fis_lib_vid/lib/data_host/native/data_host.dart

import 'dart:io';
import 'dart:isolate';
import 'dart:typed_data';

import 'package:fis_vid/data_host/interface/data_host.dart';
import 'package:fis_vid/data_host/vid_download.dart';
import 'package:flutter/painting.dart';
import 'package:flutter/rendering.dart';
import 'package:image/image.dart' as img;
import 'package:path_provider/path_provider.dart';
import 'package:vid/us/vid_us_image.dart';
import 'package:fis_vid/processors/base.dart';
import 'package:vid/us/vid_us_image_data.dart';
import 'package:vid/us/vid_us_probe.dart';

class VidDataHost implements VidDataHostInterface {
  VidDataHost(this.url);
  static const _kStorageDir = 'ExamRecords';

  VidUsImageData? _data;

  @override
  final String url;

  @override
  VidUsProbe get probe => _data!.probe;

  @override
  int get frameCount => _data!.imageCount;

  @override
  Future<VidUsImageData?> getData() async => _data;

  @override
  Future<VidDataHostLoadInfo?> load() async {
    final vidFileBuffer = await _loadVidFile(url);
    if (vidFileBuffer == null) return null;

    _data = VidUsImageData(vidFileBuffer);
    return VidDataHostLoadInfo(probe);
  }

  @override
  Future<VidUsImage> getFrame<TProcessor extends VidFrameProcessor>(
    int index, {
    List<TProcessor>? processors,
  }) async {
    if (_data == null) {
      throw Exception(
          "[VidDataHost] getFrame: must call load first and data is not null.");
    }

    final frame = _data!.getImage(index);
    return VidFrameProcessor.processFrame(frame, processors);
  }

  @override
  Future<void> release() async {
    _data = null;
  }

  Future<Uint8List?> _loadVidFile(String url) async {
    try {
      final name = url.split('/').last.split('.').first;
      final fileName = '$name.dat';
      final cachePath = await _getStoragePath(fileName);
      var file = File(cachePath);
      if (await file.exists()) {
        final buffer = await file.readAsBytes();
        return buffer;
      } else {
        final buffer = await VidFileDownloader.download(url);
        if (buffer != null) {
          file = await file.create(recursive: true);
          file.writeAsBytes(buffer);
        }
        return buffer;
      }
    } catch (e) {
      return null;
    }
  }

  Future<String> _getStoragePath(String fileName) async {
    Directory? dir;
    if (Platform.isAndroid) {
      dir = await getExternalStorageDirectory();
    }
    dir ??= await getApplicationDocumentsDirectory();
    return "${dir.path}/$_kStorageDir/$fileName";
  }
}