fediverse-archiving-tools/bin/image_archiver.dart

import 'dart:convert';
import 'dart:io';

import 'package:path/path.dart' as p;
import 'package:uuid/uuid.dart';

import 'extensions.dart';
import 'friendica_client.dart';
import 'models.dart';

class ImageArchiver {
  final FriendicaClient client;
  final _images = <String, ImageEntry>{};
  late final Directory imageDirectory;

  List<ImageEntry> get images => List.unmodifiable(_images.values);

  ImageArchiver(this.client, Directory baseDirectory) {
    final imageDirPath = p.join(baseDirectory.path, 'images');
    imageDirectory = Directory(imageDirPath);
    imageDirectory.createSync(recursive: true);
  }

  bool addDirectEntries(ImageEntry entry) {
    final alreadyExists = _images.containsKey(entry.url);
    _images[entry.url] = entry;
    return alreadyExists;
  }

  Future<List<ImageEntry>> addEntryImages(FriendicaEntry entry) async {
    final imageEntries = <ImageEntry>[];
    for (final imageUrl in entry.images) {
      if (_images.containsKey(imageUrl)) {
        continue;
      }
      final url = Uri.parse(imageUrl);
      final imageResponse = await client.getUrl(url);
      if (imageResponse.isFailure) {
        print(imageResponse.error);
        continue;
      }

      if (imageResponse.value.statusCode == 200) {
        final contents = <int>[];
        await for (var data in imageResponse.value) {
          contents.addAll(data);
        }
        final extension = calculateExtensions(contents);
        final filename = Uuid().v4().replaceAll('-', '') + extension;
        final filePath = p.join(imageDirectory.path, filename);
        await File(filePath).writeAsBytes(contents);
        final newEntry = ImageEntry(
            postId: entry.id.toString(),
            localFilename: filename,
            url: imageUrl);
        _images[imageUrl] = newEntry;
        imageEntries.add(newEntry);
      } else {
        print(
            'Error response attempting to retrieve image $imageUrl: ${imageResponse.value.statusCode}');
      }
    }

    return imageEntries;
  }

  String calculateExtensions(List<int> imageBytes) {
    // Using table from https://www.sparkhound.com/blog/detect-image-file-types-through-byte-arrays
    final bmp = ascii.encode("BM").toList(); // BMP
    final gif = ascii.encode("GIF").toList(); // GIF
    const png = <int>[137, 80, 78, 71]; // PNG
    const tiff = <int>[73, 73, 42]; // TIFF
    const tiff2 = <int>[77, 77, 42]; // TIFF
    const jpeg = <int>[255, 216, 255, 224]; // jpeg
    const jpeg2 = <int>[255, 216, 255, 225]; // jpeg canon

    final firstFour = imageBytes.sublist(0, 4);

    if (firstFour.equals(jpeg) || firstFour.equals(jpeg2)) {
      return '.jpg';
    }

    if (firstFour.equals(png)) {
      return '.png';
    }

    final firstThree = imageBytes.sublist(0, 3);
    if (firstThree.equals(gif)) {
      return '.gif';
    }

    if (firstThree.equals(tiff) || firstThree.equals(tiff2)) {
      return '.tif';
    }

    final firstTwo = imageBytes.sublist(0, 2);
    if (firstTwo.equals(bmp)) {
      return '.bmp';
    }

    return '';
  }
}