Flutter file picker

bytes_util.dart

import 'dart:typed_data';

import 'package:crypto/crypto.dart' as crypto;
import 'package:meta/meta.dart';

@internal
abstract final class BytesUtil {
  /// Extract hash from a [Uint8List] and convert it to a hex string.
  static String sha256(Uint8List bytes) {
    if (bytes.isEmpty) return 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855';
    crypto.Digest digest = crypto.sha256.convert(bytes);
    return digest.toString();
  }
}

pick_file.dart

import 'package:file_picker/file_picker.dart' as file_picker;

/// Pick a file to attach to the next message.
void _pickFile() => runZonedGuarded<void>(
  () async {
    const allowedExtensions = <String>{
      'txt',
      'pdf',
      'doc',
      'docx',
      'png',
      'jpg',
      'jpeg',
      'gif',
      'bpm',
      //'webp',
      'heic',
      'heics',
      'heif',
      'heifs',
      'hif',
    };
    const maxFileSize = 20 * 1024 * 1024; // 20 MB
    const maxFileCount = 15; // 15 files max can be attached at once
    final file_picker.FilePickerResult? result;
    try {
      final filePicker = file_picker.FilePicker.platform;
      result = await filePicker.pickFiles(
        dialogTitle: _localization.chatInputTooltipAttachFile,
        allowMultiple: false, // allow multiple files to be selected
        withData: true, // bytes for web/mobile preview
        type: file_picker.FileType.custom,
        readSequential: false,
        withReadStream: false,
        allowedExtensions: allowedExtensions.toList(growable: false),
      );
    } on Object catch (e, s) {
      l.w('File picker not available: $e', s);
      if (_disposed) return;
      // ignore: use_build_context_synchronously
      ErrorUtil.displayErrorSnackBar(context, 'Can\'t pick files', s);
      return;
    }
    if (_disposed) return;
    if (_chatController.state case ChatState$Processing(blockInput: true)) return;
    if (result == null || result.count < 1 || result.files.isEmpty) return;
    final attachedAt = DateTime.now().toUtc();
    final stopwatch = Stopwatch()..start();
    final newFiles =
        await Stream<file_picker.PlatformFile>.fromIterable(result.files)
            .take(maxFileCount)
            .asyncMap<AttachmentFile>((e) async {
              if (stopwatch.elapsed > Duration(milliseconds: 8)) {
                // Releave the event loop
                await Future<void>.delayed(Duration.zero);
                stopwatch.reset();
              }
              final name = path.basename(e.name);
              var extension = e.extension?.toLowerCase() ?? path.extension(name).toLowerCase();
              if (extension.startsWith('.')) extension = extension.substring(1);
              if (extension.isEmpty) extension = 'bin';
              final type = AttachmentFile.extensionToType(extension);
              var bytes = e.bytes ?? Uint8List(0);
              if (bytes.length > maxFileSize) bytes = Uint8List(0);
              return AttachmentFile(
                hash: BytesUtil.sha256(bytes),
                name: name,
                extension: extension,
                type: type,
                bytes: bytes,
                attachedAt: attachedAt,
              );
            })
            .where(
              (f) =>
                  f.name.isNotEmpty &&
                  f.extension.isNotEmpty &&
                  f.bytes.isNotEmpty &&
                  f.size > 0 &&
                  f.size <= maxFileSize,
            )
            .toList();
    stopwatch.stop();
    if (_disposed || newFiles.isEmpty) return;
    // All previous attachments that are not in the new list
    // To avoid duplicates
    final attachmentsMap = <String, AttachmentFile>{
      // Previous attachments
      for (final f in _attachments.value) f.hash: f,
      // New attachments
      for (final f in newFiles) f.hash: f,
    };
    var attachments = attachmentsMap.values.toList(growable: false)
      ..sort((a, b) => b.attachedAt.compareTo(a.attachedAt));
    if (_disposed) return;
    if (attachments.length > maxFileCount) attachments = attachments.take(maxFileCount).toList(growable: false);
    _attachments.value = attachments;
  },
  (e, s) {
    l.e('Error while picking file: $e', s);
    if (_disposed) return;
    // ignore: use_build_context_synchronously
    ErrorUtil.displayErrorSnackBar(context, e, s);
  },
);