Add support to get size for image_cache

lib/platform/web/indexed_db.dart

@@ -0,0 +1,205 @@
+import 'dart:async';
+import 'dart:js_interop';
+import 'package:web/web.dart';
+
+Future<bool> makeStoragePersist() async {
+  final storage = window.navigator.storage;
+  bool peristed = (await storage.persisted().toDart).toDart;
+  if (!peristed) {
+    peristed = (await storage.persist().toDart).toDart;
+  }
+  return peristed;
+}
+
+class IndexedDb {
+  late IDBDatabase _db;
+  bool _inited = false;
+  bool get inited => _inited;
+  final String dbName;
+  final int? version;
+  final void Function(IDBVersionChangeEvent, IDBDatabase) onUpgradeNeeded;
+  IndexedDb(this.dbName, this.onUpgradeNeeded, this.version);
+  Future<JSAny?> _waitRequest(IDBRequest request) async {
+    bool ok = false;
+    bool handled = false;
+    void onsuccess(Event _) {
+      ok = true;
+      handled = true;
+    }
+
+    void onerror(Event _) {
+      handled = true;
+    }
+
+    request.onsuccess = onsuccess.toJS;
+    request.onerror = onerror.toJS;
+    FutureOr<bool> waitResult() {
+      if (handled) return ok;
+      return Future.delayed(const Duration(milliseconds: 1), waitResult);
+    }
+
+    await Future.microtask(waitResult);
+    if (ok) {
+      return request.result;
+    } else {
+      _inited = false;
+      throw request.error ?? "";
+    }
+  }
+
+  Future<void> init() async {
+    makeStoragePersist();
+    final req = version != null
+        ? window.indexedDB.open(dbName, version!)
+        : window.indexedDB.open(dbName);
+    void onupgradeneeded(IDBVersionChangeEvent event) {
+      onUpgradeNeeded(event, req.result as IDBDatabase);
+    }
+
+    req.onupgradeneeded = onupgradeneeded.toJS;
+    bool ok = false;
+    bool handled = false;
+    void onsuccess(Event _) {
+      ok = true;
+      handled = true;
+    }
+
+    void onerror(Event _) {
+      handled = true;
+    }
+
+    req.onsuccess = onsuccess.toJS;
+    req.onerror = onerror.toJS;
+    FutureOr<bool> waitResult() {
+      if (handled) return ok;
+      return Future.delayed(const Duration(milliseconds: 1), waitResult);
+    }
+
+    await Future.microtask(waitResult);
+    if (ok) {
+      _db = req.result as IDBDatabase;
+    } else {
+      throw req.error ?? "";
+    }
+    _inited = true;
+  }
+
+  Future<void> clear(String table) async {
+    final tx = _db.transaction([table.toJS].toJS, 'readwrite');
+    final store = tx.objectStore(table);
+    final req = store.clear();
+    await _waitRequest(req);
+  }
+
+  Future<void> delete(String table, JSAny key) async {
+    final tx = _db.transaction([table.toJS].toJS, 'readwrite');
+    final store = tx.objectStore(table);
+    final req = store.delete(key);
+    await _waitRequest(req);
+  }
+
+  Future<JSAny?> get(String table, JSAny key) async {
+    await init();
+    final tx = _db.transaction([table.toJS].toJS, 'readonly');
+    final store = tx.objectStore(table);
+    final req = store.get(key);
+    return await _waitRequest(req);
+  }
+
+  Future<JSArray<JSAny?>> getAllKeys(String table,
+      {JSAny? query, int? count}) async {
+    await init();
+    final tx = _db.transaction([table.toJS].toJS, 'readonly');
+    final store = tx.objectStore(table);
+    final req = query != null && count != null
+        ? store.getAllKeys(query, count!)
+        : query != null
+            ? store.getAllKeys(query)
+            : store.getAllKeys();
+    final r = await _waitRequest(req);
+    return r as JSArray<JSAny?>;
+  }
+
+  Future<void> openCursor(
+      String table, void Function(IDBCursorWithValue) callback,
+      {JSAny? query, String? direction, bool readwrite = false}) async {
+    await init();
+    final tx = _db.transaction(
+        [table.toJS].toJS, readwrite ? 'readwrite' : 'readonly');
+    final store = tx.objectStore(table);
+    final req = query != null && direction != null
+        ? store.openCursor(query, direction!)
+        : query != null
+            ? store.openCursor(query)
+            : store.openCursor();
+    bool ok = false;
+    bool handled = false;
+    void onsuccess(Event _) {
+      if (req.result != null) {
+        final cursor = req.result as IDBCursorWithValue;
+        callback(cursor);
+      } else {
+        ok = true;
+        handled = true;
+      }
+    }
+
+    void onerror(Event _) {
+      handled = true;
+    }
+
+    req.onsuccess = onsuccess.toJS;
+    req.onerror = onerror.toJS;
+    FutureOr<bool> waitResult() {
+      if (handled) return ok;
+      return Future.delayed(const Duration(milliseconds: 1), waitResult);
+    }
+
+    await Future.microtask(waitResult);
+  }
+
+  Future<void> openKeyCursor(String table, void Function(IDBCursor) callback,
+      {JSAny? query, String? direction, bool readwrite = false}) async {
+    await init();
+    final tx = _db.transaction(
+        [table.toJS].toJS, readwrite ? 'readwrite' : 'readonly');
+    final store = tx.objectStore(table);
+    final req = query != null && direction != null
+        ? store.openKeyCursor(query, direction!)
+        : query != null
+            ? store.openKeyCursor(query)
+            : store.openKeyCursor();
+    bool ok = false;
+    bool handled = false;
+    void onsuccess(Event _) {
+      if (req.result != null) {
+        final cursor = req.result as IDBCursor;
+        callback(cursor);
+      } else {
+        ok = true;
+        handled = true;
+      }
+    }
+
+    void onerror(Event _) {
+      handled = true;
+    }
+
+    req.onsuccess = onsuccess.toJS;
+    req.onerror = onerror.toJS;
+    FutureOr<bool> waitResult() {
+      if (handled) return ok;
+      return Future.delayed(const Duration(milliseconds: 1), waitResult);
+    }
+
+    await Future.microtask(waitResult);
+  }
+
+  Future<JSAny?> put(String table, JSAny value, {JSAny? key}) async {
+    await init();
+    final tx = _db.transaction([table.toJS].toJS, 'readwrite');
+    final store = tx.objectStore(table);
+    final req = key == null ? store.put(value) : store.put(value, key);
+    return await _waitRequest(req);
+  }
+}