immich/mobile/lib/providers/image/immich_local_thumbnail_provider.dart

import 'dart:async';
import 'dart:ui' as ui;

import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter_cache_manager/flutter_cache_manager.dart';
import 'package:immich_mobile/providers/image/cache/thumbnail_image_cache_manager.dart';

import 'package:flutter/foundation.dart';
import 'package:flutter/painting.dart';
import 'package:immich_mobile/entities/asset.entity.dart';
import 'package:photo_manager/photo_manager.dart' show ThumbnailSize;
import 'package:logging/logging.dart';

/// The local image provider for an asset
/// Only viable
class ImmichLocalThumbnailProvider extends ImageProvider<ImmichLocalThumbnailProvider> {
  final Asset asset;
  final int height;
  final int width;
  final CacheManager? cacheManager;
  final Logger log = Logger("ImmichLocalThumbnailProvider");
  final String? userId;

  ImmichLocalThumbnailProvider({
    required this.asset,
    this.height = 256,
    this.width = 256,
    this.cacheManager,
    this.userId,
  }) : assert(asset.local != null, 'Only usable when asset.local is set');

  /// Converts an [ImageProvider]'s settings plus an [ImageConfiguration] to a key
  /// that describes the precise image to load.
  @override
  Future<ImmichLocalThumbnailProvider> obtainKey(ImageConfiguration configuration) {
    return SynchronousFuture(this);
  }

  @override
  ImageStreamCompleter loadImage(ImmichLocalThumbnailProvider key, ImageDecoderCallback decode) {
    final cache = cacheManager ?? ThumbnailImageCacheManager();
    return MultiImageStreamCompleter(
      codec: _codec(key.asset, cache, decode),
      scale: 1.0,
      informationCollector: () sync* {
        yield ErrorDescription(key.asset.fileName);
      },
    );
  }

  // Streams in each stage of the image as we ask for it
  Stream<ui.Codec> _codec(Asset assetData, CacheManager cache, ImageDecoderCallback decode) async* {
    final cacheKey = '$userId${assetData.localId}${assetData.checksum}$width$height';
    final fileFromCache = await cache.getFileFromCache(cacheKey);
    if (fileFromCache != null) {
      try {
        final buffer = await ui.ImmutableBuffer.fromFilePath(fileFromCache.file.path);
        final codec = await decode(buffer);
        yield codec;
        return;
      } catch (error) {
        log.severe('Found thumbnail in cache, but loading it failed', error);
      }
    }

    final thumbnailBytes = await assetData.local?.thumbnailDataWithSize(ThumbnailSize(width, height), quality: 80);
    if (thumbnailBytes == null) {
      throw StateError("Loading thumb for local photo ${assetData.fileName} failed");
    }

    final buffer = await ui.ImmutableBuffer.fromUint8List(thumbnailBytes);
    final codec = await decode(buffer);
    yield codec;
    await cache.putFile(cacheKey, thumbnailBytes);
  }

  @override
  bool operator ==(Object other) {
    if (identical(this, other)) return true;
    if (other is ImmichLocalThumbnailProvider) {
      return asset.id == other.asset.id && asset.localId == other.asset.localId;
    }
    return false;
  }

  @override
  int get hashCode => Object.hash(asset.id, asset.localId);
}