Prune local backups to retain the most recent two

ts/test-node/services/backups/localBackup_test.node.ts

@@ -0,0 +1,116 @@
+// Copyright 2026 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import path from 'node:path';
+import { tmpdir } from 'node:os';
+import { mkdir, mkdtemp, rm, readdir, writeFile } from 'node:fs/promises';
+import { exists } from 'fs-extra';
+
+import {
+  getLocalBackupFilesDirectory,
+  getLocalBackupPathForMediaName,
+  pruneLocalBackups,
+  writeLocalBackupFilesList,
+} from '../../../services/backups/util/localBackup.node.js';
+
+async function createSnapshot({
+  backupsBaseDir,
+  snapshotName,
+  mediaNames,
+}: {
+  backupsBaseDir: string;
+  snapshotName: string;
+  mediaNames: Array<string>;
+}): Promise<string> {
+  const snapshotDir = path.join(backupsBaseDir, snapshotName);
+  await mkdir(snapshotDir, { recursive: true });
+  await writeLocalBackupFilesList({ snapshotDir, mediaNames });
+
+  await Promise.all(
+    mediaNames.map(async mediaName => {
+      const mediaPath = getLocalBackupPathForMediaName({
+        backupsBaseDir,
+        mediaName,
+      });
+      await mkdir(path.dirname(mediaPath), { recursive: true });
+      await writeFile(mediaPath, mediaName);
+    })
+  );
+
+  return snapshotDir;
+}
+
+describe('localBackup/pruneLocalBackups', () => {
+  let backupsBaseDir: string;
+
+  beforeEach(async () => {
+    backupsBaseDir = await mkdtemp(
+      path.join(tmpdir(), 'signal-local-backup-prune-')
+    );
+  });
+
+  afterEach(async () => {
+    await rm(backupsBaseDir, { recursive: true, force: true });
+  });
+
+  async function listFiles() {
+    return (
+      await readdir(getLocalBackupFilesDirectory({ backupsBaseDir }), {
+        withFileTypes: true,
+        recursive: true,
+      })
+    )
+      .filter(entry => entry.isFile())
+      .map(entry => entry.name);
+  }
+
+  it('keeps two newest snapshots and deletes unreferenced media files', async () => {
+    const snapshotOld = await createSnapshot({
+      backupsBaseDir,
+      snapshotName: 'signal-backup-2026-03-08-12-00-01',
+      mediaNames: ['aa-old', 'dd-shared'],
+    });
+    const snapshotMiddle = await createSnapshot({
+      backupsBaseDir,
+      snapshotName: 'signal-backup-2026-03-08-12-00-02',
+      mediaNames: ['bb-middle', 'dd-shared'],
+    });
+    const snapshotNewest = await createSnapshot({
+      backupsBaseDir,
+      snapshotName: 'signal-backup-2026-03-08-12-00-03',
+      mediaNames: ['cc-newest', 'dd-shared'],
+    });
+
+    const orphanMediaPath = getLocalBackupPathForMediaName({
+      backupsBaseDir,
+      mediaName: 'ee-orphan',
+    });
+
+    await mkdir(path.dirname(orphanMediaPath), { recursive: true });
+    await writeFile(orphanMediaPath, 'orphan');
+
+    assert.sameDeepMembers(await listFiles(), [
+      'aa-old',
+      'bb-middle',
+      'cc-newest',
+      'dd-shared',
+      'ee-orphan',
+    ]);
+
+    await pruneLocalBackups({
+      backupsBaseDir,
+      numSnapshotsToKeep: 2,
+    });
+
+    assert.isTrue(await exists(snapshotNewest));
+    assert.isTrue(await exists(snapshotMiddle));
+    assert.isFalse(await exists(snapshotOld));
+
+    assert.sameDeepMembers(await listFiles(), [
+      'bb-middle',
+      'cc-newest',
+      'dd-shared',
+    ]);
+  });
+});