Convert IndexedDB code to TypeScript

ts/indexeddb.ts

@@ -0,0 +1,52 @@
+// Copyright 2018-2022 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+const LEGACY_DATABASE_ID = 'signal';
+
+export async function doesDatabaseExist(): Promise<boolean> {
+  window.SignalContext.log.info(
+    'Checking for the existence of IndexedDB data...'
+  );
+  return new Promise((resolve, reject) => {
+    const req = window.indexedDB.open(LEGACY_DATABASE_ID);
+
+    let existed = true;
+
+    let timer: undefined | ReturnType<typeof setTimeout> = setTimeout(() => {
+      window.SignalContext.log.warn(
+        'doesDatabaseExist: Timed out attempting to check IndexedDB status'
+      );
+      return resolve(false);
+    }, 1000);
+
+    const clearTimer = () => {
+      if (timer !== undefined) {
+        clearTimeout(timer);
+        timer = undefined;
+      }
+    };
+
+    req.onerror = error => {
+      clearTimer();
+      reject(error);
+    };
+    req.onsuccess = () => {
+      clearTimer();
+      req.result.close();
+      resolve(existed);
+    };
+    req.onupgradeneeded = () => {
+      if (req.result.version === 1) {
+        existed = false;
+        window.indexedDB.deleteDatabase(LEGACY_DATABASE_ID);
+      }
+    };
+  });
+}
+
+export function removeDatabase(): void {
+  window.SignalContext.log.info(
+    `Deleting IndexedDB database '${LEGACY_DATABASE_ID}'`
+  );
+  window.indexedDB.deleteDatabase(LEGACY_DATABASE_ID);
+}