feat(comments): add basic OpenMetrics exporter

Signed-off-by: Benjamin Gaussorgues <benjamin.gaussorgues@nextcloud.com>

apps/comments/appinfo/info.xml

@@ -38,6 +38,10 @@
 		</providers>
 	</activity>
 
+	<openmetrics>
+		<exporter>OCA\Comments\OpenMetrics\CommentsCountMetric</exporter>
+	</openmetrics>
+
 	<collaboration>
 		<plugins>
 			<plugin type="autocomplete-sort">OCA\Comments\Collaboration\CommentersSorter</plugin>

apps/comments/composer/composer/autoload_classmap.php

@@ -22,5 +22,6 @@ return array(
     'OCA\\Comments\\MaxAutoCompleteResultsInitialState' => $baseDir . '/../lib/MaxAutoCompleteResultsInitialState.php',
     'OCA\\Comments\\Notification\\Listener' => $baseDir . '/../lib/Notification/Listener.php',
     'OCA\\Comments\\Notification\\Notifier' => $baseDir . '/../lib/Notification/Notifier.php',
+    'OCA\\Comments\\OpenMetrics\\CommentsCountMetric' => $baseDir . '/../lib/OpenMetrics/CommentsCountMetric.php',
     'OCA\\Comments\\Search\\CommentsSearchProvider' => $baseDir . '/../lib/Search/CommentsSearchProvider.php',
 );

apps/comments/composer/composer/autoload_static.php

@@ -37,6 +37,7 @@ class ComposerStaticInitComments
         'OCA\\Comments\\MaxAutoCompleteResultsInitialState' => __DIR__ . '/..' . '/../lib/MaxAutoCompleteResultsInitialState.php',
         'OCA\\Comments\\Notification\\Listener' => __DIR__ . '/..' . '/../lib/Notification/Listener.php',
         'OCA\\Comments\\Notification\\Notifier' => __DIR__ . '/..' . '/../lib/Notification/Notifier.php',
+        'OCA\\Comments\\OpenMetrics\\CommentsCountMetric' => __DIR__ . '/..' . '/../lib/OpenMetrics/CommentsCountMetric.php',
         'OCA\\Comments\\Search\\CommentsSearchProvider' => __DIR__ . '/..' . '/../lib/Search/CommentsSearchProvider.php',
     );
 

apps/comments/lib/OpenMetrics/CommentsCountMetric.php

@@ -0,0 +1,52 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OCA\Comments\OpenMetrics;
+
+use Generator;
+use OC\DB\Connection;
+use OCP\OpenMetrics\IMetricFamily;
+use OCP\OpenMetrics\Metric;
+use OCP\OpenMetrics\MetricType;
+use Override;
+
+class CommentsCountMetric implements IMetricFamily {
+	public function __construct(
+		private Connection $connection,
+	) {
+	}
+
+	#[Override]
+	public function name(): string {
+		return 'comments';
+	}
+
+	#[Override]
+	public function type(): MetricType {
+		return MetricType::gauge;
+	}
+
+	#[Override]
+	public function unit(): string {
+		return 'comments';
+	}
+
+	#[Override]
+	public function help(): string {
+		return 'Number of comments';
+	}
+
+	#[Override]
+	public function metrics(): Generator {
+		$qb = $this->connection->getQueryBuilder();
+		$result = $qb->select($qb->func()->count())
+			->from('comments')
+			->where($qb->expr()->eq('verb', $qb->expr()->literal('comment')))
+			->executeQuery();
+
+		yield new Metric($result->fetchOne(), [], time());
+	}
+}