using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

using System.Collections.ObjectModel;

​

using System.Text.Json;

using System.Text.Json.Serialization;

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/76937386/c-sharp-polymorphic-deserialization-of-bookmarks-file

​

#nullable enable

​

public abstract class BookmarkElement

{

    public BookmarkElement() {}

    [JsonPropertyName("date_added")]

    public string DateAdded { get; set; }

    [JsonPropertyName("date_last_used")]

    public string DateLastUsed { get; set; }

    [JsonPropertyName("guid")]

    public string Guid { get; set; }

    [JsonPropertyName("id")]

    public string Id { get; set; }

    [JsonPropertyName("name")]

    public string Name { get; set; }

    [JsonPropertyName("type")]

    public string Type { get; set; }

}

​

public class Bookmark : BookmarkElement

{

    public Bookmark() { }

    [JsonPropertyName("url")]

    public string Url {get; set;}

}

​

public class Folder : BookmarkElement

{

    public Folder() {}

    [JsonPropertyName("date_modified")]

    public string DateModified { get; set; }

    [JsonPropertyName("children")]

    public List<BookmarkElement> FolderElements {get; set;}

}

​

public class Root : BookmarkElement

{

    public Root() {}

    [JsonPropertyName("date_modified")]

    public string DateModified { get; set; }

    [JsonPropertyName("children")]

    public List<BookmarkElement> RootFolder { get; set; }

}

​

public class BookmarkModel

{

    public BookmarkModel() {}

    [JsonPropertyName("checksum")]

    public string Checksum { get; set; }

    [JsonPropertyName("roots")]

    public Dictionary<string, Root> Roots { get; set; }

    [JsonPropertyName("version")]

    public int Version { get; set; }

}

​

public class BookmarkElementConverter : JsonConverter<BookmarkElement>

{

    public override BookmarkElement? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

    {

        if(reader.TokenType != JsonTokenType.StartObject) 

            throw new JsonException();

​

        using (var jsonDocument = JsonDocument.ParseValue(ref reader))

        {

            if(!jsonDocument.RootElement.TryGetProperty("type", out var typeProperty)) 

                throw new JsonException();

            return typeProperty.GetString() switch

            {

                "url" => jsonDocument.RootElement.Deserialize<Bookmark>(options),

                "folder" => jsonDocument.RootElement.Deserialize<Folder>(options),

                _ => throw new JsonException(),

            };

        }

    }

​

    public override void Write(Utf8JsonWriter writer, BookmarkElement value, JsonSerializerOptions options) =>

        JsonSerializer.Serialize(writer, value, value.GetType(), options);

}

​

    class TestClass

    {

        public static void Test()

        {

            var json = GetJson();

            var options = new JsonSerializerOptions

            {

                Converters = { new BookmarkElementConverter() },

                // Add any additional required options here:

                WriteIndented = true,

            };

            var model = JsonSerializer.Deserialize<BookmarkModel>(json, options);

​

            var json2 = JsonSerializer.Serialize(model, options);

            Console.WriteLine("Re-serialized {0}", model);

            Console.WriteLine(json2);

        }

        static string GetJson() =>

            """

            {

               "checksum": "cc1f5c62ec7814f7928e2befab26c311",

               "roots": {

                  "bookmark_bar": {

                     "children": [ {

                        "children": [  ],

                        "date_added": "13335767383821356",

                        "date_last_used": "0",

                        "date_modified": "13335767383821356",

                        "guid": "efeb5549-612d-4656-8982-a17069075213",

                        "id": "13",

                        "name": "test",

                        "type": "folder"

                     }, {

                        "date_added": "13335767548044529",

                        "date_last_used": "0",

                        "guid": "df7a482b-c1c5-4aa2-af8e-8cee539513d9",

                        "id": "15",

                        "name": "DuckDuckGo — Privacy, simplified.",

                        "type": "url",

                        "url": "https://duckduckgo.com/"

                     } ],

                     "date_added": "13335764354355200",

                     "date_last_used": "0",

                     "date_modified": "13335767548044529",

                     "guid": "0bc5d13f-2cba-5d74-951f-3f233fe6c908",

                     "id": "1",

                     "name": "Bookmarks bar",

                     "type": "folder"

                  },

                  "other": {

                     "children": [  ],

                     "date_added": "13335764354355201",

                     "date_last_used": "0",

                     "date_modified": "0",

                     "guid": "82b081ec-3dd3-529c-8475-ab6c344590dd",

                     "id": "2",

                     "name": "Other bookmarks",

                     "type": "folder"

                  },

                  "synced": {

                     "children": [  ],

                     "date_added": "13335764354355202",

                     "date_last_used": "0",

                     "date_modified": "0",

                     "guid": "4cf2e351-0e85-532b-bb37-df045d8f8d0f",

                     "id": "3",

                     "name": "Mobile bookmarks",

                     "type": "folder"

                  }

               },

               "version": 1

            }

            """;

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}), {2}", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion);

            Console.WriteLine("System.Text.Json version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​