download and downloading page

lib/appdata.dart

@@ -1,6 +1,9 @@
 import 'dart:convert';
 import 'dart:io';
 
+import 'package:flutter/services.dart';
+import 'package:path_provider/path_provider.dart';
+
 import 'foundation/app.dart';
 import 'network/models.dart';
 
@@ -9,9 +12,18 @@ class _Appdata {
 
   var searchOptions = SearchOptions();
 
+  Map<String, dynamic> settings = {
+    "downloadPath": null,
+    "downloadSubPath": r"/${id}-p${index}.${ext}",
+    "tagsWeight": "",
+    "useTranslatedNameForDownload": false,
+  };
+
   void writeData() async {
     await File("${App.dataPath}/account.json")
         .writeAsString(jsonEncode(account));
+    await File("${App.dataPath}/settings.json")
+        .writeAsString(jsonEncode(settings));
   }
 
   Future<void> readData() async {
@@ -19,6 +31,39 @@ class _Appdata {
     if (file.existsSync()) {
       account = Account.fromJson(jsonDecode(await file.readAsString()));
     }
+    final settingsFile = File("${App.dataPath}/settings.json");
+    if (settingsFile.existsSync()) {
+      var json = jsonDecode(await settingsFile.readAsString());
+      for(var key in json.keys) {
+        settings[key] = json[key];
+      }
+    }
+    if(settings["downloadPath"] == null) {
+      settings["downloadPath"] = await _defaultDownloadPath;
+    }
+  }
+
+  String get downloadPath => settings["downloadPath"];
+
+  Future<String> get _defaultDownloadPath async{
+    if(App.isAndroid) {
+      var externalStoragePaths = await getExternalStorageDirectories(type: StorageDirectory.downloads);
+      var res = externalStoragePaths?.first.path;
+      res ??= (await getExternalStorageDirectory())!.path;
+      return "$res/pixes";
+    } else if (App.isWindows){
+      var res = await const MethodChannel("pixes/picture_folder").invokeMethod("");
+      if(res != "error") {
+        return res + "/pixes";
+      }
+    } else if (App.isMacOS || App.isLinux) {
+      var downloadPath = (await getDownloadsDirectory())?.path;
+      if(downloadPath != null) {
+        return "$downloadPath/pixes";
+      }
+    }
+
+    return "${App.dataPath}/download";
   }
 }