using System.Text.Json;
using FastEndpoints;

namespace SpaceGame.Api.Universe.Api;

public sealed class StreamWorldHandler(WorldService worldService) : EndpointWithoutRequest
{
  private static readonly JsonSerializerOptions SseJsonOptions = new(JsonSerializerDefaults.Web);

  public override void Configure()
  {
    Get("/api/world/stream");
    AllowAnonymous();
  }

  public override async Task HandleAsync(CancellationToken cancellationToken)
  {
    HttpContext.Response.Headers.Append("Cache-Control", "no-cache");
    HttpContext.Response.Headers.Append("Content-Type", "text/event-stream");

    var afterSequenceRaw = HttpContext.Request.Query["afterSequence"].ToString();
    _ = long.TryParse(afterSequenceRaw, out var afterSequence);

    var scopeKind = HttpContext.Request.Query["scopeKind"].ToString();
    if (string.IsNullOrWhiteSpace(scopeKind))
    {
      scopeKind = HttpContext.Request.Query["scope"].ToString();
    }

    if (string.IsNullOrWhiteSpace(scopeKind))
    {
      scopeKind = "universe";
    }

    var systemId = HttpContext.Request.Query["systemId"].ToString();
    var bubbleId = HttpContext.Request.Query["bubbleId"].ToString();
    var scope = new ObserverScope(
      scopeKind,
      string.IsNullOrWhiteSpace(systemId) ? null : systemId,
      string.IsNullOrWhiteSpace(bubbleId) ? null : bubbleId);
    var stream = worldService.Subscribe(scope, afterSequence, cancellationToken);

    await HttpContext.Response.WriteAsync(": connected\n\n", cancellationToken);
    await HttpContext.Response.Body.FlushAsync(cancellationToken);

    await foreach (var delta in stream.ReadAllAsync(cancellationToken))
    {
      var payload = JsonSerializer.Serialize(delta, SseJsonOptions);
      await HttpContext.Response.WriteAsync($"event: world-delta\ndata: {payload}\n\n", cancellationToken);
      await HttpContext.Response.Body.FlushAsync(cancellationToken);
    }
  }
}