feat(mobile): platform image providers (#20927)

* platform image providers

* use key

* fix cache manager

* more logs, cancel on dispose instead

* split into separate files

* fix saving to cache

* cancel multi-stage provider

* refactored `getInitialImage`

* only wait for disposal for full images

* cached image works

* formatting

* lower asset viewer ram usage

---------

Co-authored-by: Alex <alex.tran1502@gmail.com>

mobile/lib/infrastructure/loaders/remote_image_request.dart

@@ -0,0 +1,146 @@
+part of 'image_request.dart';
+
+class RemoteImageRequest extends ImageRequest {
+  static final log = Logger('RemoteImageRequest');
+  static final client = HttpClient()..maxConnectionsPerHost = 32;
+  final RemoteCacheManager? cacheManager;
+  final String uri;
+  final Map<String, String> headers;
+  HttpClientRequest? _request;
+
+  RemoteImageRequest({required this.uri, required this.headers, this.cacheManager});
+
+  @override
+  Future<ImageInfo?> load(ImageDecoderCallback decode, {double scale = 1.0}) async {
+    if (_isCancelled) {
+      return null;
+    }
+
+    // TODO: the cache manager makes everything sequential with its DB calls and its operations cannot be cancelled,
+    //  so it ends up being a bottleneck.  We only prefer fetching from it when it can skip the DB call.
+    final cachedFileImage = await _loadCachedFile(uri, decode, scale, inMemoryOnly: true);
+    if (cachedFileImage != null) {
+      return cachedFileImage;
+    }
+
+    try {
+      Stopwatch? stopwatch;
+      if (!kReleaseMode) {
+        stopwatch = Stopwatch()..start();
+      }
+      final buffer = await _downloadImage(uri);
+      if (buffer == null) {
+        return null;
+      }
+      if (!kReleaseMode) {
+        stopwatch!.stop();
+        debugPrint('Remote image download $requestId took ${stopwatch.elapsedMilliseconds}ms for $uri');
+      }
+      return await _decodeBuffer(buffer, decode, scale);
+    } catch (e) {
+      if (_isCancelled) {
+        return null;
+      }
+
+      final cachedFileImage = await _loadCachedFile(uri, decode, scale, inMemoryOnly: false);
+      if (cachedFileImage != null) {
+        return cachedFileImage;
+      }
+
+      rethrow;
+    } finally {
+      _request = null;
+    }
+  }
+
+  Future<ImmutableBuffer?> _downloadImage(String url) async {
+    if (_isCancelled) {
+      return null;
+    }
+
+    final request = _request = await client.getUrl(Uri.parse(url));
+    if (_isCancelled) {
+      request.abort();
+      return _request = null;
+    }
+
+    for (final entry in headers.entries) {
+      request.headers.set(entry.key, entry.value);
+    }
+    final response = await request.close();
+    if (_isCancelled) {
+      return null;
+    }
+    final bytes = Uint8List(response.contentLength);
+    int offset = 0;
+    final subscription = response.listen((List<int> chunk) {
+      // this is important to break the response stream if the request is cancelled
+      if (_isCancelled) {
+        throw StateError('Cancelled request');
+      }
+      bytes.setAll(offset, chunk);
+      offset += chunk.length;
+    }, cancelOnError: true);
+    cacheManager?.putStreamedFile(url, response);
+    await subscription.asFuture();
+    return await ImmutableBuffer.fromUint8List(bytes);
+  }
+
+  Future<ImageInfo?> _loadCachedFile(
+    String url,
+    ImageDecoderCallback decode,
+    double scale, {
+    required bool inMemoryOnly,
+  }) async {
+    final cacheManager = this.cacheManager;
+    if (_isCancelled || cacheManager == null) {
+      return null;
+    }
+
+    final file = await (inMemoryOnly ? cacheManager.getFileFromMemory(url) : cacheManager.getFileFromCache(url));
+    if (_isCancelled || file == null) {
+      return null;
+    }
+
+    try {
+      final buffer = await ImmutableBuffer.fromFilePath(file.file.path);
+      return await _decodeBuffer(buffer, decode, scale);
+    } catch (e) {
+      log.severe('Failed to decode cached image', e);
+      _evictFile(url);
+      return null;
+    }
+  }
+
+  Future<void> _evictFile(String url) async {
+    try {
+      await cacheManager?.removeFile(url);
+    } catch (e) {
+      log.severe('Failed to remove cached image', e);
+    }
+  }
+
+  Future<ImageInfo?> _decodeBuffer(ImmutableBuffer buffer, ImageDecoderCallback decode, scale) async {
+    if (_isCancelled) {
+      buffer.dispose();
+      return null;
+    }
+    final codec = await decode(buffer);
+    if (_isCancelled) {
+      buffer.dispose();
+      codec.dispose();
+      return null;
+    }
+    final frame = await codec.getNextFrame();
+    return ImageInfo(image: frame.image, scale: scale);
+  }
+
+  @override
+  void _onCancelled() {
+    _request?.abort();
+    _request = null;
+    if (!kReleaseMode) {
+      debugPrint('Cancelled remote image request $requestId for $uri');
+    }
+  }
+}