using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;

namespace NATS.Server.Monitoring;

/// <summary>
/// HTTP monitoring server providing /healthz, /varz, and other monitoring endpoints.
/// Corresponds to Go server/monitor.go HTTP server setup.
/// </summary>
public sealed class MonitorServer : IAsyncDisposable
{
    private readonly WebApplication _app;
    private readonly ILogger<MonitorServer> _logger;

    public MonitorServer(NatsServer server, NatsOptions options, ILoggerFactory loggerFactory)
    {
        _logger = loggerFactory.CreateLogger<MonitorServer>();

        var builder = WebApplication.CreateSlimBuilder();
        builder.WebHost.UseUrls($"http://{options.MonitorHost}:{options.MonitorPort}");
        builder.Logging.ClearProviders();

        _app = builder.Build();
        var basePath = options.MonitorBasePath ?? "";

        var varzHandler = new VarzHandler(server, options);

        _app.MapGet(basePath + "/", () => Results.Ok(new
        {
            endpoints = new[]
            {
                "/varz", "/connz", "/healthz", "/routez",
                "/gatewayz", "/leafz", "/subz", "/accountz", "/jsz",
            },
        }));
        _app.MapGet(basePath + "/healthz", () => Results.Ok("ok"));
        _app.MapGet(basePath + "/varz", async () => Results.Ok(await varzHandler.HandleVarzAsync()));

        // Stubs for unimplemented endpoints
        _app.MapGet(basePath + "/routez", () => Results.Ok(new { }));
        _app.MapGet(basePath + "/gatewayz", () => Results.Ok(new { }));
        _app.MapGet(basePath + "/leafz", () => Results.Ok(new { }));
        _app.MapGet(basePath + "/subz", () => Results.Ok(new { }));
        _app.MapGet(basePath + "/subscriptionsz", () => Results.Ok(new { }));
        _app.MapGet(basePath + "/accountz", () => Results.Ok(new { }));
        _app.MapGet(basePath + "/accstatz", () => Results.Ok(new { }));
        _app.MapGet(basePath + "/jsz", () => Results.Ok(new { }));
    }

    public async Task StartAsync(CancellationToken ct)
    {
        await _app.StartAsync(ct);
        _logger.LogInformation("Monitoring listening on {Urls}", string.Join(", ", _app.Urls));
    }

    public async ValueTask DisposeAsync()
    {
        await _app.DisposeAsync();
    }
}