filter($tagsArray, $tagSearch);
+   $cleanedTags = array_diff($tagsArray, $currentTags);
+
+   $cleanedTags[] = $canonTag;
+
+   $tags = implode(PHP_EOL, $cleanedTags);
+  }
+ }
 }