stitchaton/src/Oh.My.Stitcher/Program.cs

using System.Buffers;
using System.IO.Pipelines;
using Microsoft.AspNetCore.Http.Json;
using NetVips;
using Oh.My.Stitcher;
using Validation;
using ZLogger;

WebApplicationBuilder builder = WebApplication.CreateSlimBuilder(args);
builder.Logging.ClearProviders().AddZLoggerConsole();
builder.Services.Configure<JsonOptions>(options =>
{
  options.SerializerOptions.TypeInfoResolver = StitchSerializerContext.Default;
});
WebApplication app = builder.Build();

ILoggerFactory loggerFactory = app.Services.GetRequiredService<ILoggerFactory>();
ILogger logger = loggerFactory.CreateLogger<Program>();

string? tilesDirectory = Environment.GetEnvironmentVariable("ASSET_PATH_RO");

// sanity check
Assumes.NotNullOrEmpty(tilesDirectory);
Assumes.True(File.Exists(Path.Combine(tilesDirectory, "A1.png")));
Assumes.True(File.Exists(Path.Combine(tilesDirectory, "AE55.png")));

app.UseDefaultFiles();
app.UseStaticFiles();
app.MapPost("/api/image/generate", (Stitch request) =>
{
  Pipe pipe = new();
  _ = Task.Run(async () =>
  {
    List<Image> images = [];
    try
    {
      using Image image = Tile.Create(in request, tilesDirectory, images, logger);
      Pipe innerPipe = new();
      _ = Task.Run(async () =>
      {
        while( true )
        {
          ReadResult result = await innerPipe.Reader.ReadAsync();
          ReadOnlySequence<byte> buffer = result.Buffer;
          if(!buffer.IsEmpty )
          {
            foreach( ReadOnlyMemory<byte> segment in buffer )
            {
              await pipe.Writer.WriteAsync(segment);
            }
            innerPipe.Reader.AdvanceTo(buffer.End);
            if (result.IsCompleted)
            {
              break;
            }
          }
        }
      });
      image.WriteToStream(innerPipe.Writer.AsStream(), ".png");
    }
    catch( Exception e )
    {
      logger.ZLogError(e, $"Error when generating image");
      using Image errorImage = Tile.CreateError(e);
      errorImage.WriteToStream(pipe.Writer.AsStream(), ".png");
    }
    finally
    {
      foreach( Image img in images )
        img.Dispose();
      await pipe.Writer.CompleteAsync();
    }
  });
  return Results.Stream(pipe.Reader.AsStream(), "image/png");
});

app.Run();