Use System.Text.Json to serialize and deserialize JSON text

src/Imghoard.Tests/Formatters/Base64FileFormatterTest.cs

@@ -0,0 +1,30 @@
+using System.Text;
+using System.Text.Json;
+using Imghoard.Models;
+using Xunit;
+
+namespace Imghoard.Tests.Formatters
+{
+    public class Base64FileFormatterTest
+    {
+        [Fact]
+        public void FormatTest()
+        {
+            using var pixel = typeof(Base64FileFormatterTest).Assembly
+                .GetManifestResourceStream("Imghoard.Tests.Resources.BlackPixel.png");
+
+            var bytes = JsonSerializer.SerializeToUtf8Bytes(
+                new PostImage
+                {
+                    Stream = pixel
+                },
+                ImghoardClient.JsonSerializerOptions
+            );
+
+            Assert.Equal(
+                @"{""Data"":""data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAAAAAA6fptVAAAACklEQVR4nGNiAAAABgADNjd8qAAAAABJRU5ErkJggg==""}",
+                Encoding.UTF8.GetString(bytes)
+            );
+        }
+    }
+}

src/Imghoard.Tests/Imghoard.Tests.csproj

@@ -1,12 +1,18 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <OutputType>WinExe</OutputType>
     <TargetFramework>netcoreapp3.0</TargetFramework>
-    <ApplicationIcon />
-    <StartupObject />
+    <IsPackable>false</IsPackable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Remove="Resources\BlackPixel.png" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <EmbeddedResource Include="Resources\BlackPixel.png" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">

src/Imghoard/Formatters/Base64FileFormatter.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Buffers;
+using System.Buffers.Text;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Miki.Utils.Imaging.Headers;
+using Miki.Utils.Imaging.Headers.Models;
+
+namespace Imghoard.Formatters
+{
+    internal sealed class Base64FileFormatter : JsonConverter<Stream>
+    {
+        public override Stream Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            throw new NotSupportedException("Reading a Base64 stream is not supported.");
+        }
+
+        public override void Write(Utf8JsonWriter writer, Stream value, JsonSerializerOptions options)
+        {
+            byte[] data;
+
+            if (value is MemoryStream memoryStream)
+            {
+                data = memoryStream.ToArray();
+            }
+            else
+            {
+                // TODO: Check if this can be improved.
+                using var ms = new MemoryStream();
+                value.Position = 0;
+                value.CopyTo(ms);
+                data = ms.ToArray();
+            }
+
+            var (supported, name) = IsSupported(data);
+
+            if (!supported)
+            {
+                throw new NotSupportedException($"File extension {name} is not supported. Supported extensions: png, jpeg, gif.");
+            }
+
+            var prefix = $"data:image/{name};base64,";
+
+            var prefixLength = Encoding.UTF8.GetByteCount(prefix);
+            var encodingLength = Base64.GetMaxEncodedToUtf8Length(data.Length);
+            var length = prefixLength + encodingLength;
+
+            var destination = ArrayPool<byte>.Shared.Rent(length);
+            var span = destination.AsSpan();
+
+            try
+            {
+                Encoding.UTF8.GetBytes(prefix, span);
+
+                var status = Base64.EncodeToUtf8(data, span.Slice(prefixLength), out var consumed, out var written);
+                Debug.Assert(status == OperationStatus.Done);
+                Debug.Assert(consumed == data.Length);
+
+                writer.WriteStringValue(span.Slice(0, prefixLength + written));
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(destination);
+            }
+        }
+
+        private static (bool supported, string name) IsSupported(byte[] image)
+        {
+            if (ImageHeaders.Validate(image, ImageType.Png))
+            {
+                return (true, "png");
+            }
+
+            if (ImageHeaders.Validate(image, ImageType.Jpeg))
+            {
+                return (true, "jpeg");
+            }
+
+            if (ImageHeaders.Validate(image, ImageType.Gif89a) || ImageHeaders.Validate(image, ImageType.Gif87a))
+            {
+                return (true, "gif");
+            }
+
+            return (false, null);
+        }
+    }
+}

src/Imghoard/Imghoard.csproj

@@ -5,10 +5,9 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Miki.Net.Http" Version="2.1.0" />
     <PackageReference Include="Miki.Utils.Imaging.Headers" Version="1.0.0" />
-    <PackageReference Include="Newtonsoft.Json" Version="12.0.2" />
     <PackageReference Include="System.Drawing.Common" Version="4.5.1" />
+    <PackageReference Include="System.Text.Json" Version="4.6.0" />
   </ItemGroup>
 
 </Project>