Add email notification to all users on server domain pattern block list update

src/Moderation/DomainPatternBlocklist.php

@@ -22,6 +22,7 @@
 namespace Friendica\Moderation;
 
 use Exception;
+use Friendica\App\BaseURL;
 use Friendica\Core\Config\Capability\IManageConfigValues;
 use Friendica\Core\L10n;
 use Friendica\Database\Database;
@@ -32,14 +33,28 @@ class DomainPatternBlocklist
 {
 	const DEFAULT_REASON = 'blocked';
 
-	/**
-	 * @var IManageConfigValues
-	 */
+	/** @var IManageConfigValues */
 	private $config;
 
-	public function __construct(IManageConfigValues $config)
+	/** @var Database */
+	private $db;
+
+	/** @var Emailer */
+	private $emailer;
+
+	/** @var L10n */
+	private $l10n;
+
+	/** @var BaseURL */
+	private $baseUrl;
+
+	public function __construct(IManageConfigValues $config, Database $db, Emailer $emailer, L10n $l10n, BaseURL $baseUrl)
 	{
 		$this->config  = $config;
+		$this->db      = $db;
+		$this->emailer = $emailer;
+		$this->l10n    = $l10n;
+		$this->baseUrl = $baseUrl;
 	}
 
 	public function get(): array
@@ -49,7 +64,12 @@ class DomainPatternBlocklist
 
 	public function set(array $blocklist): bool
 	{
-		return $this->config->set('system', 'blocklist', $blocklist);
+		$result = $this->config->set('system', 'blocklist', $blocklist);
+		if ($result) {
+			$this->notifyAll();
+		}
+
+		return $result;
 	}
 
 	/**
@@ -177,4 +197,50 @@ class DomainPatternBlocklist
 
 		return $blocklist;
 	}
+
+	/**
+	 * Sends a system email to all the node users about a change in the block list. Sends a single email to each unique
+	 * email address among the valid users.
+	 *
+	 * @return int The number of recipients that were sent an email
+	 * @throws HTTPException\InternalServerErrorException
+	 * @throws HTTPException\UnprocessableEntityException
+	 */
+	public function notifyAll(): int
+	{
+		// Gathering all non-system parent users who verified their email address and aren't blocked or about to be deleted
+		// We sort on language to minimize the number of actual language switches during the email build loop
+		$recipients = $this->db->selectToArray(
+			'user',
+			['username', 'email', 'language'],
+			['`uid` > 0 AND `parent-uid` = 0 AND `verified` AND NOT `account_removed` AND NOT `account_expired` AND NOT `blocked`'],
+			['group_by' => ['email'], 'order' => ['language']]
+		);
+		if (!$recipients) {
+			return 0;
+		}
+
+		foreach ($recipients as $recipient) {
+			$this->l10n->withLang($recipient['language']);
+			$email = $this->emailer->newSystemMail()
+				->withMessage(
+					$this->l10n->t('[%s] Notice of remote server domain pattern block list update', $this->emailer->getSiteEmailName()),
+					$this->l10n->t(
+						'Dear %s,
+
+You are receiving this email because the Friendica node at %s where you are registered as a user updated their remote server domain pattern block list.
+
+Please review the updated list at %s at your earliest convenience.',
+						$recipient['username'],
+						$this->baseUrl->get(),
+						$this->baseUrl . '/friendica'
+					)
+				)
+				->withRecipient($recipient['email'])
+				->build();
+			$this->emailer->send($email);
+		}
+
+		return count($recipients);
+	}
 }