feat: support max running tasks config (#112)

ui/flutter/lib/api/api.dart

@@ -73,15 +73,12 @@ Future<T> _parse<T>(
 ) async {
   try {
     var resp = await fetch();
-    if (fromJsonT != null) {
-      final result = Result<T>.fromJson(resp.data, fromJsonT);
-      if (result.code == 0) {
-        return result.data as T;
-      } else {
-        throw Exception(result);
-      }
+    fromJsonT ??= (json) => null as T;
+    final result = Result<T>.fromJson(resp.data, fromJsonT);
+    if (result.code == 0) {
+      return result.data as T;
     } else {
-      return null as T;
+      throw Exception(result);
     }
   } on DioError catch (e) {
     throw Exception(Result(code: 1000, msg: e.message));

ui/flutter/lib/api/model/downloader_config.dart

@@ -5,6 +5,7 @@ part 'downloader_config.g.dart';
 @JsonSerializable(explicitToJson: true)
 class DownloaderConfig {
   String downloadDir = '';
+  int maxRunning = 0;
   ProtocolConfig protocolConfig = ProtocolConfig();
   ExtraConfig extra = ExtraConfig();
 

ui/flutter/lib/api/model/downloader_config.g.dart

@@ -9,6 +9,7 @@ part of 'downloader_config.dart';
 DownloaderConfig _$DownloaderConfigFromJson(Map<String, dynamic> json) =>
     DownloaderConfig()
       ..downloadDir = json['downloadDir'] as String
+      ..maxRunning = json['maxRunning'] as int
       ..protocolConfig = ProtocolConfig.fromJson(
           json['protocolConfig'] as Map<String, dynamic>?)
       ..extra = ExtraConfig.fromJson(json['extra'] as Map<String, dynamic>?);
@@ -16,6 +17,7 @@ DownloaderConfig _$DownloaderConfigFromJson(Map<String, dynamic> json) =>
 Map<String, dynamic> _$DownloaderConfigToJson(DownloaderConfig instance) =>
     <String, dynamic>{
       'downloadDir': instance.downloadDir,
+      'maxRunning': instance.maxRunning,
       'protocolConfig': instance.protocolConfig.toJson(),
       'extra': instance.extra.toJson(),
     };

ui/flutter/lib/api/model/task.dart

@@ -1,12 +1,10 @@
 import 'package:json_annotation/json_annotation.dart';
 
 import 'meta.dart';
-import 'options.dart';
-import 'resource.dart';
 
 part 'task.g.dart';
 
-enum Status { ready, running, pause, error, done }
+enum Status { ready, running, pause, wait, error, done }
 
 @JsonSerializable(explicitToJson: true)
 class Task {

ui/flutter/lib/api/model/task.g.dart

@@ -28,6 +28,7 @@ const _$StatusEnumMap = {
   Status.ready: 'ready',
   Status.running: 'running',
   Status.pause: 'pause',
+  Status.wait: 'wait',
   Status.error: 'error',
   Status.done: 'done',
 };