// Small NATS-over-WebSocket example for the deployed server.
//
//   dotnet run --project examples/csharp
//
// Env vars:
//   NATS_URL       default: wss://nats.tes.gd
//   NATS_USER      default: admin
//   NATS_PASSWORD  required

using System.Text;
using NATS.Client.Core;
using NATS.Client.JetStream;
using NATS.Client.JetStream.Models;

var url  = Environment.GetEnvironmentVariable("NATS_URL")      ?? "wss://nats.tes.gd";
var user = Environment.GetEnvironmentVariable("NATS_USER")     ?? "admin";
var pass = Environment.GetEnvironmentVariable("NATS_PASSWORD")
           ?? throw new InvalidOperationException("NATS_PASSWORD is required");

// 1. Connect. wss:// is understood natively; credentials go via AuthOpts.
var opts = new NatsOpts
{
    Url      = url,
    AuthOpts = new NatsAuthOpts { Username = user, Password = pass },
};
await using var nats = new NatsConnection(opts);
await nats.ConnectAsync();
Console.WriteLine($"connected  server={nats.ServerInfo?.Name}  version={nats.ServerInfo?.Version}  jetstream={nats.ServerInfo?.JetStreamAvailable}");

// 2. Core pub/sub — fire-and-forget events, no persistence.
var subject = $"demo.{Guid.NewGuid():N}";
using var subCts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
var subTask = Task.Run(async () =>
{
    await foreach (var msg in nats.SubscribeAsync<string>(subject, cancellationToken: subCts.Token))
    {
        Console.WriteLine($"core recv  subject={msg.Subject}  data=\"{msg.Data}\"");
        subCts.Cancel();
    }
});
await Task.Delay(200); // give the subscription a tick to register
await nats.PublishAsync(subject, "hello-core");
try { await subTask; } catch (OperationCanceledException) { }

// 3. JetStream — persistent events. Create a stream, publish a few, then read them back.
var js = new NatsJSContext(nats);
const string streamName = "DEMO_EVENTS";
await js.CreateOrUpdateStreamAsync(new StreamConfig(streamName, new[] { "events.>" }));

for (var i = 1; i <= 5; i++)
{
    var ack = await js.PublishAsync($"events.item.{i}", Encoding.UTF8.GetBytes($"payload-{i}"));
    Console.WriteLine($"js publish subject=events.item.{i}  seq={ack.Seq}");
}

// 4. Replay from the beginning with a fresh ephemeral consumer.
//    DeliverPolicy.All ignores prior consumers — you get every message in the stream.
var consumer = await js.CreateOrUpdateConsumerAsync(streamName, new ConsumerConfig
{
    Name          = $"replay-{Guid.NewGuid():N}",
    DeliverPolicy = ConsumerConfigDeliverPolicy.All,
    AckPolicy     = ConsumerConfigAckPolicy.Explicit,
});

var fetchOpts = new NatsJSFetchOpts { MaxMsgs = 10, Expires = TimeSpan.FromSeconds(2) };
await foreach (var msg in consumer.FetchAsync<byte[]>(opts: fetchOpts))
{
    Console.WriteLine($"js replay  seq={msg.Metadata?.Sequence.Stream}  data=\"{Encoding.UTF8.GetString(msg.Data!)}\"");
    await msg.AckAsync();
}

// 5. Clean up the demo stream so re-runs stay idempotent.
await js.DeleteStreamAsync(streamName);
Console.WriteLine("done");