using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Diagnostics.HealthChecks;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Diagnostics.HealthChecks;

namespace StellaOps.Worker.Health;

/// <summary>
/// Extension methods to add lightweight health endpoints to worker services.
/// </summary>
public static class WorkerHealthExtensions
{
    /// <summary>
    /// Registers a health check that tracks whether the host has fully started.
    /// Call this on <c>builder.Services</c> before building the application.
    /// </summary>
    public static IServiceCollection AddWorkerHealthChecks(this IServiceCollection services)
    {
        services.AddHealthChecks()
            .AddCheck<HostStartedHealthCheck>("host_started", tags: ["ready"]);
        return services;
    }

    /// <summary>
    /// Maps <c>/health/liveness</c> (always 200) and <c>/health/readiness</c>
    /// (checks registered health checks) endpoints.
    /// </summary>
    public static WebApplication MapWorkerHealthEndpoints(this WebApplication app)
    {
        // Liveness: always returns 200 if the process is running
        app.MapGet("/health/liveness", () => Results.Ok("Alive"))
            .ExcludeFromDescription();

        // Readiness: runs all registered health checks tagged "ready"
        app.MapHealthChecks("/health/readiness", new HealthCheckOptions
        {
            Predicate = check => check.Tags.Contains("ready"),
            ResultStatusCodes =
            {
                [HealthStatus.Healthy] = StatusCodes.Status200OK,
                [HealthStatus.Degraded] = StatusCodes.Status503ServiceUnavailable,
                [HealthStatus.Unhealthy] = StatusCodes.Status503ServiceUnavailable,
            },
        });

        return app;
    }
}