Toolkit2/Toolkit.Foundation/Configurations/WritableJsonConfigurationBuilder.cs

using Json.Patch;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Text.Json;
using System.Text.Json.Serialization;
using JsonSerializer = System.Text.Json.JsonSerializer;

namespace Toolkit.Foundation
{
    public class WritableJsonConfigurationBuilder : IWritableJsonConfigurationBuilder
    {
        private readonly List<IWritableJsonConfigurationDescriptor> descriptors = new();

        public Stream? DefaultFileStream { get; private set; }

        public IReadOnlyCollection<IWritableJsonConfigurationDescriptor> Descriptors => new ReadOnlyCollection<IWritableJsonConfigurationDescriptor>(descriptors);

        public IWritableJsonConfigurationBuilder AddDefaultConfiguration<TConfiguration>(string Key) where TConfiguration : class
        {
            descriptors.Add(new WritableJsonConfigurationDescriptor(typeof(TConfiguration), Key));
            return this;
        }

        public IWritableJsonConfigurationBuilder AddDefaultFileStream(Stream stream)
        {
            DefaultFileStream = stream;
            return this;
        }

        public void Build(string path)
        {
            JObject? sourceDocument = new();
            if (TryLoadSource(out string? defaultContent))
            {
                sourceDocument = JObject.Parse(defaultContent!);
            }

            JObject? targetDocument = new();
            if (TryLoadTarget(path, out string? targetContent))
            {
                targetDocument = JObject.Parse(targetContent!);
            }

            foreach (IWritableJsonConfigurationDescriptor? descriptor in descriptors)
            {
                if (sourceDocument.SelectToken($"$.{descriptor.Key}") is JToken sourceSection)
                {
                    if (targetDocument.SelectToken($"$.{descriptor.Key}") is JToken targetSection)
                    {
                        object? source = JsonSerializer.Deserialize(JsonConvert.SerializeObject(sourceSection), descriptor.ConfigurationType);
                        object? target = JsonSerializer.Deserialize(JsonConvert.SerializeObject(targetSection), descriptor.ConfigurationType);

                        JsonPatch? patch = source.CreatePatch(target);

                        object? sourcePatched = patch.Apply(source);
                        targetSection.Replace(JToken.Parse(JsonSerializer.Serialize(sourcePatched, new JsonSerializerOptions { DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull })));
                    }
                    else
                    {
                        object? source = JsonSerializer.Deserialize(JsonConvert.SerializeObject(sourceSection), descriptor.ConfigurationType);
                        targetDocument.Add(descriptor.Key, JToken.Parse(JsonSerializer.Serialize(source, new JsonSerializerOptions { DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull })));
                    }
                }
                else
                {
                    object? configuration = Activator.CreateInstance(descriptor.ConfigurationType);
                    targetDocument.Add(descriptor.Key, JToken.Parse(JsonSerializer.Serialize(configuration, new JsonSerializerOptions { DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull })));
                }
            }

            using FileStream? fileStream = new(path, FileMode.Create, FileAccess.Write);
            using StreamWriter streamWriter = new(fileStream);
            using JsonTextWriter writer = new(streamWriter) { Formatting = Formatting.Indented };
            targetDocument.WriteTo(writer);
        }

        private bool TryLoadTarget(string path, [MaybeNull] out string? content)
        {
            if (File.Exists(path))
            {
                using FileStream? fileStream = new(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
                using StreamReader? streamReader = new(fileStream);
                content = streamReader.ReadToEnd();
                return true;
            }

            content = null;
            return false;
        }

        private bool TryLoadSource([MaybeNull] out string? content)
        {
            if (DefaultFileStream is Stream fileStream)
            {
                using StreamReader? streamReader = new(fileStream);
                content = streamReader.ReadToEnd();
                return true;
            }

            content = null;
            return false;
        }
    }

}