[FEATURE] There's now validation for vanity mappings.

README.md

@@ -1,6 +1,6 @@
 # [misdirection](https://packagist.org/packages/nglasl/silverstripe-misdirection)
 
-_The current release is **3.0.0**_
+_The current release is **3.1.0**_
 
 > This module allows both simple and regular expression link redirections based on customisable mappings, either hooking into a page not found or replacing the default automated URL handling.
 

composer.json

@@ -37,7 +37,7 @@
 	},
 	"extra": {
 		"branch-alias": {
-			"dev-master": "3.0.x-dev"
+			"dev-master": "3.1.x-dev"
 		},
 		"expose": [
 			"client"

src/extensions/SiteTreeMisdirectionExtension.php

@@ -2,13 +2,15 @@
 
 namespace nglasl\misdirection;
 
+use SilverStripe\CMS\Controllers\CMSPageSettingsController;
 use SilverStripe\CMS\Model\SiteTree;
 use SilverStripe\Control\Controller;
 use SilverStripe\Control\Director;
 use SilverStripe\Core\Config\Config;
 use SilverStripe\Forms\HeaderField;
 use SilverStripe\Forms\TextField;
 use SilverStripe\ORM\DataExtension;
+use SilverStripe\ORM\ValidationResult;
 
 /**
  *	This extension provides vanity mapping directly from a page, and automatically creates the appropriate link mappings when replacing the default automated URL handling.
@@ -25,10 +27,6 @@ class SiteTreeMisdirectionExtension extends DataExtension {
 		'VanityMapping' => LinkMapping::class
 	);
 
-	/**
-	 *	Display the vanity mapping fields.
-	 */
-
 	public function updateSettingsFields($fields) {
 
 		$fields->addFieldToTab('Root.Misdirection', HeaderField::create(
@@ -52,6 +50,33 @@ public function updateSettingsFields($fields) {
 		$this->owner->extend('updateSiteTreeMisdirectionExtensionSettingsFields', $fields);
 	}
 
+	public function validate(ValidationResult $result) {
+
+		// Retrieve the vanity mapping URL, where this is only possible using the POST variable.
+
+		$vanityURL = (!Controller::has_curr() || is_null($controller = Controller::curr()) || is_null($URL = $controller->getRequest()->postVar('VanityURL'))) ? $this->owner->VanityMapping()->MappedLink : $URL;
+
+		// Determine whether another vanity mapping already exists.
+
+		$existing = LinkMapping::get()->filter(array(
+			'MappedLink' => $vanityURL,
+			'RedirectType' => 'Page',
+			'RedirectPageID:not' => array(
+				0,
+				$this->owner->ID
+			)
+		))->first();
+		if($result->isValid() && $existing && ($page = $existing->getRedirectPage())) {
+			$link = Controller::join_links(CMSPageSettingsController::singleton()->Link('show'), $page->ID);
+			$result->addError("Vanity URL <a href='{$link}' target='_blank'>already exists</a>!", ValidationResult::TYPE_ERROR, null, ValidationResult::CAST_HTML);
+		}
+
+		// Allow extension.
+
+		$this->owner->extend('validateSiteTreeMisdirectionExtension', $result);
+		return $result;
+	}
+
 	/**
 	 *	Update the corresponding vanity mapping.
 	 */

src/objects/LinkMapping.php

@@ -262,10 +262,6 @@ public function getCMSFields() {
 		return $fields;
 	}
 
-	/**
-	 *	Confirm that the current link mapping is valid.
-	 */
-
 	public function validate() {
 
 		$result = parent::validate();